Buying a 91 6.2 suburban that's been garaged for 5 years,any advice?

[Dieselfume1]

Hey folks,

New to the forum. Looks like lots of good advice here.

I'm going to pickup a new to me 91 6.2 suburban in a couple days. I went up and test drove it a couple days back and will go back pick it up when I have some time off work.

The machine has been garage kept all of it's life, the paint is perfect and the interior has never seen children. the last 5 years it's only been driven about 50 miles once. Now for the bad part.

Odometer reads 265,000 mi.!

It was 15 degrees the day I went to look at it, and the owner had it plugged in (didn't get to see how it started cold). It popped right off and ran great. He said before he put away 5 years ago it had new injectors and new injection pump. The fuel filter is new as well.

When I drove it it seemed to drive good, had enough power to get itself up to 70 and stay there. could hardly tell it was a diesel when cruising at hwy speeds.!

Since this thing has been sitting so long, any other recommendations on this engine besides dumping the oil? I'm getting rid of my TBI suburban that's completely used up to go back in time to this box style diesel....
Hope I'm making the right decision.


Any advice on making this 6.2 live a long life? the owners I'm buying it from are elderly, so it's never seen hard driving, but quite alot of gravel roads where I'm from.

Thanks guys.

DF

[Robyn]

Hi, and WELCOME TO TDP :):):):)

The 91 was the best of the old square body trucks.

Sounds like you found a great deal.

265000 on the clock is not a death sentence by any means, with the worst case scenario being that you might want to consider replacing the head gaskets and bolts this summer if you have the time.

If you decide to do this, give a shout, and we can brief you on some of the few little oddities about these engines that can help avoid issues.

If the oil has been changed regularly the engine should be in pretty good shape.


One great indicator or the engines condition is to remove the oil filler cap with the engine idling.
You should not see huge amounts of blowby vapor,and what there is should clear quickly when raising the rpm slightly.

The 6.2 is a good reliable, long life engine.

Probably want to drop all the fluids and flush things and refill.
Change all filters
Drop the pan on the tranny, change filter, gasket and refill.
Even an extended flush of the tranny would be good as the converter can't be drained separately.

While the pan is down, look for any amounts of crud in the bottom.
Coolant hoses, fresh GREEN antifreeze (I would avoid the red stuff)

Belts and other little nick nacks can be freshened too.
Check the brakes and while your in there you can see if anything is leaking (seals)

A good drive to get everything up to temps should give a pretty clear story.

Post some pix of the new ride when you get her home.

Again, Welcome.

Missy

[DmaxMaverick]

Welcome aboard!

Very nice find! I agree with Robyn. Nothing really special, all regular maintenance items. At 265K, especially with such a long idle period, head gaskets are in order. They are "normal" maintenance items at 250K, anyway. And, while you're there, replace the water pump, timing set, balancer, and crank pulley (if it has the rubber-isolated pulley).

Essentially, any exposed rubber item on the truck is suspect. This includes body, engine, tranny and transfer case mounts, and spring/shackle bushings. All of these go a long way to keep the overall operation smooth. Hardened or failed rubber isolators will also cause excessive stress on the fasteners. You'd be amazed at how a truck can seem "new", with all new rubber. They weren't meant to last an eternity. Remember, anything that hasn't been replaced is over 20 years old. None of these are particularly expensive (or difficult to replace), but they do add up. You don't have to do all of them at once. Old tires suffer the same fate, even if they "look" good.

[Dvldog8793]

Howdy
I have had three older 6.2 trucks and all three had low miles. The only thing I would add to the "keep an eye on it" is rear main seal. They are a rope type seal and after heat cycles and sitting for long periods will get brittle and fall apart. Makes a real mess....
Sounds like a nice rig....
LMC truck has almost all the rubber parts that Dmax spoke of.
Good luck!

[AKMark]

If you are pulling the oil pan, with that many miles, I would put a new oil pump in it.

[john8662]

The oil seal on a 1991 is the updated seal and not a rope seal.

If there is a leak back there it's most likely the oil pan itself leaking where the RTV seals to the block and rubber seal on the rear main bearing cap.

J

[Dieselfume1]

so you're saying it's a one piece rear main like they put into their small/bigblocks?

Out of curiosity, why replace the headgaskets until they fail?

As for the timing chain, no doubt it's stretched, but if left unchanged, will it break? or is it something that can wait until the water pump goes out?

Getting excited to have this thing. Thinking about changing all the glow plugs out as a precautionary thing when I get it. Anything wrong with the fast reacting $60 per set stuff sold on ebay? What do you guys recommend?

Thanks,

DF

[DmaxMaverick]

Be wary of that Ebay stuff. Those "fast reacting $60 per set stuff sold on ebay" are junk. If you want a set of "Quick Heat" plugs, get them from kennedydiesel.com . A little more in cost, but they're backed by someone we know, and trust. I use them, and they've been good.

The head gaskets WILL fail (statistically) at some point. You choose the convenience if you do them as a maintenance item. They choose the (in)convenience if you don't.

The timing chain not only drives the valve train, but also the injection pump. As it stretches, the timing retards. You can compensate the pump timing, to a point, but as the chain wears, the departure between the crank, valve and pump timing increases. This affects power, economy, and starting. A rough-running engine is hard on other parts (like accessories and transmission). I've not heard of one breaking, but once they start to wear, they get worse quickly.

[Robyn]

The 91 does indeed use the one piece rear main, that's very similar to what the gassers use.

Don't really want to wait till head gaskets fail on these, as it can cause damage to the cyl block deck while it's in it's death throes, and it will never happen at an opportune time.

Also, when it blows it can seriously stress the radiator and heater core as things really get pressured then.

When doing head gaskets, always replace the bolts, as they are a TTY (TORQUE TO YIELD TYPE) one use and toss.

Also, the push rods must be kept in the orientation they are in when you open it up.

The end that's to the rockers must go back as the other end is not hardened.

The plastic rocker guide buttons need to be replaced as well.

The timing chain stretches and this fools with timing big time.

The sprockets are usually fine, and will be great for another go round, unless the teeth are worn, but usually they don't wear.

I would use a new style 6.5 head gasket set, as they have better fire rings, and the area near the end water ports are far stronger.

Use Felpro head gaskets and bolts.

Stay away from the cheap crap.

Felpro is not that bad, and they are good stuff

As mentioned, get the good glow plugs.

AC 60g are great, and won't swell, and they will stand abuse better.


Good luck with the new rig.

I'M JELLOUS :D

Missy

[Dieselfume1]

Well, She's home!

pulled my 06 Tahoe out of the garage to accommodate the new ride :D

My kids went nuts when they saw it! They can't believe how big it is!

The back end of the Sub sags a bit, but it's nothing that can't be remedied with a helper spring.

She ran flawless all the way home. Set the cruise on 70 and it never shifted down for a hill. When I step down on it it doesn't smoke at all the way I thought it might being N/A.

Picked up all the fluids and filters today to drop every oil in every compartment and re-fill. Gonna put a line pressure kit in the 4l60 to help the shifts a bit.

The engine I'm sure needs some glow plugs. when we started it up to leave (plugged in) it started a bit hard and smoked white out the passenger bank for a few seconds and then cleaned up quickly.

Just cannot believe how clean this machine is inside and out. will post pictures when it's washed up and clean.

[Dvldog8793]

AC60G are great plugs. I have tried a few of the others and always went to the 60g.

IMHO- don't bother with the helper springs...order some real 3/4 ton springs and put them in. Might ride a little rougher but by the time you get a full tank, and the family in you wont notice...:D

Sounds like a nice rig...

[Dieselfume1]

Just ordered a set of fast reacting plugs from Kennedy-

Sounds like those that have them like them for the stock glow plug controller. We will see. I'm praying to God that the old ones come out.

[trbankii]

order some real 3/4 ton springs and put them in.

I'm not seeing if you said it was 1/2 ton or 3/4 ton, but as you're going on 300K miles a new set of springs of either variety would probably be in order over just a band-aid of helper springs.

[Dieselfume1]

Well I feel like an idiot.

Took the burb down to the shop to look it over some more, finally got the pesky reserve tank hose clamp moved so I could get radiator cap off (couldn't remove it when I looked at it to buy it) and noticed the radiator was down a bit.


Filled it up, and the reserve tank. Started the engine with the cap off. as soon as she took, coolant puked out of the radiator immediately. when it settled down, I get a consistent bubbling out the filler neck. I've seen head gaskets out before when I used to work on truck engines for a living, and I believe this is it.. I could remove the thermostat and tell which gasket it out, but it doesn't matter much, might as well do them both and get it over with.

Do these heads typically crack? wondering if they should be pressure checked?


I'll get some prices on head gaskets , rocker guide buttons, and timing chain tomorrow. I was hoping to put this off for awhile. dang it.

May need some info on torque specs for head bolts and such in time. Thanks all for your help so far.

DF

[Dieselfume1]

http://www.prcforum.com/forum/attachments/2664d1395892565-new-ride-20140326_33.jpghttp://www.prcforum.com/forum/attachments/2664d1395892565-new-ride-20140326_33.jpghere's some pics... dirty I know, but all I have for now.

http://www.prcforum.com/forum/attachments/2662d1395892557-new-ride-20140326_31.jpghttp://www.prcforum.com/forum/attachments/2663d1395892561-new-ride-20140326_32.jpg

[Dieselfume1]

sorry for duplicate in last post.

http://www.prcforum.com/forum/attachments/2665d1395892569-new-ride-20140326_34.jpghttp://www.prcforum.com/forum/attachments/2661d1395892553-new-ride-20140326_28.jpg

[Dieselfume1]

So another question on replacing these head gaskets-


Noticed that last night the intake was full of crud from the EGR setup. I blocked the vacume hose to disable it, but I'm wondering if I can get non egr intake gaskets to block exhaust from the intake completely? What years were non EGR?

Thanks! DF

[Dvldog8793]

Howdy
Just find a NON EGR intake. Either open or dual plane. Both are fairly easy to find and cheap. They also Flow way better....Check your exhaust manifold on the driver side and disable the valve if it hasn't been already.

[DmaxMaverick]

All years had EGR, depending on the engine series. If yours has EGR, then it's a "C" code engine (8th digit of VIN).

If you are removing the EGR (for off highway use only, of course), it's best to replace the intake with a non-EGR, and be done with it. The manifolds aren't too costly, and usually available. Also eliminate (remove or "gut") the back-pressure valve in the exhaust, while you're at it. This will open the airways quite a bit, which is also a slight boost in economy and power.

In regards to the heads, yes. They do routinely crack. However, the cracks between the valves rarely cause issues or interfere with normal operation. As long as they don't cross the valve seats or leak coolant, they will be fine. Otherwise, replace them with a new set of modern castings, such as AM General or Clearwater. The AMG's are 100% new of improved design (same as supplied to the military), while Clearwater are new Chinese castings using recycled hardware. The AMG's are about $300 more, and you don't have to return the core.

[Dieselfume1]

Pulled thrermostat...

The passenger side had air coming out of the passage like an exhaust pipe.

after 3 hours this is what I uncovered-

http://www.prcforum.com/forum/attachments/2671d1395967806-new-ride-20140327_6.jpghttp://www.prcforum.com/forum/attachments/2672d1395967810-new-ride-20140327_7.jpgMassive crack on #6, and a crack somewhere one #4. It's been running this way awhile... got quite alot of pitting on both pistons, the head is all chewed up, and I've got some rust pitting on the cylinder bores.

Question is now what do I do? try and find a used head and hope the cylinder bores /piston rings are up to the challenge of making compression?

Forgot to mention, the pushrods on #6 were bent slightly, and both lifters were destroyed. the push rods had been driven into the lifters to the point of breaking the lifters. it took quite a bit of effort to get the pushrods out. I think I got all the pieces of the lifters.http://www.prcforum.com/forum/attachments/2673d1395967814-new-ride-20140327_9.jpg

[john8662]

Shoot.

Your next task is going to be finding another set of cylinder heads.

You can go a couple ways with this engine. Being this is a 1991 verify that the casting number on the heads ends in -567. If so your head options are easy. You can replace them with 6.5TD cylinder heads. The only difference will be the precup diameter (larger). Which will still be fine, will lose just a bit of mileage.

I'd clean this engine up with some different heads and run it for as long as it'll let you and in the mean time be looking for a replacement engine.

J

[Dvldog8793]

Not good...
Your post lists "somewhere up north" If you are in Northern MN I can maybe help with the engine parts. I live next door to a salvage yard that has more than a few 6.5.

[Dieselfume1]

Checked the bad head, it's a 567 head.

Got ahold of a friend of mine, he's got a good used 6.5 head on his workbench that he told me to come and get. mentioned I'd need to use my injectors though.... I don't plan on replacing the other head, but I think it may be wise to put a head gasket in it while everything's apart.

I may put the 6.5 head on the bank that's ok if it's a lower compression head... odds are the other bank that had the bad head has two cylinders now that are going to be short on compression.

Guess I could deck the head .010 on that side LOL

Are the 6.5 heads larger CC chambers?


Also if anyone has them I'd love to have the head bolt/ intake/ and injector torque values...

Thanks so much for the advice so far!

DF

[john8662]

If the head you're getting hasn't been milled, swap the precups from your bad head into the 6.5 head and you'll be set. If it has been milled, game over for the precups. Most shops mill the heads with the cups in the head (a no-no). They are supposed to protrude from the deck .001" - .003".

Everything else should be the same.

Pick up the Hayes Diesel manual, has the torque specs for these engines. Specs are also available for paid members in the members section.

New head bolts will have the torque specs and sequence. (20ft lbs., 50ft lbs. then 90 degrees) Replacing the head bolts is necessary.

You can also use the cheaper 6.5 head gaskets with your 567 heads, the 6.5 gasket is actually better (speaking Felpro here) If you wind up with Victor Reinz gaskets you'll be lowering your compression as they're NOT stock thickness.

J

[Dieselfume1]

got her started up tonight.

ended up pulling the drivers side head to inspect for peace of mind, and found that side had already been replaced with a 6.5 head. so, I put the 6.5 head I aquired on the bad side, and threw it back together. started up and runs good it seems, although at idle I'm noticing some white haze coming out the drivers side bank... don't know what that means exactly.

time will tell if the two bad cylinders I cleaned up will hold up or not. if I bring the engine just off of idle I can feel a slight miss, so we'll have to see how that progresses.

I'll finish buttoning her up tomorrow and take it for a test run.!

[Dieselfume1]

Started it up this morning again and found that I must have had a little air in the lines yet. once it bled off the thing ran great... I still have a little smoke, out both banks, but it's very light and I think only noticeable because it's in my shop running. No bubbles or compression in the cooling system either.

after it ran about 20 minutes while I did some chores, I cam back and did a cyl cutout test on every hole to make sure there wasn't anything missing. every hole was firing.

I did the test with the advance lever on the pump to see if it was too advanced or not, and when I push the plunger in the engine gets a little more of an aggressive rattle to it. maybe it's advanced too far?

The throttle response of these engines is amazing to me.

http://www.dieselbombers.com/images/buttons/edit.gif (http://www.dieselbombers.com/editpost.php?do=editpost&p=1056496) http://www.dieselbombers.com/images/buttons/quote.gif (http://www.dieselbombers.com/newreply.php?do=newreply&p=1056496) http://www.dieselbombers.com/images/buttons/multiquote_off.gif (http://www.dieselbombers.com/newreply.php?do=newreply&p=1056496) http://www.dieselbombers.com/images/buttons/quickreply.gif (http://www.dieselbombers.com/newreply.php?do=newreply&p=1056496)

[john8662]

Good to hear you got it buttoned up. Great amount of work in that project.

Will take awhile for everything to set in. At least it's a runner now and you can start planning on a replacement engine for down the road. But it will likely last that way quite a while.

J

[Dieselfume1]

Hey again guys, the engine's running good on this old burb, but a couple questions-

Sometimes when I go to start it hot the glow plugs wouldn't cycle. however it still started, just cranked longer. so, I bypassed what I thought was the "inhibit" switch? it's the one behind the ex manifold on the passenger side head.

Things had been working fine until yesterday morning. it was 25 degrees and I went to get the old girl started. I cranked and cranked and it smoked and smoked and wanted to fire, but acted as if it wasn't getting the glow plugs, even though the light was cycling... finally it did start, but I'm wondering, did I bypass the wrong switch?

Thanks!

DF

[DmaxMaverick]

On a warm engine, or when the weather is hot, it won't always cycle the GP's. That's normal. It shouldn't have to crank longer, however. Rather than "bypassing" the inhibit sender, you should install a GP override switch, which will allow you to glow at any time.

The reason for the hard start when cold sounds like lack of heat, likely not enough glow heat, or a too short cycle. If you're using AC60 plugs, this is expected. Either extend the glow cycle, or install an override switch to manually add glow time. Quick heat plugs do well, and don't require an extended glow time.

[Dieselfume1]

I've got the kennedy quick heats... which I'm betting are just 6v glow plugs.

[DmaxMaverick]

Most all civilian plugs are 6V. 12V plugs don't get near hot enough.

Kennedy QH plugs are about as good as they get, when it comes to getting very hot, very quick. You may have an issue with retarded timing, or the HPCA isn't working (you may have disabled it by bypassing the sender).

[john8662]

Hey again guys, the engine's running good on this old burb, but a couple questions-

Sometimes when I go to start it hot the glow plugs wouldn't cycle. however it still started, just cranked longer. so, I bypassed what I thought was the "inhibit" switch? it's the one behind the ex manifold on the passenger side head.



This switch is the Fast Idle and High Pressure Timing Advance switch. When closed gives you timing advance in the pump and energizes the fast idle solenoid.

You want this working.

If it's not starting well w/o the glow plugs check your cranking speed, possible dragging starter or weak batteries, it needs to crank fast w/o the glows working.

On the 1991 the glow plugs are inhibited/controlled by the computer. There is an additional relay next to the driver's side fender. This relay inhibits a pin on the glow plug controller keeping the controller from turning on. The PCM makes this determination based on the coolant temp sensor located on the thermostat housing passenger's side above cylinder #2.

Other than that, the PCM is used to control EGR and Transmission Lockup via the Throttle Position Sensor on the side of the IP.

Just more info for ya there...

[Dieselfume1]

Thanks guys

This thing I'm wondering now if it's a fuel issue.

thanks to you guys I found out the switch I had unhooked was the switch for the cold timing/throttle advance. hooked that back up. Tried to start it today at 40 degrees, and same blasted thing. crank and crank. white smoke out both sides till it fired.... once fired up it ran great. Took it to the shop, tested glow plugs. Glow plugs are coming on and off with the light. However, I'm not seeing that the cold advance is working. should the little plunger on the bottom of the IP be pulled in towards the pump when cold? or out? I can move it manually, but I don't think it's moving on its own.

What's strange is none of this was going on until I took it out to the shop the other night to put 2.5 inch lift blocks under the rear springs. since then I've got this cold start issue.

[john8662]

The cold advance can't be seen operating. The lever on the side of the pump controls timing advance based on throttle position and housing pressure, normal operating.

The HPCA as we call it, is a solenoid in the top cover of the injection pump. You can test this by unplugging the connector on the top of the injection pump (there are two, one is the fuel solenoid, the other the advance). Them, take a positive jumper wire and provide power to the connector, do this while it's running to if you hear the engine have more rattle (more advance).

Sounds like air in the fuel system is your problem.

Replace the rubber return line out of the injection pump with a piece of 1/4" clear hose. Observe bubbles while the engine running, also after the shuts down. If the hose drains back, you've got issues too.

J

[Dieselfume1]

picked up a check valve today to put into the fuel line between the filter base and the hard(feed) line coming from the fuel pump. Going to see if this keeps the fuel from bleeding off... I tried it to today. it fired right up, ran for 2 seconds and died out. restarted hard like it was out of fuel. I'm beginning to suspect the fuel filter base since nothing else has been disturbed except the lines going to and from the base. it's got a new filter on it too.

[john8662]

Check out the article at the top of the 6.2 forum about finding air in the fuel system.

Main point, make yourself a fuel cap with a tire valve stem in it for pressurizing the fuel tank some to find the fuel leaks.

[Dieselfume1]

Guys, just wanted to give you an update on the old girl, and to tell you all thanks again for the help getting it running

I've put on about 7,000 miles since aquiring and fixing the suburban right after I got it. It burns about a quart of oil every 700-1000 miles depending on how hard I push it. not too bad for having two holes that were pretty rough shape..

I put new tires on it, 31x10.50 r15 all terrains, lifted the rear axle 1.5 inches, and it looks good!

Everything in it works, it uses ZERO coolant.

Power is lacking, if you stick it into a 20 mph headwind it'll max out at 65.

it NEVER smokes, and I have plans to turn up the injection pump soon.

Mileage driving 70 mph averages between 14.5-17.

Starts good so far (it's summer) except for the rare occasion on a cold morning where the glows come on, and I forget or get side tracked an it starts the short cycle glows. when that happens I always have a hard start. or when the engine has been running maybe an hour prior, has cooled off enough to need the glows, but the engine is warm enough to only let the glows short cycle. those are hard starts too.

Thinking of wiring in a hot wire to a push button on the dash that is scotch locked into the harness that controls the glow control relay.

a few times this summer I had my "water in fuel light come on" I'd drain the filter, and go on, then it'd come on again 50 miles later. so I'd change the filter. so I decided to run the tank nearly empty to try and get as much water out of the fuel as I could. changed fuel filter again and haven't had a problem since.

Winter is coming on here soon so we will soon see how well the glow plug system is really working.

As for the trans, I rebuilt it myself due to a planetary failure right after I had all the engine trouble earlier in the year. it was my first time and it went pretty well! while I was there, I also discovered that the transmission was pushing fluid into the transfer case because of a bad seal. so I replaced that too. changed diff oils while I was at it :D

Since I had the suburban for so little time previous to this, I didn't really get a feel for the normal shift points before I tore the trans down.

Now that it's rebuilt, the tv cable is new, and adjusted properly,
the 1-2 shift hits at about 25, the 2-3 at about 38 and the 3-4 at about 52.

what really bugs me is the downshift. it won't kick down from OD to pass unless I shift it manually, or get down to about 48 mph.

Every shift is good and firm and otherwise shifts drives, and the tcc lockup works like it should. The torque converter was not new, but off of a used 94 4l60e trans (mine) that failed 30K after a rebuild from a slipping forward clutch.

it's been my experience with other 700r4s that anytime the acc pedal was flatfooted it always shifts out of OD, no matter the speed. only exception was for law enforcement vehicles. were the diesels this way too?

This sub has 3.73 gears, with 31 inch rubber. don't know what kind of effect that might play?

Maybe I'm worrying about nothing?

Thanks again for all the help guys!

[DmaxMaverick]

Sounds great! It's always nice when things just work.

Now, to clean up a few rough edges (in no particular order)....

If you're getting no black smoke at all during hard acceleration, the pump could probably use a little turn of the fuel screw. Don't get greedy unless you have an EGT gage. No more than 1/8th turn at a time.

3.73 gears and 31x10.50 rubber was OEM for many models, so nothing unusual there. Shortening the gears a bit will help with power, but it also increases the noise at highway speeds. Should be no hit to mileage, though.

The WIF lamp does more than just suggest water in the filter. It also suggests a pressure differential, usually meaning a plugged filter. The next time you drain the "water" from the filter, capture what you drain into a clear jar and cap it tightly. Let it sit for a couple hours, and see if there is actually water in it. After a long period of not running, other crud can build up (or grow) in the tank, which will eventually make its way to the filter.

An override button for the GP's should take care of your hard warm starts, and may help in the winter.

If it doesn't downshift from OD at WOT, the TV cable is not adjusted properly. Also, I'm surprised you've had success with the 4L60 converter. The ones I've seen used weren't worth the money saved. They weren't designed for the Diesel RPM range. It may have something to do with your no-downshift issue, but I'm not sure.

[Dvldog8793]

Howdy
Just a side note....Stay away from scotch locks. Take the time and do a good real splice into the line. a scotch lock basically just cuts you insulation and weakens/cuts the wire making a persfect point for "issues" in the future. I've seen more problems than I can remember caused by them in the ESV field when I worked at Motorola....
Sounds like a nice rig coming together...What pump series is it?

[Dieselfume1]

Thanks for the advice guys.

I'm not sure what series of IP it's got, It's fully mechanical, that's all I know and the pump and IP supposedly were changed right before I bought it. Didn't find out till later from a neighbor that the reason the previous owners changed it was because they accidently filled the tank with gas and drove it till it didn't want to run anymore (about 5 mi)

The 4l60e TC a friend at the trans shop told me is almost identical to the diesel unit except for it has 3 mounting pads for the flywheel instead of 6. he said there's no way that a 6.2 will ever have enough power to rip the 3 pads off of the TC. the lockup speed he told me is about 100 rpm difference. won't even be able to feel it.

I had about $250 in a transmission kit, and wasn't going to put any more into the transmission of a vehicle that was starting to look like a really deep money pit!

Wondering if I have a piece of junk in the throttling valve? the valve body was the only part I didn't tear down when I did the trans overhaul.

The tv cable I adjusted to be fully extended when the pump is at wot. only thing I'm wondering is, if I'm actually getting full throttle from the pedal in the cab? guess I need to get some help to hold it to the floor and see if it's actually getting full throttle.


I replaced all the rubber fuel lines going to and from the transfer pump, also replaced the transfer pump and put a check valve in the line after the fuel filter. none of this helped the hard start problem I was having this spring. but, since I've put a pile of miles on it this summer it's not had any hard starts to speak of that wasn't glow plug related, and I've been running a pile of power service and lucas fuel conditioner through it.

I put some oem aluminum 15 inch wheels on it and man it looks good. gets lots of looks as this "survivor" drives though town.

I've got a banks pyro I had on another vehicle, I could throw it on there, and try turning the IP up a little. My duramax has no problems at 1300 degrees, how about the 6.2s?

[Dieselfume1]

here's some updated pics of the old girl-

http://www.prcforum.com/forum/attachments/6558d1413464705-new-ride-sub1.jpghttp://www.prcforum.com/forum/attachments/6557d1413464688-new-ride-sub2.jpg

[john8662]

I've got a banks pyro I had on another vehicle, I could throw it on there, and try turning the IP up a little. My duramax has no problems at 1300 degrees, how about the 6.2s?

The 6.2 and 6.5 will not hold together at 1300 degrees.

For maximum power you may want to get your Maximum EGT's to around 1000. 1100 is the working limit for the 6.2. No anodized piston crowns.

With 6.5 heads you have a little more room for improvement verses the prior head design (different injector angle and pre-cups).

The no-smoke part is great.

Those rims above are my absolute favorite design wheel ever, I grab every set I can find locally.

J

[DmaxMaverick]

Thanks for the advice guys.

I'm not sure what series of IP it's got, It's fully mechanical, that's all I know and the pump and IP supposedly were changed right before I bought it. Didn't find out till later from a neighbor that the reason the previous owners changed it was because they accidently filled the tank with gas and drove it till it didn't want to run anymore (about 5 mi)

The pump is not the reason it quit, and may still be (or was) good. Diesel engines don't like gasoline, and after a certain mix ratio, the gas simply just doesn't ignite. 5 miles of normal driving is about enough to dilute the residual mix and cool the chambers so the fuel won't burn. Replacing the gas in the system with Diesel fuel would have very likely returned it to its previous running condition.


The 4l60e TC a friend at the trans shop told me is almost identical to the diesel unit except for it has 3 mounting pads for the flywheel instead of 6. he said there's no way that a 6.2 will ever have enough power to rip the 3 pads off of the TC. the lockup speed he told me is about 100 rpm difference. won't even be able to feel it.......They are different. There is a very good reason for 6 bolts, and they DO matter. Low RPM, high torque. If the TC doesn't break, the flex plate will. And, there's NO TCC lock difference, with any TCC converter. Lockup is determined by external electrical input (and ECM, on some models), internal electrical switch (valve body) input, and governor hydraulic input. The TC clutch is only a hydraulic slave, controlled by a solenoid valve mounted to the tranny housing, with nothing internal to the converter controlling it. Also, the no-downshift issue may be related to the higher stall speed of the TC. The TCC should unlock at WOT, and if the stall is too high, it won't allow the load to force a downshift. Or, it could be a combination of both causing the issue. Your tranny guy either forgot how they work, or he should get a refund on his tuition.


Wondering if I have a piece of junk in the throttling valve? the valve body was the only part I didn't tear down when I did the trans overhaul.

The tv cable I adjusted to be fully extended when the pump is at wot. only thing I'm wondering is, if I'm actually getting full throttle from the pedal in the cab? guess I need to get some help to hold it to the floor and see if it's actually getting full throttle......TV cable adjustment:
Zero throttle input, press button on side of bracket, which should retract the adjuster. Engine off, have a helper MASH the pedal to the floor, and hold it there. This will adjust the cable. Then, with it still at WOT, try to move the throttle shaft bellcrank. It should be stationary, with no movement in either direction. If it allows for increased throttle, the throttle cable is bad, the bracket, at either end, is bent/broken/worn, or something is interfering with the pedal, but NOT a problem with the TV cable. The TV cable itself is passive, and only moves according to throttle input. Adjust/repair as necessary, then repeat the adjustment and test.


I've got a banks pyro I had on another vehicle, I could throw it on there, and try turning the IP up a little. My duramax has no problems at 1300 degrees, how about the 6.2s?I'd use it, no doubt. 1000 typical, 1100 max, as John said. Unless you really like Play-Dough pistons.

[john8662]

Don't worry about the 3-lug design on the torque converter. Just be sure you used at least RED loctite on the threads.

The 6-lug 700R4 converter is considered obsolete. I inquired about this through several converter manufacturers. The 3-lug design actually has stronger lugs on the converter. The old 6-lug design lugs were not as securely mounted. Both converter shops I dealt with said they would not weld on the old 6-lug cover nor add lugs to a 3-lug converter due to warping, which would affect the already very little they can take off the clutch facing surface inside the converter front cover (lug side).

My little 82 that makes over 700 ft. lbs torque is using a 3-lug converter. I had to use the better loctite as it did start working loose and damaged the flexplate. If I could of relied upon a 6-lug converter I would, they're simply not a viable option though.

You're fine with the 4L60E converter, even with the little bit higher stall speed.

The Stall speed should not affect downshift.

Most likely an issue with the TV circuit in the valve body. I've got a trans in a truck now that has the same problem, and that transmission has been gone through. The problem kinda went away after rebuild, but came back.

Be interested in what you find out there. I've been starting to research it. I don't mess with the internals of a transmission, only a few valve body modifications.

J

[Yukon6.2]

Nice Sub
I had to sell my parents Sub that was in pristine condition.I would have kept it if it had been a diesel.
It was red/white with red interior,local guy bought it and is keeping it in great shape.I fantasize about the day he decides to sell it i may have to bring it back home.
Thomas

[Dieselfume1]

Don't worry about the 3-lug design on the torque converter. Just be sure you used at least RED loctite on the threads.

The 6-lug 700R4 converter is considered obsolete. I inquired about this through several converter manufacturers. The 3-lug design actually has stronger lugs on the converter. The old 6-lug design lugs were not as securely mounted. Both converter shops I dealt with said they would not weld on the old 6-lug cover nor add lugs to a 3-lug converter due to warping, which would affect the already very little they can take off the clutch facing surface inside the converter front cover (lug side).

My little 82 that makes over 700 ft. lbs torque is using a 3-lug converter. I had to use the better loctite as it did start working loose and damaged the flexplate. If I could of relied upon a 6-lug converter I would, they're simply not a viable option though.

You're fine with the 4L60E converter, even with the little bit higher stall speed.

The Stall speed should not affect downshift.

Most likely an issue with the TV circuit in the valve body. I've got a trans in a truck now that has the same problem, and that transmission has been gone through. The problem kinda went away after rebuild, but came back.

Be interested in what you find out there. I've been starting to research it. I don't mess with the internals of a transmission, only a few valve body modifications.

J


I'm just about to go take out the governer out of the tailhousing, and start grinding on the weights the bring the shift point up. I know I don't have a pressure problem, the tv cable it set properly (checked it last night) the shifts are good and firm, so I know it's not a pressure issue....

Do any of your guys's 4 speed transmissions shift down at highway speed? 65/70 mph? I'm not sure if they're supposed to or not!

[crashz]

Beautiful Sub! Those were my favorite years with the aluminum wheels and 90/91 grills.

[DmaxMaverick]

I'm just about to go take out the governer out of the tailhousing, and start grinding on the weights the bring the shift point up. I know I don't have a pressure problem, the tv cable it set properly (checked it last night) the shifts are good and firm, so I know it's not a pressure issue....

Do any of your guys's 4 speed transmissions shift down at highway speed? 65/70 mph? I'm not sure if they're supposed to or not!

I don't think grinding on the flyweights would be a good idea. Get your hands on a gasser governor (beg, borrow, steal) for a test, if all you want to do is "move" the shift points. Maybe try a different ATF. Modern synthetics and Dexron VI are lighter oils than conventional Dexron III ATF (which is no longer certified for use in GM autos). If the ECM is still in the loop, the TPS must be working and properly adjusted. If not, the TC won't unlock when it should, and may prevent a WOT downshift.

A downshift at that speed would also be dependent on the final drive ratio. It may be normal. Maybe not. 3.73 and 31" rubber should downshift at 65, but there may be other factors involved. Is the tranny original? Rebuilt? Replaced (with older)?

[Dieselfume1]

a diesel has a tps sensor? I thought that was what the kickdown cable was for? I can feel the transmission unlock when I begin to step down on it, and lock back up when I step out of it, so I know that parts working.

I rebuilt the transmission this winter after finding lots of steel in the pan. had a planet getting ready to bust loose on me. works great after rebuilding it, just don't know if it shifted this way before or not, I only put about 50 miles on it before I went into it.

[trbankii]

a diesel has a tps sensor?

TPS - throttle position sensor.

[Dieselfume1]

I know what they are and what they do. never seen one on a mechanical engine.

[DmaxMaverick]

TPS = Throttle Position Switch (not Sensor, in this case). Similar appearance, different function.

ECM (Emission Control Module) equipped trucks, such as CA and a few other regions, require this for EGR and TCC command. It switches at idle and WOT positions, for ECM input. A "C" code engine with "non federal" smog should have one. I think (not certain) 1988 "C" models all had the ECM, CA smog or not, if it has EGR. Earlier "J" codes used a simple collapsible circuit for TCC. If the ECM and/or TCC has been bypassed or tossed, it does nothing. If the switch is removed (or out of adjustment) with ECM control still in place, it will cause issues. The TH700R4 doesn't require electronic input to operate, but the TCC may if the ECM is still in control (it actually has a logic board). Later models (like 1991) won't downshift with the TC locked. The earlier models may have been the same, but it's been over 20 years since I've seen one still stock, or working originally. The TCC hydraulic circuit will inhibit the TV command to downshift if the TC doesn't unlock. Federal smog models may be different, but I don't know why they would be, and I don't recall. The 88-91 GM truck, SUV and Diesel models was one big grey area mess, full of inconsistencies. GM tooling transition years since 1981 have always been that way, it seems.

The ECM is an EPA device, and should be treated as such, whatever that means to you. If it, or any input dependency devices, have been bypassed, removed or otherwise eliminated, they all need to be eliminated or accommodated. They're designed like a 3-legged stool.

HD models with TH400 tranny will have a vacuum switch in the same location (for vacuum modulator). This may not be relevant to your situation, but it's caused a lot of confusion over the years during pump replacements, when LD and HD lines are crossed. They can all be accommodated, but when you don't know what you don't know, things can get nerve racking.

[Dieselfume1]

dang, that's just great.

I disabled the egr by plugging up the vacume line to the egr valve. the check engine light goes on and off as I drive. figured it had to do with that.

As for lockup, if it was't coming unlocked, when I slow from hwy speeds to a stop shouldn't my transmission stay in 2nd gear? or would it be more likely if the ecm isn't working right that it doesn't lockup at all?

The computer is working, but I'd love to dump it all together. the goofy glow plug cycling while warm is another reason.

any way I can fool the computer into thinking the egr is working? I have no idea how it knows wheather or not that vacume line is plugged or not.

Maybe I need to take an old egr valve and hook it up to it on the firewall somewhere so it thinks it's doing something.?

I'm not against wiring up a lockup switch either.

[DmaxMaverick]

The ECM doesn't control the glow plug cycle. It ONLY controls the EGR, EPR and TCC. Nothing else on the 91. The ECM doesn't actually monitor the EGR, but the solenoid feedback. The GP controller is independent of any other system.

If you have disabled the EGR, you might as well disable the entire ECM system. Get a pre-ECM diagram and wire it accordingly, with the collapsible circuit for TCC. There are also other ways, such as a fully manual TC control, like mine is. I went so far as to bypass all the internal tranny switches, so it locks as soon as it shifts to 2nd gear, and won't unlock until it shifts back to 1st, or I unlock it manually.

The TPS, if it isn't forcing an unlock at WOT, won't have any affect with unlock at lower speeds, when it isn't WOT. The hydraulic circuit (governor and gear range) will force an unlock before stopping. However, if it is working at zero throttle, some model years and series will cause an unlock when coasting. Another EPA condition, but one that I've always hated, and another reason for my fully manual control mod. Having more effective compression braking is much more important to me than anything the EPA thinks I need.

[Dieselfume1]

you're saying that if the egr's disabled it renders the rest of the system inoperable? that just sounds goofy..

When I had the transmission apart, I recall the tcc lockup solenoid, and another hookup that I believe was for a transmission temperature switch. think it was a single wire towards the rear of the trans.

so by theory, if I shut the ecm down, unplug it, it renders the transmission fully manual except that I won't havel lockup without manually wiring it.

As for the glow plug controller, I thought the ecm used engine temperature to inhibit the glows while the engine was warm? isn't that the reason for the two wire coolant switch on the upper coolant manifold?

I'm not going to enable the egr system spent to much time cleaning carbon out of the intake on this thing the last time I had it apart.... I may check codes on it today and see if it's just the egr code that's showing and not something else. maybe I left something unplugged?

far as I know the trans had been locking and unlocking, I can feel it.

sorry guys, this has been frustrating.lol

[DmaxMaverick]

you're saying that if the egr's disabled it renders the rest of the system inoperable? that just sounds goofy.

No, not necessarily. If you only plug the vacuum line, it won't do anything for the rest of the system, although it may prevent EPR operation.


When I had the transmission apart, I recall the tcc lockup solenoid, and another hookup that I believe was for a transmission temperature switch. think it was a single wire towards the rear of the trans.I'm not aware of a temp switch/sender at the rear. Speed sensor, yes.


so by theory, if I shut the ecm down, unplug it, it renders the transmission fully manual except that I won't havel lockup without manually wiring it.Just unplugging the ECM will prevent lockup and EGR operation, but I don't know what else may not work. This is why I suggest rewiring the harness according to a previous HD, non-ECM truck.


As for the glow plug controller, I thought the ecm used engine temperature to inhibit the glows while the engine was warm? isn't that the reason for the two wire coolant switch on the upper coolant manifold?This is only true for 1994+ trucks. The 85-93 models have the temperature inhibit built into the controller mounted above the valve cover. Adding a manual GP switch into the system is simple, and works. The GP system can be either completely manual, or you can have manual operation along with the original automatic system. The ECM may use the coolant temp to inhibit TCC (and perhaps EGR) until ECT is high enough, but that's about it.


I'm not going to enable the egr system spent to much time cleaning carbon out of the intake on this thing the last time I had it apart.... I may check codes on it today and see if it's just the egr code that's showing and not something else. maybe I left something unplugged?The oily mess is caused by the CDR, then turned into an oily-gooey mess by the addition of the EGR. It doesn't really hurt anything, but is messy. Any petro-based solvent cleans it up pretty easy. OTC degreasers don't work. Messy job, for sure. I drop the intake into a tub of #2 for a couple days, then finish it up with Simple Green or Gunk Engine Cleaner. Dawn and hot water works, too, but takes too long. Stopping the EGR will make it less gooey, but it will still be oily.

Reading codes is always a good idea, and it's simple, even if you don't have a code reader. If you are intent on disabling the ECM, don't worry about what it "thinks", as it won't matter once it's no longer functional.


far as I know the trans had been locking and unlocking, I can feel it.The problem is the downshift, which may be related to TCC unlock. This is different from normal upshift TCC, which may seem to operate normal, otherwise.


sorry guys, this has been frustrating.lol

No doubt. Long-distant troubleshooting can be equally frustrating. But, we stick with it.

[Dieselfume1]

well had enough time today to play with the burb a little bit.

I took the cover off of the IP, turned the screw in 1/8 of a turn. IP is a DB 2829 for whatever that means.

Then I checked trouble codes, and I had code 12 which I'd guess is "all clear".

While the glow plugs were cycling I test light probed the pink wire on the glow plug relay which is hot when the glow plugs are turned on. I believe that's the wire turning on the relay, so I'll most likely tap into that with my manual override later on...

I meant to find an old egr valve to hookup to the egr solenoid to see if I could fool the ecm into thinking it was doing something.... if that worked, all I'd have to do is gut the EPR (leave it hooked up) and things should work.

We'll see how it goes.

[john8662]

Respectfully, Dmax is wrong about the ECM and the glow plugs on a 1991 Burb. There is an additional relay on the driver's fender that inhibits the glow plug controller based on ECT reported to the ECM.

You'll find a coolant temp sensor located on the thermostat water crossover, this reports to the ECM for the glow plugs. Again, this is not a n/c switch, it's an actual sensor.

Defeating this inhibit system for glows, I haven't tried. The controller still has some logic on temperature as well (when it won't turn them on as well).

The ECM also controlls the Torque Converter lockup. Look-up (search the forum) for procedures on testing and adjusting the Throttle Position Sensor on the 6.2 (or the 92-93 6.5TD for that matter as well), same procedure.

If this sensor is out of range, you won't get a lockup. It will fault and you just won't get lockup unless it's where it needs to be. Which is near .5 volt at idle and 5 volt at Open Throttle.

The 89-91 Suburbans and Blazers are a little different from previous 6.2's electrically. I don't know if these same things apply to the GMT400 6.2's (I suspect they do), but they do the square body.

So, the 1991 C/K1500 series Sub w/700R4 the ECM controls:

TCC, EGR, EPR, Glow Plugs (inhibit only)

It's possible I can reprogram one of these ECM's to disable the EGR. I need to see what prom is in the box. I have a 1991 6.2 C1500 burb in the family, so I'd have to ask I can take the ECM out and play.

[Dieselfume1]

Cooler weather is coming on again, and the suburban is starting to act just as it did last year when things cooled off. I have to believe it's a glow problem, but I'm unsure. I'm going to wire in a manual switch this week hopefully, so we'll see.

How long should my glows be coming on initially? It just seems like my cycles are shorter than they should be, and it's impossible to "double glow" them with this computer system.

Suggestions?

Here's a video of exactly what it's doing. this is at 40degrees F, after a night at about 30 degrees.

https://www.youtube.com/watch?v=v_EqN2PcEM4

[Yukon6.2]

Nice truck
I remember mine would do that on occasion.My fixes were....
1st fix was air getting into the system through the rectangle filter housing,one of the small plugs was corroded and leaked,i cleaned it up and cut threads in it and installed a threaded plug.
2nd fix was replace plugs that were not working.
My glow time is pretty close to yours and i am starting at -10C without any trouble,if i don't keep my foot on the accelerator for a few seconds sometimes it will stumble and quit.I might be getting a little air in the system through my clear hose,it has gotten hard over the last few years.
I don't think you have a computer in the glow circuit,I'm thinking just a relay as a timer.
Thomas

[Dieselfume1]

Thanks Thomas,

I replaced all thefuel lines this spring, and didn't change anything. if it is indeed a fuel problem, then I might just junk that filter base. 35 bucks a filter is too much anyway.

[john8662]

The glow plug controller itself controls the duration of glow, the computer in your 1991 only controls whether to allow the controller to start it's process (inhibit function only).

Unfortunately, there isn't really a way to change the controller externally for glow duration. There were some things that could be done internally, but this will take some digging to find.

So, I watched your video. That's a very poor start.

You're getting great cranking speed, so your starter and batteries are working well.

The glow duration seems a little short if that was indeed the first glow you gave it (looked like it was). I'd suggest replacing the glow plug controller. The timings are all internal, it also senses temperature, so it could be malfunctioning from that perspective.

With your start I see three potential problems:

1) Short Glow Duration and poorly performing plugs
2) Air in fuel system, drainback
3) Possible High Pressure Cold Advance/Fast Idle inoperative

Fix for number one, replace controller and verify plugs. I strongly recommend the Kennedy Quick Heat plugs, these work extremely well with stock glow times. Night and Day difference in starting performance.

Fix for number two, find a way to pressurize the fuel system from the tank on and look for weeping line connections. Use your eyes and nose to find the leak. Also possible bad fuel tank cap allowing the generation of too much vacuum in the tank which will cause a drainback condition. Replace the fuel cap with a new Diesel Fuel Only cap.

Fix for number three, test HPCA/Fast Idle circuit. Bone cold, turn on the ignition and don't start the engine. Take a 12v test light and test the power lead on both the fast idle solenoid on the injection pump and the HPCA connector on the injection pump for power. If no voltage, the HPCA/Fast idle switch (located on the passenger's cylinder head, rear behind cylinder #8) has failed, and you need a replacement.

[Dieselfume1]

Hey John

Yep, that was the first start of the day. glow time initially is about 6 seconds. I have brand new kennedy quick heats installed in the unit, and I noticed no change in the starting. (all the old glows worked)

I ordered a new filter base today (spin on) since I've already replaced all the rubber fuel lines on it. I'll try a new fuel cap too.

I'll check the cold advance also. I take it the smaller wire on top of the IP is the one that controls the cold advance? not the red power wire?

Thanks,

DF

[john8662]

Hey John

I'll check the cold advance also. I take it the smaller wire on top of the IP is the one that controls the cold advance? not the red power wire?



Yep, small wire, top cover.

I wouldn't jump to replacing the fuel filter housing, just yet. For testing, sure.

[joeq]

Hello DF, Looks like you've got some miles out of this thread. Nice looking Burb. I'll have to admit, I haven't read all the responses, but was curious about your cold start problem. I'm sure there's a lot of good advice being thrown at you, and if I could, I'ld like to contribute, if you don't mind.
I just watched your video, and noticed you didn't give the glow plugs much time to cycle. Plus you were cranking, while they were cycling. My 6.2 doesn't ever start on 1st cranks, when it's cold out. When my controller "used to" work, years ago, I found it better to wait for it to cycle on and off, a few times, B4 cranking. And the amount of time that you kept cranking your motor, trying to lite it off, was a little excessive. It really works that starter doing that. It doesn't take very long, to heat up your cables. Go out and feel them sometime, while someone else is cranking. Not sure if you've read your manual for cold cranking, or what your method is, but it says to floor it at 1st to get the fuel into it.
The most successful starting procedure I've learned on my truck over these past 22 years is this. Not sure if you'll be as successful, because my system is a little different. I've by-passed my controller, (due to cost reasons), and have it connected to a spring loaded switch on the dash. So I'm able to apply it a little differently than the controller does. also, this is when the OAT is less than 50* or so, and no block heater.
Key on, push glow plugs on for 5 sec., release for 5, and push on again for 5 seconds, then release. Immediately floor the throttle, and crank for less than 10 seconds. It may burp, but usually won't start.
2nd attempt- cycle glow plugs again twice, at 5 second intervals, and this time, when cranking, don't give it any fuel. Sometimes it'll light off, if not pump the throttle lightly, and see if it starts. 90% of the time, it will start.
If not, cycle the plugs, 1 more time, then it'll start.
It sounds tedious and time consuming, but sitting there grinding on the starter till it starts is awful on your starter. And of course, if you plug in your block heater, it'll start like it's 70* outside, even tho it's 30*.
So in your situation, don't know if you've tried this, but let your plugs cycle a few times, till they basically stop, then crank it with a full throttle. If no dice, try it one more time, and hopefully it'll go. If nothing else, please be kind to your starter. They are in a very cruel environment with these 6.2s.
If you abuse it, it will end up looking like this.
http://i1206.photobucket.com/albums/bb453/tajoe/Shed%20build/83%20duelly/JDand62starter014_zps055a02c1.jpg (http://s1206.photobucket.com/user/tajoe/media/Shed%20build/83%20duelly/JDand62starter014_zps055a02c1.jpg.html)

[Dieselfume1]

Thanks Joe,

I'll try letting it cycle and see if it helps.

When I start it I flat foot the accelerator pedal like the starting instructions above the visor indicate.

All the years we had 6.5s it always seemed like they fired best if you fired the immediatly after the first long glow went off. but I was pretty young then and I don't really know if we tried it the way you suggested.

As for the long cranking. I generally don't stick with it that long because I know how hot it gets the starter. It wouldn't bother me to let it try to fire off the first time, stop cranking, re-glow it, and try again except that the factory controller only comes on for about 1 second after the initial glows.

Today I picked up a new racor fuel filter base/5 micron filter. I also got a new fuel cap, and a momentary glow plug switch. We'll try them out and see what happens.

Thanks for putting your 2 cents in, I'm always open to advice especially from folks who've been able to get along with these beasts for so long!

DF

[Dieselfume1]

tried letting it cycle continually before starting, and it didn't start any better. maybe even worse.

Tonight I put on a new fuel filter base w/5 micron fuel filter included from racor through car quest. total cost $80.

got it fired up and took it for a drive. seemed for some reason like it had more power, but it could've just been the change in the weather.

we've got a blast of arctic air coming in tonight and is gonna stick around for about 7 days. I'll know tomorrow whether or not the fuel filter base was the culprit in all this.

if nothing changes, I'm going to put in the glow override switch next and see what happens.

[Dieselfume1]

ok, have tried thew new fuel cap, new filter base and tried starting last night at 10 degrees. no fire. plugged it in for 2 hours, fired up fairly well. still took a couple shots of the glow plugs before it'd stay running. If I have time I'm going to wire up the glow controller's manual override button and see how it goes. gonna be below zero tonight. we'll see how it goes.

[john8662]

Was the HPCA working?

Any smell of Diesel, or wet throttle shaft on the injection pump itself?

Did you install a piece of 1/4" clear line on the injection pump? hint: you won't find fuel rated line, just any clear tubing at the hardware store will work.

Did you install thicker head gaskets during your engine work?

Still think your glow controller is giving you too short of cycle as well, extending your glow time will certainly help if that's the case. You can glow those KD plugs for longer bursts. I've done them with 20 second glow times on my low compression engine to start.

[Dieselfume1]

Didn't remember to check the HPCA. no fuel leaks or smell of fuel

I didn't install any clear tubing. I may in the future for troubleshooting purposes, but it doesn't seem that I have a fuel problem. I have all kinds of smoke when trying to start this thing up. it's the getting fire I'm seeming to have trouble with.

I attempted to put a bypass switch in tonight for the glow plugs, but I didn't realize that the timer setup was integrated into the glow plug solenoid. doesn't appear any way to "trick it" into glowing with a manual button. Looks like a ford starter solenoid is in my future.

Might check the HPCA tomorrow.

Great to hear I can glow the kennedy quick heats longer. a friend of mine who's owned only 6.2s/6.5s all his life tells me that there was never a glow controller built for the 6.2 that was any good. they all need a manual ovverride switch for more glow time. he suggested 3 seconds on, 3 seconds off, for 3 cycles, then start.

for head gaskets, I put in victor reinz. a mistake I know. I requested fel pro's from the parts store, but they got in the victors, I was in to big of a hurry to make them send them back, plus, I figured this engine was on borrowed time as is.

[AKMark]

I went to quick heats on the 6.5 I owned and found the factory glow cycle was too short once temps dropped below 30.

I set up the factory unit to trigger an aftermarket relay, then added a momentary switch that allowed me to trigger it longer.

I would typically not use the switch until the rig didn't start on the first try. It was fun pressing the little button, after a few seconds you could hear popping sounds as the unburned fuel in the cylinders ignited as the glow plugs got hot enough.

On both of my 6.2's there's only the relay and momentary trigger. I find that typically if I count to 8, they fire right up. I typically give both rigs another couple glow shots if it's below zero just to help them stabilize. I don't know offhand what glow plugs they are running since both haven't required any maintenance in that area other than getting rid of nonfunctional factory relays.

[john8662]

Depends on which VR gasket you used. The 6.2 one is great. The 6.5 one is thicker that it should be for stock, leads to a drop in compression. Besides that's they're fine.

Thinking a compression test would be in order soon enough, that will tell the tale there.

If you find low compression (around 350 psi or lower) then you will need to look into momentary push button relay for glow times in the 15 second or so time to get dependable starts in the cold.

Besides that, injectors that are leaking will bleed down and cause hard starting as well, not real common but possible.

[Dieselfume1]

well, then I made a mistake then, I've got 6.5 VR gaskets on my 6.2

So, I'm sure I've got a compression problem.

A strange thing has happened on this machine

A few days back I ditch the oem filter base in favor of a aftermarket fuelwater seperator (5 micron). at the same time the fuel heater and water in fuel light was unhooked as well. noticed an immediate increase in power.

A couple days ago I had a day off so I decided to take the beast into town to run some errands(50 miles) To my amazement, the transmission problem I had (not shifting down from OD to 3rd at WOT ) is now fixed. If I gun it it downshifts and takes off.! Would a low power situation cause the transmission not to shift down? I re-checked the kickdown cable and it's perfect as it was before. nothing's changed there. The only thing I've done is ditch the fuel filter base. only other thing I can figure is that it's been colder than a wedge (below zero for going on 3 days strait) and that might have free'd up something that was stuck in the valve body?


Got the manual glow plug override switch in tonight and working. was super easy and cheap. I didn't plug it in tonight, and I'll try to fire it in the morning to see if using the manual glows will make a difference.

Thanks again for you help guys
!

[Dieselfume1]

Success!

Can't believe after all this time and money spent, the whole problem all along was insufficient glow time.

After dropping the fuel tank to replace fuel lines that weren't bad, replacing the filter base, replacing the lift pump and all the glow plugs, the solution ended up being a $15 relay, $10 worth of cables, a $5 switch and about 30 minutes of time.

Glow on 8 sec, off 3, on 5, ignition. bam, starts. I imagine it'll need more when the temps drop below freezing again, but usually when a diesel starts this well at 5 degress, it'll still start fine at -15

[Yukon6.2]

Right On
It seems like there might of been some restriction in the old base or filter.You should investigate a bit to see if you can find anything to confirm that.
-22 C here last night,i'm going to try to start my truck today,not plugged in so the Optimas will get a work out.
Thomas

[john8662]

Bad glow plug controller as mentioned earlier, too short of glow time.

Your 8 seconds you could have automatically with a good controller.

Low compression 6.2's and 6.5's will start well when manually glowed longer.

I think the transmission issue is too much clearance on the TV valve bore in the valve body. I spoke at length with a local trans guy about the 700. I specifically mentioned this sluggish if no kickdown out of overdrive. He said that was the issue. The only fix for it was to bore and sleeve or if not that bad drill out slightly larger a port in the separator plate to allow more fluid flow out of the relief port.

Cold outside, thicker fluid, makes up for the TV leakage.

Still worth checking on the cold advance working.

[Dieselfume1]

Well after putting some more miles on the old girl I think things are as good as their going to get.

With the manual controller it starts every time in temps of 10 degrees or above on the first try.

When it gets colder than that, usually zero or colder it doesn't matter how long I glow it, the engine doesn't have enough compression left IMO to kick over. with out glowing and cranking 4 times or so.

It was -10 the night before last, I took this video

https://www.youtube.com/watch?v=STSW8zoiR00

The video is 4-5 minutes long. and after I shut the video down, it picked up one of the weak cylinders on the RH bank. (starts loping then picks the cyl up completely followed by a minute or so of what sounds like piston slap/spark knock.)

My IP timing is about two line widths advanced. Right where the the last people that put the IP on it left it, and scribed a line. must have been done by someone with a timing meter.

The problem with the not shifting into OD at WOT came back when the warm weather came back, and I haven't had the energy to take it on. I did however install a TC lockup switch. It's been one of the best things I've done. The TC was locking and unlocking on its own, but when you put it into a stiff wind (15-30 mph) it would run unlocked all the way home (50 mi). the switch lets me lock it up and forget about it.

Mileage has been elusive. 11-14 had been average through the winter, the last couple 200 mile round trips I made driving half interstate half 2 lane of speeds between 70-80 mph, I got 17 mpg. half of that was going into a 10mph wind.

Having increased timing should help the MPG right?

I don't feel my tires are too big, but it almost acts like that.

It's got 3.73s with 31x10.50r15s on it.

someday I might have to try and drive it at 60-65 mph and see what it can do. I'm sure having a almost 300,000 mile engine with 2 weak cylinders doesn't help the mileage situation.

Am I missing anything that I can do to optimize this old girl?

I'm preparing for the worst, when this engine lets go. I've located a "known running" 83 6.2 that came out of a pickup that someone is willing to trade me for some small block chevy parts. it'd be nice to have a spare engine sitting there with fresh head gaskets ready to drop in if this one decides to scatter.

[AKMark]

My 6.2's would get about 22-24 mpg when keeping the speed below 60. My 6.5's got about 17-19, but I was going 65-70 most of those times.

The old Diesels aren't the greatest for speeds above 60.