another engine died thread

[Subzilla]

My 2-week-new-to-me '94 6.5 has been showing codes 32, 33, & 74 and will stumble between 30 and 50 on heavy acceleration. Last weekend, it actually had multiple stalling out sessions every minute on my commute home. I installed a new Dtech/cooler behind the bumper and the stalling went away.

However, the stumbling still exists. AND just moments ago, I had it idling in the driveway and it died. It will not restart or even pretend like it's going to restart. Just like someone pulled the plug. Went to pull the codes and all I get is 12 continuously. Nope, it's not OK. The other codes went away.

Where do I start?:mad:

[Subzilla]

OK, found a very slightly loose cable on the driver's side battery. Tightened it. Cranked on it another 10 seconds. Nothing. Cranked another 10 seconds, it starts to catch for another 5 seconds, then she fires up. Idles smooth as silk and just drove it for 5 minutes with no stumble or stall. I didn't get up to highway speed so I'm guessing the 30 - 50 stall may still be there.

Pulled the codes and get the 32, 33, and 74 again.

Recranked and let it idle for a few minutes just fine.

Any clue what just happened?:confused:

I haven't changed the fuel filter yet. 6 Baldwins are on order and should be here tomorrow.

[Robyn]

Be sure that the two small wires that come from the main harness at the back of the engine and bolt to the intake manifold are in good order.

A poor ground here will really foul things up, or a broken wire.

Be sure that the shut off solenoid is working properly. These can fail and cause intermitent problems.

Stumbling can be due to AIR in the fuel. Get a clear plastic line on the return fitting at the top of the IP.

Run the engine a bit to clear the line out. If you see a stream of bubbles you need to find out where its coming from and fix it.

Air will drive these things nuts.

How much fuel is in the tank when this happened. The pickup assembly in the tank has a Bypass unit that will allow the engine to get fuel even if the SOCK gets plugged.
The bypass can leak air, and when the fuel level gets below that valve it will suck air.

If the tank is better than 1/2 it should not do it.
Check for air bubbles in the return line and then proceed.


Missy

[Subzilla]

Tank is near full.

I did see the wires attached to the intake manifold. I'll trace them down to make sure they are good.

Will check the shutoff solenoid and throw in the clear line to check for air. Already have one cut just for this purpose!

Thanks!

[rameye]

I vote for air infiltration on this one...just dealt with it..made me crazy!

[Subzilla]

Checked the fuel shutoff solenoid, seems to click normal with the ignition
switch.

Clear return line on the IP showed no air after the initial air stream purged out. I stared at the line for 5 minutes at engine idle. Revved it up and still saw no air. Maybe it's somehow getting an intermittent air burst somehow??

Replaced fuel filter last night and the old filter didn't "look" that bad at all. Test drove it and got it to stumble only one time after 15 minutes of driving. I can't seem to get a constant pattern like I first thought I had. Still a little paranoid about driving it to work (don't want to break down in rush hour traffic!) so I don't know just how bad the stumbling may get.

May drive it around tonight to better check it out.

Still getting the 32, 33 and 74 codes. Haven't done anything to eliminate those.

[JohnC]

Faulty EGR can cause missing as can an intermittent oil pressure switch.

[Subzilla]

John, I was wondering about the EGR codes and the OPS. Also, previous owner said he installed a non-GM OPS. The oil pressure always seems to read low and I know the right OPS to install should be a GM version.

Drove the thing today and the stumbling just seems to be so random. The first 15 minutes it drove just dandy. Then from a stop light, it stuttered, so I goosed a little more just see what it would do. It really stumbled but still accellerated. For the next 5 minutes at 60 mph, it would fishbite every minute or so. Then for the final 20 minutes of the drive, it was fine. Lots of idle time at stop lights but never died.

Last night, the wife drove it. She said it stumble only once but on a restart during her errand run, it died at idle. It restarted after a few seconds but then it ran fine.

One other sympton, the thing is always hard to start, even when warm. Takes a few seconds of cranking, even when hot. Haven't gone through the GP system yet other than to pull 3 of the newly installed plugs. They tested good but are the Autolite brand. Plan to replace those with the better ones.

Change out the OPS with the GM version?

Block off the EGR? Will it still throw codes?

[ToddMeister]

To disable the EGR just pull the vacuum line off the EGR valve and plug the end of the vacuum line. The EGR valve should stay closed.

Oil Pressure switch could be intermittent causing the lift pump to run erratically.

I'd replace with the GM version, also put in an auxillary relay to power the lift pump instead of thru the OPS

[Subzilla]

New update: Started engine to go home, idled for a minute then died. Took several cranks to get started.

Started light stumbling within a few miles, then while sitting at stoplight, it had 2 major surge burst. Scared the poopy out of me. Then it started running rough but no smoke. Started to accelerate and it had half the power that it should have. Drove another 3 miles like this, then it died. Was able to get out of the street into a parking lot.

Tried to restart and she wasn't going to do it. Called AAA. While waiting, I noticed a puddle of diesel fuel and could see a drip every few seconds. Looked like it was coming from right about the middle back of the engine. Intermittent fuel line air leak turned into a larger opening causing my troubles??

Got the thing home, crawled under it and could see where the fuel had made it's way into the TC cover. Strange thing, I inspected all the fuel lines, took the 2 bolts out of the fuel manager to look all around it and could NOT see where any fuel had been leaking or spraying out!! I figured it must have come from this area to make it's way down the to the TC cover. Now I could not see the lines that snake from the fuel pump next to the firewall up to the fuel manager. Possibility??

Getting dark and the engine was still hot and I got tired of burning my arms so I gave up for the night.

Any thoughts??

[DmaxMaverick]

If you have fuel leaking from the TC cover, the source is likely from the pump, pump supply line, or the fuel manager. Fuel leaks in that area drain through the valley and into the TC cover. All of these are downstream of the fuel lift pump, so it should not be stalling unless you are losing more fuel than needed by the pump. This should be rather significant, and more than just one puddle noticed on the roadside. Perhaps a leak coupled with an intermittent/dysfunctional lift pump?? Also check your return lines for leaks, but these shouldn't won't the stalling.

[JohnC]

There are 2 short rubber lines, 5 or so inches long, right where the hard lines on the bell housing cross under the sharp edge (iirc) of the firewall to the engine block. these are behind and below the fuel manager. If the hard lines are not properly secured to the bell housing they will rub on the firewall and eventually leak.

Another thing that is known to cause "fish biting" is a faulty optical filter harness right off the optical sensor on the pump. It can be eliminated, at least for troubleshooting.

[arveetek]

The symptoms you have sure sound like classic fuel delivery problems. The sudden surging is common with air getting in the system.

Now, to find the source of the problem....

Casey

[Subzilla]

Thanks for the replies. I'm planning to do some exploratory surgery on it this weekend. It does act like air in the fuel issues.

I'll report my findings.

I bought this, my first 6.5, for a good price knowing it had some issues. I'm experiencing some quick on the job training in the first month of owning it and I'm trying not to get too discouraged or frustrated. Not quite as simple to diagnose as my 6.2 critters.

[Subzilla]

Tore everything apart and found multiple potential problem causing issues.

First, the FFM heater appears to be leaking where the 2 wires protrude out. I've read the fix is to replace. Saw one online for $70.

Fuel line at IP is loose enough to freely twist around. No fuel appears to have leaked but I'm sure it sucked air in.

Inlet fuel line to FFM was also loose. Another air sucker.

Previous mechanic (probably responsible for above) for some reason decided to remove the drain line and drain "T" fitting. He put a screw into the rubber line then clamped it. This also looks weapy.

All of the above lines are very hard and very old. Not sure why previous mechanic/owner wouldn't have replaced them with the new IP/engine replacement done 50k miles ago.

FFM orings look OK, may have been leaking but can't really tell.

Found complete take-off FFM, new, at Pennisular Diesel for $85 plus $15 shipping/tax. Not a bad price!

Now the decision. Reading on the forum I see lots of conversions to the Racor 230R2. Found one on line for $115. Only $15 more than the new factory model. Now weighing the options of factory vs. Racor. The Racor doesn't have the heater. I'm trying to decide if I would need the heater here in NC. My Sub has never had one (the 6.2 on-line heater is gone) and I've never had any issues.

I can't seem to find the price for the Racor heater on line. Any clue on prices? Could I use the same factory heater lines to run the Racor heater?

What about the water sensor? What happens if left unplugged? Is the the sight bowl good enough if checked every time the hood is open?

Thanks!

[Subzilla]

Found some of my answers after I posted. Sorry, should have researched the forum first.

Leaving water sensor plug dangling won't harm anything or trip the light.

It seems the need for the fuel filter heater is not that great unless it's really cold. Getting below the 20's in the winter is very rare here in NC. Again, never had any trouble with the Sub on this.

Really leaning toward the Racor. It's very apparent how Robyn feels about the factory FFM! Something about throwing it, kicking it, abusing it..........:eek:

[DmaxMaverick]

Correct, you don't "need" the WIF sensor. The circuit is normally open, so if it's disconnected, the system will not see a problem. If you have a sight bowl, you are ahead of the game (as long as you look at it once in a while). You can visually detect water in the fuel LONG before the WIF would have ever indicated it. By the time you get enough water in there to trigger the sensor, you're about a New York minute away from "almost there" to "crap, too much".

The fuel heater doesn't do anything for system-wide temperature issues. It will only help the fuel already in the filter, with gelling or waxing before and during a cold start. It won't prevent this from happening anywhere else in the system, or after it is running. It offers some benefit, but not nearly what one might think. Once the engine is running, fuel circulation will heat the fuel in the tank and lines. By the time temperature becomes a concern, you should be running fuel treated for the condition.

I agree with Robyn, in regards to the fuel manager. There are better options available. A simple test (also applies to the PMD and a few other components): Remove it and throw it far into a large body of water (pond, lake, ocean). If it floats, it's good.

[Subzilla]

I plan to disable the EGR by plugging the vacuum line. Does it matter which intake manifold gaskets I have? EGR block-off plate or not?

I still plan to test the lift pump to make sure this is not also causing problems.

Got the new GM OPS in the mail last night.

Ordered the Racor filter housing. Should be here this week.

[Lug]

Also check your fuel delivery pressure from the lift pump. Just had one die a couple of weeks ago and it was causing stumbling issues as well. I used an old school vacuum/pressure gauge for a carb. tuneup kit to measure fuel pressure. The OEM style of lift pump seems to not have a good longevity reputation. Also make sure the power wires along with the grounds are all good. Mine was down for a year because of a less then tight connection of the pcm power wire on the firewall. It doesn't take much of a voltage drop (appears to be less then 1 volt in my case) to make the pcm not function right.
Justin

[Subzilla]

Lug, I may have your problem.

Got my new Racor 230R2 mounted on the driver's side firewall with all new fuel hoses to and from it. Pieced everything else back together. Installed new AC Delco OPS.

Opened the filter vent, fired up the electric pump and quickly saw the bowl fill up but didn't come out the vent. Opened the Racor pump and proceeded to hand pump thinking that might do the trick. Still no fuel at the top of the filter. Went back and forth between the electric pump and hand pump for the next 15 minutes and saw no fuel at the top of the filter/vent.

Truck "should" have plenty of fuel as I filled it up and the trip odometer reads 280 miles. I believe the odometer is accurate. On a 34 gallon tank, I "should" be able to get 400 to 500 miles?? This was my first tank full on the new to me truck so I don't the its personality yet. Funny thing is the gas gauge does read close to empty. This doesn't seem to be accurate.

Just for fun, I cracked the injector lines and could not get them to weep. (although it made me start to weep!)

Haven't checked the pump outflow or the supply line to the pump. Next step??

If the electric pump is not working, why wouldn't the filter hand pump not prime up?

[rameye]

Thats an easy one Sub....you have air infiltration aft of the pump.

This pump need to be able to create a vacuum in order to get fuel to it.....if you have a "hole in the straw" you wont get fuel to the pump and it wont come out the fuel filter....this goes for any pump that draws liquid against gravity.

In other words you most likely have a leak between the tank and the pump...they don't always weep so it'll be a dickens to find. This might also explain some of your earlier troubles.

my .02

[Subzilla]

That's what I'm thinking. Either that or clogged fuel tank sock. I guess if it were a bad lift pump, the Racor filter hand pump should have pulled some fuel up??

I had about 15 minutes of free time last night to undo the line at the filter and kick on the pump. It spit out fuel a couple of times and then nothing.

I think I will connect the lift pump on the suction side with a line running into a container of diesel and kick on the pump - just to verify its operation.

Then go looking for a leak toward the tank. I sure hope it's not "drop the fuel tank" time!! Could I apply slight air pressure with an air hose into the fuel line, then listen for any hissing?

[rameye]

I dont think pressurizing the line will buy you anything....

Dropping the tank sucks,,,but not terrible either....just bothersome.

You wont be able to save the lines...zero slack...just cut'm and be done

[DmaxMaverick]

If you have to get to the top of the tank, remove the bed. It's WAY easier than dropping the tank. If after the bed is removed, you still have to remove the tank, it's a walk in the park. It's easier to remove the bed then drop the tank, than just dropping the tank. Anyone who says otherwise has been doing it wrong, or has never done it.

[rameye]

Dmax is right ...IF you have a pick-up!!! Suburban is a whole different kettle o fish.

I wouldnt reccomend lifting the body :}

[Subzilla]

Yea, I keep seeing Dmax's recommendation for removing the bed in other posts! Ain't never done that before but am willing to do things that make life easier. Time seems to be my missing key element here. Haven't been able to touch the thing in a few days and the next 4 or 5 are not looking any better.

Will explore the lines and pump with a microscope just to make sure there's nothing obvious.

Always something!:o

[rameye]

Dmax is pretty knowledgable...if he says its easier...it probably is..

I dont know if it can be done alone however (doubt it)...depends what kinds of back-up you have. I did the tank drop...solo.

[DmaxMaverick]

Yeah. Don't try to lift the body for a tank problem. Many model years of the Suburban have a trap door under the carpet for tank-top access (not sure about the 94, but if it doesn't, make one the first time you have an issue). Otherwise, dropping a Sub tank isn't too bad.

Lifting a truck bed is a piece of cake. I can do it solo about as fast as with help (or faster, depending on the help). If you have a garage with exposed rafters, that's the easiest. Detach the fuel filler, remove the taillights and tailgate (and any other things that might be attached to lessen the weight), then remove the nuts/bolts. Attach straps to each corner stake pocket slot (motorcycle straps, ratchet straps, etc, new or in good shape, of course) and suspend from a rafter/beam above each corner. Take up a couple inches at a time, at each corner as you walk around. The bed isn't that heavy, and most any adult can easily get a couple inches at a time. Continue until it clears, and roll the truck out from under it. I've done this on numerous year models under a bunch of conditions. Once, I just drove in some T-Posts (in a field) at each corner and used motorcycle straps to lift it. A little wobbly, but it worked in a pinch. Getting it back on is just as easy. Just don't try to get too much at one time, and it goes smooth.

While you're in there, hit the frame and everything with a pressure washer. Touch up any bare metal areas with some paint or undercoating. Clean up that ugly trailer wiring or whatever else should need attention. It will NEVER be this easy.

Add to that...... In an emergency (need a part and have no other way to get it, rush the kid to the ER, ran out of beer, etc.) the truck is still drivable (as drivable as it was before). Can't do that with the tank sitting on the ground.

[Subzilla]

Got a few minutes to tinker last night so I disconnect the line at the back of the fuel pump and throw on a rubber line with the other end in a container of diesel. Put power to the pump and it seemed to flow a considerable amount of fuel to the filter (had this line into another container). So it appears the fuel pump is good but still not wanting to pull fuel from the tank.

Strange thing, when I disconnected the line at the pump, I heard a vacuum sucking noise - like the fuel tank air space had contracted due to cold air temperature. Later, after I got everything back together, I removed the fuel cap and heard the same vacuum hissing.

If I had a leak in the lines, how would this airtight situation occur? Seems like my problem is more in the tank with either a clogged pick-up or something else??

BTW, to eliminate a bad fuel cap, I removed the cap and kicked on the pump - still no fuel flow.

May try to pull the bed off Saturday. Got some other critical chores to do first.

[JohnC]

Without going back and re-reading everything, and at the risk of asking a stupid question, is there fuel in the tank?

A guy I worked with spent the better part of a day troubleshooting a no start. Finally decided the in-tank fuel pump was bad. Pulled it out to find the tank empty. Replaced the tank gauge sender (stuck on 3/4) and all was well...

[Subzilla]

Well, I think. Had this happen to me in my Sub just a few months ago. Replaced filters and spent a few hours trying to diagnose an "empty tank". :o The thought crossed my mind numerous times for this problem.

The truck is new to me as of a month ago so I'm learning its personality. I filled it up and it now only has 250 miles on the odometer when all of this happened. It should be a 34 gallon tank so I would expect to get another 200 miles on the tank?? Funny thing, the gage does seem to read toward empty now.

Could there be something funky going on with the pick-up tube in the tank. I was even wondering if someone installed the wrong sender/pick-up tube.

I will for sure add 5 gallons worth to the tank and see what happens.

[rgrowan]

I have a '99 6.5 and I had all of the same problems you describe. I'm no mechanic or expert on these things, but I replaced the fuel pump in mine and the problem went away. No more "stumbling" or "bucking" and nice smooth acceleration. It was about 1200 bucks and 2 days at my fire station, but wasn't difficult by any means. Just have to be slow and methodical.

[rgrowan]

just to clarify, I meant injector pump...Told you I'm not an expert!

[JohnC]

Never verified this, but there's supposed to be a "fail safe" on the pickup tube that takes fuel from higher up in the tank when the strainer gets clogged. Could be your strainer is clogged or the fail safe is stuck open.

[Subzilla]

Yup, John, did some TDP post research and saw the issues with the fail safe valve on the pick-up tube being open and engine stalling at 1/3 tankfull. I threw in 6 gallons of diesel last night, kicked on the pump and out comes a nice steady stream of diesel!! Yes! So it was sort of out of fuel, I suppose, at least to the level where the tube is picking it up.

But again, I only show 250 miles on this tank. So that tells me there is something funky with the pick-up tube. I plan to top it off tonight just to see how much fuel I used for 250 miles. I want to make sure it runs properly before I pop off the bed and dig into the tank. I am really curious now!

Will let ya'll know what I find.

[Subzilla]

Ok, I just had another idiot light come on --- the one on my forehead. :mad:

Yes John, it was out of fuel! Put in 24.7 gallons of diesel over the weekend and it's been running fine ever since. But I will blame my shameful mistake on some assumptions I had made. And yes, I know what assume means when you break it down.

Assumption #1: the truck had a 34 gallon tank. Somewhere I thought I read that shortbeds had 25 gallon tank and long beds/shortbed extended cabs had 34 gallon tank. Looked up the dimension on LMC truck and it said all short beds had 25 gallon with length of 46" (34 gallon is 59" long). Measured mine to be 46"! So I have 25 gallon tank on my shortbed extended cab.

Assumption #2: Truck should be getting 17ish mpg. The truck is new to me and this my first time running out a full tank. The odometer showed 260 when it died. Do the math and that's like 10.5 mpg!! Whoa, something's not right with this picture. Gotta start going down the "horrible mileage" diagnostic list.

Assumption #3: trip odometer showed 260 miles so it should have plenty of fuel left even it had a 25 gallon tank. See assumptions #1 & #2 above.

With the new Racor filter housing (old one leaking), new fuel line, new AC/Delco OPS (to replace cheap aftermarket one), new PMD and cooler (needed a spare) AND a full tank of fuel, the truck now starts and runs fairly well!

[JohnC]

Yup, tank's under the bed. Short bed, short tank...

Now to the real problem, 10 mpg....

[Subzilla]

Ran through 2 tanks of fuel since the new fuel filter/housing install and fuel line replacements. 17.4 mpg and 17.8 mpg!! Now that's more like it. I must have had a really, really bad leak to have caused the 10.5 mpg and the empty fuel tank. The only time I really noticed the leak is when she died and we were waiting for the tow truck. There was a nice pool of fuel on the asphalt, I bet a good drink can full. It may have been really pouring out while driving, don't know. Another contributing factor to the bad mileage may have been that I was accellerating harder multiple times just to see how it was running and to try to duplicate the stumbling.

Anyway, it has been running without a hiccup since. Got some other things to diagnose and I'll post those as I get to them.

[JohnC]

"Time has resumed its shape. All is as it was before..."