intermittant surge

[catmandoo]

i have a 92 1500 2wd 5spd that has developed a wierd surge. i can drive around town all day no problem and i can drive on the hiway no problem and say if i come to a stopsign on the hiway and slow down to say 30 and push in clutch and stop and take off again no problem,but when i have a half mile or so say downward grade or flat and push clutch in and coast that 1/2 mile when i take off i'll get to just about time to shift and it will throw you back in the seat press in clutch and shift and it's still pulling even without my foot on the pedal but then seems to go away and then its fine.and also just today i noticed a slight kinda miss and it also seems to act retarded no power .any ideas?

[britannic]

Check your CDR valve is working correctly and that the return lines aren't restricted, including the one to the tank. If they check out then it's on to the lift and injection pump.

My truck would take off by itself when I coasted down hills and to stops, in my case it turned out to be a sticking CDR valve letting too much oil vapor into the engine where it produced some power.

[catmandoo]

what do you mean by cdr valve guess i'm somewhat in the dark there. truck has 360,000, 120,000 on new crate motor and new pump not rebuilt, so kinda somewhat suspect of pump but it runs and starts great cold ,hot whatever and runs perfect until i coast for 1/2 mile or so

[britannic]

CDR=Crankcase Depression Regulator, it uses the modest vacuum formed between the air filter and valves to keep a mild vacuum on the crankcase.

If it stops working properly, it will allow too much oil vapor into intake manifold and it starts burning in the combustion chambers. This might be the source of the symptom your seeing. My CDR packed up and I had power surges after the throttle was closed; a new one cured the problem.

[catmandoo]

well pulled cdr today and it had a film of oil in it like you dumped oil in it and then dumped it out other than that it was spotless in side so put new one in and 30 miles down the road it surged again from stop sign. am i looking at pump rebuild?

[britannic]

Before you condemn the pump, try one more thing to eliminate oil vapor as a cause by physically disconnecting the hose. Be sure to block off the CDR inlet so it doesn't aspirate dust laden air.

It's possible for the oil baffle to come loose and allow gobs of oil to get through and overload the CDR valve.

Did the symptoms initially improve after replacing the CDR? Is the symptom consistent and if so, would it have normally happened immediately after the CDR replacement?

[catmandoo]

well i didn't notice much of a change as i said it only does it when i coast to a stop seems i have to coast for say 1/3 to half mile but then it doesn't always surge but thats when i get it the most and just the other day it did it after it sat and idled for about 2 minutes.i was told by someone that it could be a high spot on the governor that it pops over to give the surge then it has to pop back and that will give a lag which i sometimes experience after it does it thenagain sometimes when it surges and i shift it still pulls its weird kinda has a mind of it's own i'd like to get it fixed before i put my turbo on one thing i did notice when i changed the cdr is i could look into the valve cover and there was kinda like brillo pad stuff on both sides of the hole but i could see clear to the bottom should that be completely covered if so maybe it is sucking up lots of oil.i don't have any other motors new enough my others have the cdr next to the oilfill pipe on the front.

[britannic]

Sounds like new/rebuilt inj. pump time...

[catmandoo]

is the baffle suppose to cover the hole in the valvecover to the point you can't see bottom. if so it's gone.

[catmandoo]

also i asked this over on the 6.5 section but it was originally a 6.2 on the water pipe by the thermostat is a tag which says use line to line timing only blah blah blah. 2 questions what is line to line timing is that just lining up the 2 marks on the pump and if so there is almost a 1/4 inch between them the pump is pulled to the driverside of the motor which i believe is advanced it's been like this since i got it and it's run great i average 26 mpg on the road and i've put 26000 miles on since march i hate to mess with it unless i could be some of the problem the motor now has 134000 on it maybe timing chain time?

[britannic]

The baffle is in the timing case on the 6.2L engine that uses the oil filler CDR outlet. Your 6.5L engine uses the valve cover, so the baffle doesn't apply, since there isn't a chain and gears flinging oil up the spout as it were :D .

A 1/4" is between the timing lines is quite a lot, but with the miles on the engine and your excellent MPG, it's probably OK.

Something is dumping extra fuel into the engine, so once you've eliminated all of the other possibilities, it leaves the pump as the most likely source.

[britannic]

One other thing, if you have an EGR system on that motor, check this post from Coghlin on the 6.5L forum:


Also pull your upper intake manifold and clean it out. I did this with my truck and two intake ports were almost completely blocked. THis is because of your EGR system. At idle when you plug in your wastegate actuator it should move the wastegate. It just might be possible for a sooty blockage to absorb oil vapor and then start dripping it into the cylinders once it's saturated.

[catmandoo]

well if there is anything in there i'll be damned the intake is probably one of the cleanest i've seen its not spotless it does have a little residue in it and the egr is unhooked what it kinda acts like is when started cold it really hammers for about the first 30 seconds or so give or take is this the retard mode for cold starts after this it just instantly changes to a quieter rattle.it kinda acts like its going back to this when it does it.it gets louder could it be going back and forth one other thing i did notice 2 days ago is right after it did it and i got into 3rd and everything was back to normal it had like the only way i can describe it a plugwire miss for maybe a second or so and came out of it and never did it again.acted like it was only 1 cyl doing it.

[britannic]

During a cold start the HPCA (High Pressure Cold Advance) valve is forced open on the pump to lower the return circuit pressure and advance the timing by about 6 degrees.

If the HPCA becomes faulty, or the return circuit is plugged and/or leaking so that the timing is inconsistent, strange drivability problems can result.

Since the problem you have is potentially dangerous, IMHO it would be highly advisable to have the pump checked and if necessary repaired.

[ 07-30-2003, 09:43 AM: Message edited by: britannic ]

[arveetek]

Sounds to me like it's getting air into the system. Air getting into the pump can cause surging, missing, and excessive diesel clatter. I would check for cracked fuel hoses, and maybe replace the fuel lift pump before condemning the injection pump.

Casey

[catmandoo]

think i'll try a pump the guy i got it from bought it new and can't ever remember replacing it, so if he didn't that 360000 on the pump. a diesel shop here also said something about the pump . think i got quoted 90.00 some odd dollars for a pump, must be made out of gold.i'll let ya know what happens

[arveetek]

Are you talking about an injection pump or lift pump?

$90 is a lot of money for a lift pump. You can pick one up at any auto supply for around $30 or less.

However, $90 is nothing for an injection pump. A rebuilt pump typically costs $175 to $350. A new inejction pump is several hundred.

Surely you're talking about the lift pump.

Casey

[arveetek]

I just looked again and realized that you have a '92. You have the electric fuel lift pump engergized by the oil pressure switch. This is a common 6.5L problem. I'm sure that the electric pump probably does cost a lot more. You might check out the 6.5L forum for more fuel lift pump questions and tips.

Casey

[catmandoo]

yes it is externally mounted and i got them down to 83. anyway it somewhat helped maybe 20 minutes after i changed it drivin down th road and came to a corner turned downshifted to 2nd and took off at about 30 or so it started to surge again but not as bad then 3 miles down the road topped a hill and coasted 1/2 mile to a stop sign and took off and no problem ran it up to 20 in first it usually does it about 15, shifted and everything workin good 15 miles down road coasted about 3/4 of a mile this time took off and still no problem then on the way back came to stop after coasting 1/2 mile or so and it did it again but not as bad i can feel it coming on and just back off on the pedal shift to 2nd and it did'nt keep doin it so i'm still kinda miffed at whats up here

[catmandoo]

oh by the way go to napa and check the price of a rebuilt pump they told me over 1000.00 i about s##t my pants good thing i know a good rebuilder.

[britannic]

If the symptoms were reduced after replacing the electric lift pump, try this: get a another fuel cap and fit with a Schraeder valve (the same as a tire valve), pressurize the fuel tank to 7 psi and check for leaks in the fuel and return lines.

Air leaks can cause violent surges, but they can be very hard to find as they only occur under vacuum, hence the pressure test. This step might save you some bucks on a new inj. pump if it fixes the problem.

[ 07-31-2003, 08:03 AM: Message edited by: britannic ]

[G. Gearloose]

That price was likely before the core charge credit. There are other sources anyway.

[catmandoo]

i was there for a radiator and had to kill some time so had him check and he didn't mention core but probably the reason they want so much.

[catmandoo]

well put 420 miles on it today and it only did it 3 times what i would call really bad but nothing like it was it still has added acceleration but nothing like before and say i come to a corner and don't have to stop i'll downshift to 2nd and take off and when it gets about 30 or so about the time it does it it seems like it wants to surge but just doesn't kinda weird feeling other than that still pullin 26+mpg talked to the guy i got it from and he always used power service which i have'nt wheter that has an effect i don't know may have to start.has anybody used the new soydiesel?if so do you like it . the station i get my fuel from went to it for farm delivery but hasn't put it in the pumps yet.

[britannic]

It sounds like an intermittent air leak possibly in the fuel return lines or faulty HPCA valve (glass bead in nozzle on top of inj. pump).

[catmandoo]

i kinda forgot about those little glass balls in there i'll have to chck that anyway friday i put another 250 on it and it did it real good 3 times but still nothing like before but now it kinda has a ,i really don't know how to describe it little surgeing as you drive kinda like it's running on 8 cyls then occasionally all 6 but it doesn't miss kinda wierd feeling if it was a gas i would suspect bad plugwire or 2.it doesn't have to be under load either.when it does this and this morning when i started it it kinda had a lopping to it when it idled, up and down but not much of an rpm change maybe 50 to 100 rpms.

[britannic]

Those symptoms you just described can also be consistent with an air leak in both fuel feed and return circuits or an HPCA malfunction.

Air being drawn into the fuel feed line can temporarily disable random injectors (until the air is purged) and vary timing as the pressure in the return circuit fluctuates (this is how the HPCA works; the check valve is forced off its seat, which lowers the fuel return circuit pressure and advances the timing by around 6 degrees).

This recently happened to me, when my fuel filter housing started aspirating air and I had a few (but not all) of the symptoms you have described.

[catmandoo]

well a little update yesterday i took the return fitting off the front of the pump and there is just a little valve in there i was expecting the glass ball, anyway i first took off the barbed fitting and down in the hole by the valve was a little piece of red silicone,whether it fell off when i took the first fitting off i don't know but anyway blew it out and decided to change the filter and since then it's been running great no surge and it even sounds different now i only drove it about 20 miles so i'll see how it acts tomorrow with about 300 on it.

[britannic]

Excellent news, glad we were able to help!

[catmandoo]

well only got about 200 miles today and so far so good no surge but yet in 1st just before i shift it still has a little feeling like it wants to surge but just won't other than that she's good to go.

[catmandoo]

well put on 400 mi;es today and its back but i did notice that it seems to be when i drive at 65 or over that it bothers say drivin down the interstate for 30 mins or so and come to off ramp let coast to stop and take off and it surges before i can hit 2nd otherwise at say 55 it doesn't bother.

[britannic]

The CDR can also cause the symptom you just described. Since you found debris in the HPCA valve, it may be a good idea to check through the system again to see if there's any more in there.