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Discussion Starter #1
Have read all over about the stalling problems, I wonder if anyone has any suggestions and if I'm looking at this correctly, this seems to be the best site around.


1995 Chev Reg Cab 4X4 Pickup, 205,000 km.


Started stalling about a week ago, would do it on the highway after about 15 km, would also stall just going down the street after a few minutes after truck has been parked about an hour. Check engine light doesn't flash so no codes.


Changed the fuel filter.


Now, it has not stalled as often after putting in the fuel filter, but still does.


A couple of times it wouldn't start (shook some wires under the A/C and banged where the lift pump is and it starts, still it sometimes stalls after going a few blocks, then starts, stalls again, then starts and is fine for the rest of the day. ALSO when it starts to stall on the highway (engine light goes on, no power) I press the accelerator once or twice and it has kicked back in. (sometimes feel a bit of a miss or buck a few minutes before that)


Now when I put the fuel filter in, had a heck of a time starting it til I called GM and the guy gave me a hint how to get it going (fill the filter chamber, inject a bit of air in the gas tank and it started) but he did say my Lift Pump is probably gone as it stalled when I opened the valve to remove the water and it would not prime when I tried to restart it.


I have read alot about the PMD going bad but usually after the first stall or two it runs fine the rest of the day.


Now I want to change the Lift Pump but I have also read that it could be the Oil Switch that is located near the Lift Pump.


So...


Could the switch and/or the Lift Pump be causing the stalling ? Should I change both and is there a way to test the switch and where is the switch located.


I really like the truck but it's certainly unnerving reading all the problems these are having ant the GM techs that can't figure it out.


Thanks in advance for any help or suggestions, it's VERY much appreciated.Edited by: 95 Diesel
 

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the 95 models are notorious for failling ignition switches.


when it stalls, do any of the warning lights come on? dont just assume they do, look for the lights when it stalls, if the check engine light does not come on as the engine dies, and stay on.....prolly bad ign switch.


mine did that about 2 years ago, then other symptoms developed, like defaulting to second gear.


good luck
 

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Discussion Starter #3
Hi Pat,


First thing that comes on is the engine light (kind of a picture of the engine) then if I press on the gas it sometimes kicks in again, if not then all the lights go off when the engine dies.


Can you test the lift pump without it running ? Tried it today and really didn't feel anything just felt like the vibration from the engine, guess I'll have to check the oil switch then see about the lift pump, just don't want to spend $300 + if it's just the switch.


Edited by: 95 Diesel
 

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Park the truck in a very quiet spot. Roll down the window, put the gear selector in D and turn on ignition to start you should hear a ticking sound. Also, it will tick at sut down if lift pump works until oil pressure falls off. If you have no starting problems it may not be the lift pump but sounds like the infamous PMD/FDSS failing problem, but check lift pump about $80 US and OPS and igniton first.Edited by: 16gaSxS
 

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Discussion Starter #5
Thanks, tried that and heard nothing.


Will have to put in a new one then if it doesn't work guess I need the Oil Sending Switch. Truck only stalled once today when I had just started it up after stopping somewhere for 5 minutes. Since I changed the fuel filter it's been much better, but hope I can find the problem, hate driving it like that.



Thanks for the help, will keep you posted on my progress.
 

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sound like a lift pump and maybe the fuel control module.
or the black box you can check the lift pump by opening the fuel bleeder on top of the filter turn the key on fuel should come out. usually the lift pump will caues a hard start. a stall after driving souns more like the
control module.
 

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I Know it's hard to spend $300 on a new pmd/fsd , but it's worth it to buy one. I just went through the same problems. Every fix seemed to make the stalling go away, but a day or two later it stalls again. The problem didn't stop untill I replaced the pmd/fsd. Since one of my earlier fixes was relocating the fsd to an fsd cooler it was a snap, but the relocation was a trial. When I removed the intake manifold I took the time to port and polish the intake runners and reseal the lower intake gasket properly. The key to the pmd/fsd is no check engine light will flash and no codes will be given to clue you in.


test the fuse for the lift pump(above engine on fire wall)and the circuit for power, if you have power, you need a new lift pump. if it's the circuit look to ignition switch ,or oil switch.


quantum mechanic


Edited by: quantum mechanic
 

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After reading your opening lines, I felt complied to add this:I'm sitting here with a 95 Suburban 2500 4x4, with a brand new 6.5 turbocharged engine that, has slightly over 10k miles. Extremely careful on the break in period, Amsoil dual filter installed after 1k miles, oil, oil filter changed, fuel filter, new glow plugs, etc. In the last month, it has started to smoke alot when first starting up (I mean alot~!) but, the thing that gets me is the way it acting up..While driving down the road, acts as if it not getting fuel. WHat with the buckling, then clears up. Well, over the weekend, it actually got to the point where it had no power to move..No matter how much I push on the pedal, it went down to a complete stop. Then stalled, tried restarting, that was okay but no rpm indications..therefor, I couldn't drive or move the vehicle. Lucky me(?) it was in front of my house when this happened..Later I went out and, started it right up then moved it off the road next to my house. Several days later, I started it up and, drove it to the dealer for repairs,(Since it's covered by warranty)


Has anyone a clue? If I find out what's going on, I'll post it here but...Sure would like some inputs~!
 

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95 Diesel


Thanks for your reply and "tip"..After doing the search, I found the thread on the wastegate problem and, that made more sense than anything else. I figured it to be something so simple, yet vital to the " fuel/air mixture ratio" as to cause something similar to this. I'll be sure to post what the tech at the dealership finds.



towner7
 

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Follow up:


Beware~! Not all fuel is suitable for winter useage~


The word finally came in from the tech. It was a combination of several problems. 1st problem was the o/p switch for the the lifter pump. 2nd problem was the fuel..It seems that the local Mobil station that I've always bought fuel from was selling warm weather fuel. Test on fuel was reading 30 vice 39-44, which is the cold weather fuel rating~Just to say also, I have been using a fuel additive to prevent jelling but, that didn't help me in this case. I'll be talking to the owner of the station, to see what can be done about the expenses this has cost me.


That's it in a nutshell..


Thanks for your inputs`





 

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Discussion Starter #12
Well....


Finally got the Lift Pump put in Friday and it works fine (certainly noisy) Worked great yesterday and this morning, drove for about and hour to go look at something and when I went to restart the truck about 20 minutes later, turned the key and it wouldn't go, waited a minute, tried again and it started after turning it over for about 10 seconds instead of the usual 5. Went a few other places and the one time I started it, it worked fine, after 30 minutes on the road just before I got home it stalled at about 40mph, stopped and it started right back up.


It REALLY feels like fuel is not getting to it as I try and start and it doesn't start the first time the second time if I crank it longer it usually starts. If it was the PMD that was the problem, wouldn't it not start the second time ?


-Also on top of the motor there are about 6 bolts holding the cover down (not the plastic DIESEL thing) and the bolt nearest the Fuel Filter it looks like oil is coming out, can I just tighten that or are the tightened to a certian pound ?


-Could there be anything else, think it's the PMD ??


-If yes, where can you buy those remote coolers in Canada ?


-Does anyone know a good Diesel mechaninic east of Toronto by any chance??


Any suggestions would be welcomed.


Thanks very much.
 

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Your problem is classic PDM/FSD failure. The FSD is mounted on the IP and uses the IP as a heat sink. Over time, 30,000 to 50,000 miles, the electronics in the FSD degrade from heat. Trucks will most often stall after the engine is at operating temperature and the air flow over the IP is low like stop and go traffic. The fact that a truck will restart after a few minuits is a result of the IP cooling down in that time just enough for the FSD to work again.


I have had 2 FSD fail in 130,000 miles and have mounted the current one inside the front bumper to make sure it remains cool.


An observation after mounting the FSD in the bumper was the fact that the truck had notisablely more power in general. I have to beleave that even while the FSD was running what I considered normaly before stalling it was missing enough to account for this differance. When mine failed I was carring a spare and my site has pictures of the heroic installation to get home.
 

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Discussion Starter #14
Ok, here are the codes I pulled (checked twice)

In order...

29 (flashed it 3 times)
35 (flashed it 3 times)
36 (flashes it 3 times)

Truck died like 8 times at the beginning of the night, filled it up (was 3/4 full) and ran perfect the rest of the night)

Taking it to a plow place to get the wiring checked, had a short in the plow lights, guy did a lousy job so have to take it somewhere else (toggle switch for the plow lights is pretty hot).

Hazard switch was gone so had to change the whole indicator (sheesh) but still making clicking noises even when it isn't on.

Also dash lights wnt out last night, will get it checked tomorrow.
 
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The PMD (pump mounted driver) aka FSD (fuel solenoid driver)often fails will NO codes, but when it does the 35 and 36 refer to the injection pump system = PMD.

Check battery terminal and ground conections.

Edited by: hoot
 

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Discussion Starter #16
Just an update of what's been happening....


1995 Chev with 7 1/2' Fisher Snowplow.
Regular Cab Pickup 4X4
6.5 Litre Diesel
212,000 Km (Appx. 132,000 miles)


A little history.....
Started stalling about two weeks ago, last week alot more often. Changed the Fuel Filter (don't know if it had been changed before, bought it at 123,000 (appx. 76,000 miles)
Changed the Lift Pump (was not working as I can easily hear it in the cab now)


Got the lights (plow and truck) redone as there was a short or something that knocked out the indicators, the Hazard switch was not working properly, had to replace the whole turn signal assembly (great idea GM). First electrical guy did a brutal job, changed the signal assembly (coating was melted off the wires to the assembly), cut one of the plow light plugs (he knew I needed them), everything worked except the High Beams and said "I didn't touch them" and told me to get my mech to put the plug on (I was not impressed ).


Took it to a plow place, whole new harness, re did all the wiring (said there were no wires going to the hi beams), grounded it all right to the battery, the guy did a great job.
There was also 2 wires coming out from that large bundle behind the fuel filter, one was attached to the block, the other corroded off. Told it was a ground (black w/ white stripe), could not find where it broke off so grounded it too the same bolt on the block. Disconnected the batteries for a minute.


Now the Stalling...
-Drove home last night (20 minutes, half hour maybe) stalled once, restarted.
-Went plowing this morning, first job (running time maybe 1/2 hour), stalled, restarted.
-Drove to next job (20 minutes maybe) parked the truck, shovelling sidewalks, truck stalled. Finished shovelling, truck started up.
-Stalled 1 minute later, would not start, shovelled some more, started up (turned key longer than usual)


This is where I'm wondering if it's the PMD....
-Went to another job (10/15 minutes away) cleaned the driveway, parked the truck (bit of an incline, nose up) shovelled the sidewalks, truck stalled), would not restart.
Tried again, nothing. Put snow on the PMD, 3 more times, no start.
-Put truck in neutral, rolled down the driveway to an area more level, truck still would not start 3 times (more snow on PMD, nothing)
-Then, getting desperate, turned the key on (not to start), turned to off, turned back on to start, truck started.
-About 500 ft. down the road it stalled, took my foot off the pedal then back on once or twice, motor kicked back in (has done this before).
-Drove to the next job, turned truck off, started fine. Ran for maybe hour and a half, stalled once in a driveway and started back up (again turning the key a little longer than usual).


Sometimes it starts right back up, sometimes starts and stalls a minute later, sometimes have to give it a few minutes, sometimes runs longer and sometimes have to turn the key on longer.


Still looking but seems more like the PMD, it must send a signal for fuel. I hope anyway.
 

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sounds like the pmd and every pmd problem I've read of. this problem is epidemic among 6.5 owners. The pmd is available at any gm parts dealer, as well as many aftermarket suppliers. I called around and realized gm was asking 300 or so ( at the low end) But when I showed up to buy it a weeks worth of frustration poured out on the gm parts counter. The parts guy upon hearing my litany of sorrow about the fuel solenoid driver, knocked a hundred off the price and I got it for 200+ with tax. I had preveously installed the fsd cooler($100), but a handy guy should be able to make his own, as I don't plan to buy another for my other 6.5. Also you mentioned oil leaking out of the area where the upper intake bolts down. It could mean a $10 gasket and there is no reason why you couldn't replace all of this yourself(including pmd).the pmd is tricky to remove. I couldn't find the right torx w/ an offset so I cut slots into an allen wrench that was close enough. luck


'93 GMC 6.5


'94chevy6.5


'96chevy6.5Edited by: quantum mechanic
 

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No Gm tech,


I didn't experience a failure since installing the fsd cooler. Just the realization that for a C note, it's worth it to make your own vs.still mounted to the pump.


I do see the logic in the remote wiring relocator.


can you tell me why an oil pressure switch failure keeps the lift pump from working on the 6.5L ?Edited by: quantum mechanic
 

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If you look at the wireing drawing for the oil pressure switch you will see that it is the oil pressure switch that feeds voltage to the lift pump. The purpose of this oil pressure switch is a safty to cut off fuel flow if the engine stops in an accident, it is not the pressure switch that feeds the oil pressure guage.
 

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Howie,


Can you recommend a good service book for 6.5's I have Chilton's and it lacks information. it doesn't show the relation between the lift pump and the O.P. switch.
 
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