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

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

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

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

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.

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.

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

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~!

Had swwn something on this before, I think it turned out to be the solenoid for waste gate.


Good Luck.

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. http://www.dieselplace.com/forum/smileys/Cool.gif


towner7

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`

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.

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.

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.

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

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.

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

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

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.

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.

I have the GM shop manuals for 1996. They woud be costly. GM treats each system, IE oil pressure switch, as a seperate drawing. This makes it simple to work through a given system but makes it very difficult to see any interactions.


Sorry but I have never used Hemmings or Chilton but if you go to your library they often have these. Realy look at the wiring drawings and be sure they make sence to you before you deside to buy.

Quantum,


Try looking at a copy of Haynes, their repair procedures generally are lacking but in other vehicles I've owned the electrical schematics are pretty good, Auto zone carries them and they usually let you look at them before buying to see if they fit your needs.


I would recommend though if you plan on keeping the truck you invest in a set of the GM manuals, either new from www.helminc.com (http://www.helminc.com) or maybe pick up a set on ebay or some of the vintage book sellers on the net do a google search for vintage books/booksellers I've found a lot of used but good manuals that way.


BTW another vendor of a cool plate and PMD remote mount is www.heathdiesel.com (http://www.heathdiesel.com) it remote mounts pretty much where you want out of engine compt. recommended location is as Howie says above. Bill Heath is very knowledgeable on GMC, & willing to share tips. He claims a near zero fail rate with his PMD kit.


Edited by: Turbine Doc

BTW another vendor of a cool plate and PMD remote mount is www.heathdiesel.com (http://www.heathdiesel.com) it remote mounts pretty much where you want out of engine compt. recommended location is as Howie says above. Bill Heath is very knowledgeable on GMC, & willing to share tips. He claims a near zero fail rate with his PMD kit





That's where I got mine.


I'll tell you, what a great guy he is (had never heard of Heath Deisel before), he just happened to be in his office Sunday ( I called just to see what their hours were) and talked to him for at least 20/30 minutes. Bought it and he's sending it first thing this morning after working out how it would be sent across the border by USPS, should hopefully be here by Friday.


Would buy from him again in a second, great design and really goes out of his way.

Near zero, 1 failure in 10 years sounds pretty good to me, I called Bill and asked directly what happened, I'd recommend to anybody call him, he will tell the straight story even if it doesn't result in a sale.


A bad driver manufacturing defect beyond his control was the cause. He also said if you wanted to you could submerge his driver, but did not see why anyone would want to. His prototype has been in service on 2 different trucks and still going after 10 years.

As far as wiring length if you wanted to; you could mount the PMD in China if you sized(gauge) the wire properly (okay maybe China is a strech); but the lengths in our truck the line drop loss to the driver is inconsequential. My concerrn was EMI from the length, and it being an antenna for electrical "noise" and maybe it needing twisted shielded pairs, Bill did say they had done a custom kit for a motor coach; PMD up front, and engine in the rear without problems.


I don't know how long he has listed that particular product at TDP I don't think it matters, I've always had pleasant dealings with him, never has he replied to any of my querries with a condesending attitude, nor has he trashed anothers product, he has even directed me to others who may build better mousetrap if he doesn't offer one.


A solid vendor you can trust, I dare say if Bill says his product is reliable, it is and if not he will make good by it.Edited by: Turbine Doc

Quantum,


In later models OBD II, the PCM energizes the lift pump circuit 96+ IIRC, the OPS acts as a back up to this and energizes lift pump relay in conjunction with PCM command.


In the early models as Howie & Gm Diesel detail the OPS controls power to the lift pump, it is a dual purpose switch giving both pressure indication and pump power.


It has some weak contacts on the power side that aren't good at carrying power to the pump over the long haul, many have modded their trucks to have the OPS control a HD relay to provide lift pump power. I'll go through some reprint stuff to see if I can find it if you are interested in the details.

Obviously a sensitive subject with you I'll not argue about it; lets agree to disagree and move on. My experience with Heath Diesel has been a pleasant one. A good day to you sir.

GmDieselTech


What is this PDC you are defending so strongly? Lets have an address were we can have a look.


As for the comment the PMD is not waterproof or the connector are not leak proof how do you account for the fact that they both servive in the engine compartment through all types of weather, engine washing, and steam cleaning.


Please supply me with any drawing that would suggest the oil pressure switch has any capicity to influance a guage. My drawing shows it as a single normaly open switch with no evidence of a transducer.


Edited by: HowieE

Hmmmmmmmmm,


Should I chime in too?????????http://www.dieselplace.com/forum/smileys/Ermm.gif


Whatcha think TURBINEDOC???????http://www.dieselplace.com/forum/smileys/Cool.gif


Naaaaaaaaa, ain't worth my time!!!!!!!! http://www.dieselplace.com/forum/smileys/Clown.gif


Tom

Oh BTW, he has had more than one PMD failure... http://www.dieselplace.com/forum/smileys/Stern Smile.gif, like I said I have tried them ALL so don't ya try to pull the wool over my eyes,.http://www.dieselplace.com/forum/smileys/Angry.gif I had 2 cook on a health unit and a member of my message board mentioned another and it was NOT a Stanadyne defect.
http://www.dieselplace.com/forum/smileys/Cry.gif


I can't believe what you've posted. Where in the world do you get and what proof do you have that he has "more than one fail" as you say ??


You know reading your reply's and having you pm me, I'm glad I bought Bill Heath's product.


If you want to push your product that's fine but bashing everyone else's, and I mean everyone, isn't the way to do it and certainly not a company I would want to deal with.

Sorry guys, GmDieselTech is no longer with us. PM me if you would like to know why.

Hey Guys,


Thanks for all the leads. I wanted to mention that the first pmd failure I had was on a '96. The thermastat was leaking on the IP, the pmd had that hazy white look you get from coolant leaks. I'd say it was the steam. (I wash my engine, on my truck, about every 2 months, never had a problem)


Currently, I found this excellent aluminum bar that i intend to cut to size, drill and tap, and mount the driver on. I say excellent because it was extruded with natural cooling fins, no billet needed. I guess I'll buy the wiring harness, to get it away from the hot engine area.


howie, my gut feeling is that the OP switch does feed the dash. I replaced mine 3 days back and the read on the guage is different low and high. This says to me that the new switch is reading pressure different. since i changed little else, this seems plausable.

Oil press circuit.


Howie you are correct in the single wire from OPS, spent some time in the manual to make better sense of it . I think though the circuit is different between how OBD 1 & 2 handle OPS in regard to fuel powering, in my 98 manual you have to go to 2 sections to maybe make some sense of it. I had to go to vol 1 for body and acessories for the pin out diagram, and vol 3 for fuel controls diagram.


Looking at the OPS connector there is capability for (4) pins only (1) is used pin A (tan), the oil pressure is registered at the gauge via a 0-80 ohm resisitive output, to test if bad GM says put their J tool on it and vary resistance to track displayed pressure 0 ohm is low, and 80 is high. No number as what ohm = what psi I assume 0-80 full scale and 40 ohm would be mid scale.


Now on OBD 2 I assume somewhere the PCM is also monitoring the output of OPS current for the backup command to energize and deenergize lift pump.


Lift pump control description from manual paraphrased; Key on PCM energizes fuel pump relay, lift pump remains on during glow cycle. If engine not started immediately after glow cycle, PCM shuts off lift pump until engine rpm greater than zero. As a back up , the lift pump can also be turned on by the OPS. When pressure reaches 4 psi & the fuel pump relay does not complete the circuit, the OPS will close and complete the circuit to run the lift pump. This is where I get fuzzy as I can't in my minds eye or from the schematics, see how a resistive device can power the lift pump, so my assumption here is the PCM does the switching on or off either via rpm signal or OPS signal.


In my DP reprint book for 99 it shows a schematic with a OPS using 3 pins (1) 12v supply, (1) to gage, and a 3rd to lift pump (the gray wire) which is where they connected the relay control leg, so I think 2 paths in that OPS 1 instrument and 1 control, & its the control contacts that were failing in the earlier models needing auxillary power for long term fix.


Unfortunately I don't have a OBD 1 manual to confirm my theory, but from what I read between the lines and posts Iv'e read over at DP if I don't have it exactly Im pretty close to how it works. Anybody else know more please add input, I'm here to learn myself.


I copied this into a new thread so somebody could search and find easier later if you have more how OPS works info send there please.


Edited by: Turbine Doc

Well like every thing GM does there is a mistake in thier manual.


Yes the oil pressure switch has 2 functions built into it. I have discribed the switch section that supplies power to the lift pump while the engine is running. There is also a resistor, the tan wire, to ground that gives the guage reading. These are 2 completely independent functions that just happen to be enclosed in the same housing. Either one could fail and have no effect on the other function. One function is discribed under engine controls, the oil pressure switch, and one is discribed under instrument cluster, the oil pressure guage.


As for the mistake in the manual. GM has drawn the tan wire as going up to the temperature guage and not the oil guage. They also have the engine temperature sending unit going to "Nowhere".


Not sure what the original question was, but if there is still a question please restate it and we'll try again.

If the truck just shuts off like you turned the key off with no RPM drop off then I would look at the PMD. If the RPM's slowly drop off then stalls it's running out of fuel. It might now have a really long crank then stall again shortly. It's still a fuel delivery issue.


After the truck starts open the "T" valve at the thermostat housing, this is the water drain circut. If nothing comes out the lift pump is dead. Close the valve quickly because it will stall and be tough to start.


I just went through a similiar stall issue as this and my lift pump was making plenty of noise but not letting enough fuel through it. After R/R lift pump and OP switch no more issues!


Summer fuel in a winter cold snap will due the same thing for fuel delivery.