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Shut off problems...Fuel pump problem maybe or PDM??

D

dieselman2

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Location
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Hello,
I'm new to the forum,I've done some reading around everyone here seems very knowledgeable about these 6.5 engines.
I have a 1995 GMC K3500,single wheel, regular cab 150,000miles. No engine mods it has had the Fuel Pump Drive Module (how O'Reilly's list it) (PDM)??with a heat synch. Roughly 2 weeks ago it gave starting problems & went dead just like you shut the fuel off,changed the fuel filter it was nearly completely stopped up. Now it starts with just the bump of a key as it always had. Now around 50-55 mph it will still just shut off just like you cut the fuel off, no surge or revving up to speak of,BUT it will start right back hot,cold it doesn't matter it starts right back. And you can drive it and it might shut off & it might not.
My mechanic & I aren't 100% convinced it's the Fuel Pump Drive Module (PDM??) because it will start right back with out needing to cool off when hot. Now I don't like how the fuel filter fits,it's all made in one piece instead of the drop in element AND then screw the retaining nut on. Its just a one piece & the box had got broke & the O-ring lost I put an on O-ring on it I had in my shop (I do hydraulics so its not a cheap hardware store O-ring) but I'm not sure its sealing off good,possibly leaking sucking air at operating speed & RPM. It doesn't leak at idle. I'm gonna change the fuel filter with the proper O-ring. Is there possibly another filter that could be changed or does this sound like a common Fuel Pump Drive Module problem (PDM??) Or possibly the fuel pump getting weak,the whole starting right back thing has me confused.
Any help or suggestions are greatly appreciated & I look forward to being contributing member of the forum.
Thanks

1995 GMC K3500 6.5 Turbo Diesel,automatic150,000 miles no engine mods other than Fuel Pump Drive Module relocation w/heat sync
1996 Ford F-350 CrewCab 7.3 PowerStroke 5-speed manual 313,000 no engine mods
 
First off welcome to TTS!

It could be the pmd as those are some of it's symptoms. It could also be fuel related. One thing you could do is get about 6" of clear tubing and put it on the IP return line and look for air bubbles. Lift pump could be weak as well as the oil pressure switch which supplies power to the LP.

I have also had the fuse for the fuel shut off sol (fsol) make intermittent contact and shut the engine down. Shine the fuse spades with fine sand paper.

Read through this:http://www.thetruckstop.us/forum/sh...t-Pumps-amp-OPS-operation-and-troubleshooting

And this:http://www.thetruckstop.us/forum/showthread.php?17457-Grounds-what-are-they-amp-where-are-they

And this:http://www.thetruckstop.us/forum/showthread.php?2647-Reference-Material-Lift-Pump-OPS

Here is an easy way to read your codes:http://www.thetruckstop.us/forum/showthread.php?589-6-5-Diesel-Technical-Library&p=111592#post111592
 
I think there is a small screen in the IP where the line goes in, it might be clogged, also a screen in the filter housing along with the filter, and the fuel tank sock could be stopped up.

Check those places, if the filter was clogged, the others might be also.
 
Howdy DM2 welcome to the site what part of MS you at? I'm down on the coast Gautier once we get over Issac give me a holler.

If you haven't had a chance to go throu it yet check out the TRL http://www.thetruckstop.us/forum/forumdisplay.php?218-6-2-and-6-5-Technical-Reference-Library

Check out the threads on grounds & fuel delivery, a poor gnd at back of pass side head intake manifold stud will cause intermittent shutdowns you describe as well as bad PMD, which becomes a FSD to us once it comes off the IP.

Where is your remote FSD mounted under hood ?

What type of heat sink is it mounted to a "home brew" or store bought one?

Do you know if the driver was new or used but good once mounted to the pump and relocated to a sink?

For the remote harness store bought or "home brew"?

If remote kit was "store bought" who's brand kit is it ?
 
Return the fuel filter and get one with the proper o-ring. The "New" design is easier to install then the 'unmarked' old filters that had a front and specific rotation to be installed. They also un-thread easier than the old nut design. The old design would drop the gasket from the rim and be junk.

Anyway Parts store is not my 1st choice for a PMD. Flight systems or the OEM stanadyne is the best choice. Dorman made in Communist China has a very well deserved bad reputation.

Clogged fuel filters can be from bugs in the fuel and require a biocide or dropping and cleaning the tank.

The fuel filter should be under pressure from the lift pump and leak at idle. If not at higher RPM it can go to a vacuum and suck air, but, not leak fuel.
 
Welcome DM2, any update?

I also say make Leo a mod (weather he likes it or not :hihi:)
 
No update as of yet. I hope to get to it over the weekend. These are all very good suggestions and all make sense.
I'm still leaning towards the fuel filter not sealing. But I've drove the truck a good bit today and it only shut off twice.
Something I noticed today,it makes a sound like a power steering pump low of fluid & the tachometer jumps around when it gives the shutoff problem.
If it doesn't make that sound & the tachometer doesn't jump around,it doesn't shut off.
Any suggestions to that? This is the first 6.5 I've owned so I don't know all their quirks. Up until its been a fine automobile & I'm amazed at the fuel mileage over 20 mpg
Once again thanks guys
 
Thanks for the reply to my latest observation Turbine Doc,but the truck isnt throwing any codes.
Its pretty much a crap shoot I guess youd say. Why i'm asking before I just go to buying the high dollar common parts,that mess up.
I'm convinced its something simple & I'm gonna try the suggestions i've been offered.
I appreciate everyones help/suggestions. They all make sense. If it wouldnt start right back I'd be convinced its the PDM
 
Gotta meet us in the middle DM2 we've repaired many of these 6.5s over the years, and most turn out to be simple but only so much we can do with partial information ergo why we developed the diagnostic sheet for you to fill out that gives us the basic info needed to make an effective stab at it/

Your description reads like PMD fail but could be gnds, PMD fails don't always give codes so if you would please copy/paste the diagnostic sheet swapping parts before eliminating the free to check stuff is an expensive way to go. Please answer the questions I asked about your drivers maker & location that will be most helpful. There is a method to our madness.
 
Tach going crazy has alternator issues written all over it and including grounds or loose/bad positive cables. Power to the alternator via the ignition switch is also suspect as well as fuses with corroded contacts and wiring. The positive battery cable on the driver's side is prone to corrosion from wicking up battery acid. The main power feed and charge wire is in that bundle to the positive bolt.
 
Different direction----You said whining sound and tach jumping, belt/alternator/idler bearing?? Tach is driven from alternator. If voltage also jumps radically the ECM may be shutting down---fuel solenoid would close killing engine. Soon as voltage stabilizes and you restart all OK till the next time. Can be erratic and unpredictable.
 
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