PDA

View Full Version : Help Diesel Motorheads!



Hunter
09-26-2005, 08:50 PM
I have a 94 Chevy 1/2 ton diesel PU that's started to misbehave.

It's started to stall...abruptly, as if I'd turned off the ignition key. I took it to the dealership that had installed a replacement pump on it 2 years ago and, as it was just out of warrantee, Chevy agreed to cover half the costs. Unlike last time, when it'd start but not make power regardless of the throttle position, this time it starts fine but just stalls - usually at a low rpm. Once in a while it hickups at speed (often 45-55 but that's posted speed limits on the way to work) but relights immediately - as if I'd turned the key off and then right back on. A couple of times, it would require a few burst of cranking but would relight with a lovely cloud of smoke. Generally, it runs great and naturally it ran fine for the dealership's mechanic - not a hiccup.

The dealership says a couple things:

The fuel is of a low quality. He wouldn't tell me what it should be or exactly what it was but said "low quality" and with that I read likely old/low energy available. He did indicate it was clean and free of water; the reason I took it to the dealership was that I had just filled the tank and suspected that the fuel was contaminated (they were willing to drain/purge the fuel system if this was the problem) but this has been ruled out.

The computer didn't show any codes so the truck would appear to believe it's sound electronically.


Here's what I know:

This thing was built when sulfur was part of diesel. I've never used additives but went shopping. Lucas oil sells a product that they advertise to specifically combat the lack of lubricity of low sulfur oil. Gonna give that a try.

The service rep didn't know if they'd checked to see if there was air in the fuel return line but I'd be surprised if their was. The mechanic checked the filter and reinstalled it as it was clean. In fact, I'd replaced it a few months ago and I suppose that I might not have gotten the seal perfectly positioned. Hard to say, but it was idling in the bay when the mechanic and I were discussing this.

Pumps: it's on it's third and this one again has only 2 years on it and not a lot of mileage.

Beyond fuel additives, I'm drawing a blank but am not so excited about a 1200 dollar part being replaced needlessly. Any ideas?

MIJI

jkeiper
09-26-2005, 10:42 PM
It's likely the PMD (Pump Mounted Driver) The black box on the side of the pump. See if you can get one to plug onto the harness to try. They make a cooler that mounts it up on top of the intake to cool it better. Much easier than putting back on the pump.

Jim

JonesRacing#157
09-27-2005, 11:09 AM
I had a 94 also, the Pump mounted drive is my bet. I had 274k miles on the same pump but did have to replace the driver three time. also check the lift pump if the lift pump goes bad it will make the driver run hot and go bad. as for low power I would think maybe pump timing.contact John Kennedy at www.kennedydiesel.com he is the man when it come to a GM diesel

Rodney Nance
10-10-2005, 08:21 PM
With the first two posts. Same thing happened to mine (95)

AwesomeBullet
10-10-2005, 08:26 PM
Yep, that's the most common failure I have come across on those. Especially when it stalls like you shut the key off. Be sure to install the Driver Cooler with the new driver and you shouldn't have any more failures. None of my customers have. ;)

Sidewinder16
10-26-2005, 09:14 AM
Did you check your spark plugs??? If not maybe you should regap and clean them maybe replace them. LOL no but the pump mounted driver is also what happed to my old chevy.