TowRig.com - Diesel Discussion and Tow Tech

I am having a problem with my 1996 Chevy 3500 6.5 TD vin code "F". I am having an issue that no one around here can seem to figure out. Here are the facts. It is a runability problem. If you are running down the road, the engine acts like it has run out of fuel. It will sputter for a second or two and then pick right back up.

If the truck is idling, the RPM will surge, then sputter and cut off. This happened 4 times on Mar 19th. It didn't do it again until June. It has been in and out of the shop trying to figure it out since then. Now if the truck sits for a week it may take 50 or so miles before it starts. I picked it up from the shop again yesterday and it ran like a charm all night. I drove it about 50 miles. No probems.

I get in it this morning to drive to work, I go about 10 miles and it starts acting up again. It acted up about 10 times in 2 miles. It was 98 degrees yesterday when it drove fine, it was nice and cool this morning when it acted up. Outside temp seems to make no difference. I have changed the fuel filter twice in 5K miles. That doesn't help. I have tried with and near empty fuel tank, a full fuel tank and everywhere in between, all make no difference. The injection pump is only 13k miles old.

The only 2 codes it has set in the computer was a fuel shut off solenoid and the lift pump both for low voltage. Both have been changed , so it no longer sets a code in the computer. Air filter is clean. No leaks on the engine. The only thing the local diesel shop says is to change the PMD, but in the same breath they say it is only an educated guess. as the truck does not show any normal symtoms of a failing PMD. The truck starts very easily in the mornings. Sometimes when it surges while driving it will cut all the way off. If you shift the transmission into neutral it will start right back up without hesitation.

When the truck is running it runs great, when it acts up, it will drive you crazy.I cannot think of anything I haven't tried yet. The local shop here says change the PMD, at a cost of $ 725 for the heat sink, mounting remotely, everything included. But then they say in the same breath that the PMD is an educated guess. The other two items were also educated guesses. I want to fix the truck not keep swapping parts until it fixes it. I have a problem with that kind of money for an "educated guess". Can anyone help? I have the 6.5 TD vin code F. 3" down pipe Kennedy 3.5 in exhaust sytem w/ no cat. A Kennedy (Wester's Garage) reflashed computer and AFE air filter and modified air box. A 4L80 Tranmission. I have just cancelled my family vacation because I can't trust the truck. Someone please help.

I don't know what to tell you. I've been told to check all the grounds. There are some on the back of the heads. Good luck.

Check your lift pump to make sure its operating. Your OPS may be shot, or only working intermittantly. If you dont know how to do this, ill give the short version. Open your hood and locate the little brass t-handle near the t-stat with two rubber hoses coming off of it. Grab the loose one and stick it in an empty bottle of some sort. Start the engine, and with the engine running open the t-handle. If a healthy stream of diesel comes out, close the valve as your pump is working. If one doesnt, and the engine shortly sputters and dies, your LP is not working, most likely due to your OPS being bad.

Changing the PMD is not a bad idea either way, as they dont always show the same symptoms. Some have reported some very, VERY odd problems that have been cured by changing a PMD. Also, that price is very high for a new pmd, you can very easily install a new one, remotely mounted yourself for much much cheaper. One tip if you go this route though, leave the old PMD on the pump. If the new pmd cures the problem, or even if it doesnt, you will have a spare partially working one already on the pump for when the new one fails.

If you were closer to me i would let you try my spare PMD to see if it cleared up your problem, to bad.

Have you posted your problem on the Diesel Place?

I have checked the lift pump, the old one worked fine but I changed it anyway. I will perform the test again on the new pump. I will also try the Diesel Place. If you here of anything that might help, let me know. I left the truck at home today, because it started acting up last night, again. It cut off 4 times just trying to back into my driveway. Again, it always starts right back up. It's driving me crazy. Thanks

The OPS was replaced when the last IP was installed 12K miles ago. I am not seeing any fluctuations in the oil pressure gauge.

Gage pressure reading has nothing to do with the OPS. I would also say the PMD, but that is an expensive guess. Try over at the Diesel Place. Look in the stickies at the top of the 6.5 forum for a diagnostic checklist. Run through that, and start a new thread with your results, and problem. There are several very smart guys that are regulars over there, and will help you resolve this problem. Good luck.

I have now ordered a new PMD from Heath. I can only pray that this fixes it.

WELL. Did it fix it??

It has been a week now (300 miles) and the truck has not skipped a beat. My hat's off to everyone who helped with the issue. Also a huge Thank You to Bill at Heath Diesel for his help as well.

Right on. Glad to hear it. Bill has answered a lot of my questions. Really nice guy.

It has now been over 1500 miles and I haven't been happier. Thanks everybody!!!

It hase now been 3000 miles with no problems. Thanks to Bill Heath and all you guys. I love this site!!!!