I have a '95 6.5td. It has recently started missing and stumbling, mostly under hard acceleration. Freeway on-ramps tend to trigger this problem. The truck never stalls out, and if you back out of the accelerator, it will run normally again. My PMD failed about 5000 miles ago, and I replaced it with a Heath cooler, so I hope this is not the problem again.

It seems like it is being starved for fuel. I am going to do some troubleshooting this weekend. The first thing I will do is change the fuel filter and put a fuel pressure gauge on the filter drain line to verify the lift pump is working. Is there anything else to pay attention to? I've also read about an oil pressure switch that fails--I think this has something to do with the lift pump? Any hints or pointers would be appericiated. Thanks!

Please let me know if you ever figure this out. Every 6.5 TD I have ever driven does this, and I am not exactly sure what causes it.

You can determine whether or not the lift pump is working simply by opening the petcock on the the thermostat housing (valve that drains the fuel filter bowl) while the engine is idling. If engine dies, your lift pump or OPS isn't working.

Mine was doing that and occasionally throwing a code 31. It turned out to be the EGR supply solenoid. But, check the lift pump for sure too.

Mine doesn't cut out under hard acceleration. I relayed the LP load switched by the OPS. The OPS is sapposed to be rated at 1 amp and the LP draws 4 amps. Under a hard acceleration it can become intermittent.

Please let me know if you ever figure this out. Every 6.5 TD I have ever driven does this, and I am not exactly sure what causes it.Mine did this too until I wired the lift pump to run without the OPS. It runs so sweet now. I used a add-a-circuit to do this.

pull the harness loose from the lift pump and check for voltage when cranking and running. if you have juice during both the relay and ops are fine and you need a lift pump. i just today installed the third lift pump since i got the truck (last one was in 2000) if you have juice when cranking but none running the ops has crapped out. if no juice at any time its time to start checking fuses and relays.

I had the same problem with my 6.5 1999 chev 1 ton found the waste gate was stuck on tubro in the close position. Freed up wg, problem went away. Had more power entering freeway on ramp.

pull the harness loose from the lift pump and check for voltage when cranking and running. if you have juice during both the relay and ops are fine and you need a lift pump. i just today installed the third lift pump since i got the truck (last one was in 2000) if you have juice when cranking but none running the ops has crapped out. if no juice at any time its time to start checking fuses and relays.Oh course you might still have a bad OPS. They seem to work at times then stop working while going down the road. It cost me 15.00 bucks and could be used as a test for a few days to see if anything else changes. Or you could just change the OPS. HoweE also show another way to use a relay and bypass the OPS, your will have to search his profile and look at the pictures on his website.

Thanks for the help everyone. I had a bad oil pressure switch. I replaced it and it runs great now.

That is good news Mike, we like to hear solutions as well as problems from time to time, do us a favor and update your signature so you don't have to repeat nor do we have to try to remember your configuration every time you post.

I push this as it also helps to trouble shoot problems knowing what you have on the truck, there is a thread in FAQs that links to Howie Es site on how to drive the LP with a relay controlled by OPS, OPS contacts hard pressed to carry LP load, pitted or dirty causes problems you encountered even though oil pressure was still being indiicated properly.