Hey everyone, I have a 1995 Chevy K2500 6.5 T/D. It recently has had the same stall issues that everyone else has. So the first thing I do is replace the PMD for the 3rd time in 3 years. Still the issue exists, so I ask around and my buddy tells me that it is my OPS not allowing my lift pump to work. So I change the OPS and not only will it not shift out of 2nd gear, it wont turn off once I turn the ignition off. So I tell my buddy and he says Oh.. that sounds like an ignition switch problem. So guess what, I replaced that and it still wont shut off until I pull the PMD relay. So I would appreciate any ideas, because I am lost here. I didn't think I would have an issue getting it to turn off since its been a mother to just get it to stay on. Thanks beforehand!

 

There is no PMD relay so I don't know what you are pulling?

Good chance that there is a short to power somewhere in your harness that is keeping the ECM powered up?

Any other wiring get altered lately?

You should also google "OPS relay mod" and install for long term reliability and AC Delco ONLY for OPS or other switches and sensors on these trucks.

 

No other modifications to the electrical system. I have to disconnect the plug that goes into the PMD to shut the truck off. I seen a similar post to mine but there was no solution posted so it does me no good. I was thinking it was a loose ground but I haven't found it yet! any other info would be helpful

 

It won't be a ground problem in my opinion-it will be a hot wire chaffed through to another power wire somewhere between the key or fusebox and the ECM likely.

Your guess is as good as mine though where it is-you could try pulling fuses to see what shuts down the engine and trace from there?

 

Hahaha sounds like im on a mission here. Well thanks and if you think of anything else let me know.

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Racer I think you're right. I started the truck this morning and like before it wouldn't shut off after I turned the ignition off so I started pulling fuses and when I pulled the ecm b fuse it shut off right then. Also my glow plug light barely comes on when I turn the key. Its like they are already hot or the relay is not working how it should. Sound like any problem you have heard of?

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Do you think that its possible the previous owner bypassed the ops and when I installed the new one it created this issue or is that impossible?

 

Glow plug light barely on is bad ground somewhere.

ECM B should kill the engine since it's ECM battery supply.

Finding out whay power doesn't get removed with the key off is next0-I would still lean towards bad ignition switch even if it is new-since it's a multi contact switch it could be failed in the on position?

Since the problem started with the new OPS I would check wiring there to see if someone tried powering the LP directly from the ignition and simply scotch locked a power wire to the grey LP wire-if so the OPS would send power back the other way as long as the engine ran.

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Seems we are on the same page at the same time.

 

How about I decided since my problems started when I changed the ops that I would just take it out and see if it would start and run without it and guess what it does. Not only did it start up, it turned off with the key and it shifted out of 2nd gear. the only flaw is the oil pressure gauge doesn't work. So im guessing the ops was bypassed and that is what is causing my electrical problems. do you think I should find the bypass and fix it or would it be fine to leave as is?

 

I would fix it,because it's a safety issue.

If you ever get in a wreck and are unconsious a ruptured fuel line would continue to spill fuel till the key was off and people could get BBQ'd.

Google OPS realy mod and install that for long term reliability.

 

this is very similar to what im dealing with after replacing ops in my truck today, we started truck up, went to shut it down, and it wouldn't shut off, the lights and all shut off, but had to pull the connector from pcm, I replaced ingnition switch, and now starts and runs fine, and shuts of ok, just somewhere lost (P). ran out of daylight, will let ya know what we find.

 

I think it would be cheaper too find a new buddy