Anyone ever heard of one of these 6.5's high revving as soon as you start it? The truck is a 1994 Chevy 2500, with about 140,000. The PMD is an updated number but in the stock location. At first i thought it could have been the APP but after some testing and unplugging it while it was runnin with no change i canceled that out. My only guess is that it could be the IP. It used to surge / high rev intermittantly when you would drive it, noticed some water in the tank. I replaced the tank, changed filter and lift pump and now can see good diesel being pumped into it, and the problem just keeps getting worse. It being an OBD I i came up with some codes, like a code 13, 18, 32, 35 and 54. Vacuum tested the EGR and it holds steady.

I now have the IP off for inspection, anything else i should be considering while i have this thing apart? Never heard of these things red-lining as soon as the key is turned.

you need a new injection pump. the armature inside the pump is either bent or broken causing the run away condition you are having.

Yep it's the armature. Not bent though. More than likely the screw is broke off the end. Recommend new pump. PM me if you need help.

wouldn't a bad potentiometer in the accelerator pedal do the same thing?

I don't think so. There is actuall 3 reostats in the app. The psm checks them against each other. If they don't jive the check throttle light on the cluster will come on and it will set a code. Kind of a safety. If one crapps out it will still run with the other 2.

Mine did that on a 95, the FSD was fried, literly melting, put in spare and ran good again.

Adrian.

OK, my working knowledge of the rheostats was not up to par.... Good info to have on the redundancy of the system to check for that kind of failure. I was always worried about any kind of fly by wire.

what about pmd module. my 94 did the same thing and swapped pmds then ran fine.

Thanks for your guys' input. I have the IP being tested as we speak at some diesel injection shop up here in seattle. As far as the throttle position (APP) as its called on pedal, i was able to run all 12 electrical tests on it and it passed 11 of em. I was hoping that was the problem but now im hoping i have a bad pmd. I'll keep ya updated as soon as i figure this bad boy out....

Seen a few PMDs do that. One was a new Dipaco out of the box. Truck ran wide open.