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Diesel wiring help needed


LawnSite Member
The truck is a 1988 GMC 3500 with the 6.2 diesel. When I bought the truck, the wire that plugs in up by the injector pump was just hanging there not connected, and another wire that I haven't traced yet was also not connected. The prior owner added his own wire- it hooks at one end to the injector pump where the original one did, it then runs into the cab and plugs into the distribution block right above the brake pedal.

Don't get me wrong, the truck runs fine like this, and if you disconnect either end of this wire, the truck dies just as it would disconnecting the stock wire on any other diesel. The trouble is, with it being connected in the cab where it is, I often kick it loose when I am wearing snow boots and the truck dies. It is hard to drive in traffic like this and I imagine it will be harder to push snow if I keep killing the truck by kicking the wire off.

So, why would someone have added this wire? What did they bypass? Something has to be messed up somewhere or the prior owner wouldn't have added a whole new wire. I am more interrested in fixing whatever went wrong and having the thing done right rather than risking a hard-to trace rig-job in the middle of a snow-covered parking lot.

I have the Haynes Techbook- Diesel Repair Manual. Unfortunately, there is no wiring diagram included. There are partial wiring pics, but none you can trace a circuit with. Buying the Haynes Chevy/GMC book wouldn't helb because it doesn't cover diesels at all.