I have a 97 GMC 2500 truck with the 6.5 l diesel engine. Last summer when it suddenly was not starting as quickly as it had been I replaced all the glow plugs. I discovered that two of the wires on the passenger side harness were just hanging there and not even connected to the glow plugs. One wire's insulation was gone and just bare copper wire. But the harness on the driver's side was fine and with the new glow plugs the engine started fine. So now that winter has arrived here in Fairbanks, Alaska, I decided it was time to get the glow plugs on the passenger side working so I bought new harnesses for both sides on Ebay. I disconnected the old harness from the glow plug controller and hooked up the new harness for the passenger side and connected to the glow plugs. I figured the truck would fire right up the next morning. Fortunately I've got a heated garage as none of the glow plugs were working. Last week we had 0 F. temperatures outside so every couple hours during work I would start the truck for five minutes to keep the engine warm and easy to start. The engine block heater and oil pan heater helped a lot in that regard too.
I've heard there is a Fusible link between the glow plug controller and the underhood relay center that might be burned out. Not sure what this fusible link would look like. Can someone provide me with some clues or photos?
I've just checked the 10a glow plug fuse and it is fine.
So if the fusible link and the glow plug fuse are ok, then likely the glow plug controller needs replacing.
You didn't say if the wait to start light is working. My glow plugs harness to the plugs has fusible link post controler. Did you check power to the stud on top. Do you get power to any of the plugs?
The wait to start light is working. When you ask about power to stud, do you mean the place the glow plug wires connect to the glow plug controller? To check this would mean someone would turn the ignition key while someone checks to see if there is power at those terminals on the glow plug controller. No I haven't checked that yet as I need a helper there. Should have a helper available this afternoon. I haven't check power at any of the glow plugs since it seems obvious they are not receiving power.
Check for power on the heavy lugs of the glow relay.
One lug will be power at all times and the other should only have power during the glow cycle.
If there is not power on one lug at all times you need to check the wiring between the underhood relay center and the glow relay,often the lug closest to the drivers side is constant power but I am not sure how your glow relay is oriented.
It seems the harnesses on my truck are a bit different from the ones I bought from PTWiring. The driver's side harnes from PTWiring has a little additional wire with a plug for something. When I hooked up the passenger side harness I did not dig it out of the mass of wires. I just disconnected it and left it in place. I believe this passenger side harness on my truck has that little side wire with connector. My old passenger side harness has two wires coming from the glow plug controller. One disappears toward the passenger side into that bundle of wires and the other one goes toward the driver's side and disappears into the bundle of wires.
So I decided to just hook up the old harness to the glow plug controller to see what would happen. So now both the new and old harness are connected to the passenger side glow plug controller. The truck starts up like the glow plugs are working. The other day I had to crank it for a long time before the engine fired to life. On Friday morning I plugged in the engine block heater for an hour and the engine started only after a bit of cranking. Today after reattaching the old harness, the engine started normally without using the engine block heater.
The factory harness is not in 2 seperate sections like mine are, as I told you in the email the extra wire is for your PCM signal and tells the computer that power is going to the glow plugs, You have the male end of that connector unless someone has changed it, from the sounds of it if your old harness is in 2 sections then someone has built their own before you got it
Could very well be that it is not the original factory harness. From the amount of electrical tape wrapped around the bundle of wires at some places, I was wondering if it was original factory work.
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