Need help with grounds

[gerritk]

I have just completed an I/P replacement on my 1997 C2500. Cause was a bad tank of fuel. While I had everything apart I relocated the fuel filter to the alongside the driver's side battery box. There is a nice space there that allows locating a catch can for fuel spillage and stand-up access to everything. I had to splice the wiring for the fuel heater and water sensor. When I got everything back together I went to purge the fuel lines by using the lift pump. I discovered I had no lift pump, no glow plugs and no starter. All the lights on the dash come on except wait to start. The headlights, instrument lamps door locks all work. I get no indication any of the gauges are working (they don't move when the key is turned on). I jumped the lift pump and it works. I checked all the grounds whose location I know about. That doesn't mean I caught them all. The PMD ground is attached, the braided cable grounds on the passenger side frame are good, the passenger side battery ground to fender (the small wire) is tight. I also have a 1999 6.5 suburban (which is running just fine, thank goodness!). It has 3 wires attached to the passenger side intake manifold stud. My truck has only 2. Since I did remove that in the course of changing the injection pump I looked all over for a 3rd wire I might have missed but cannot locate anything loose. Do all these vehicles have 3 wires attached at that point and can anyone tell me what is grounded at that location? Any insight as to what might be common to the 3 things I listed at the start of this thread? I'm thinking it must be a ground, or possibly a dead PCM. The truck was running when I went to change the I/P but the timing was stuck way advanced due to ingression of crud. There was so much crud it collapsed the filter element and got into the pump.

I also was wondering if it is possible that either the fuel heater or water sensor could have swallowed a bunch of water or some substance that shorted out one or the other. The water in fuel light never came on. Is anything grounded at the fuel tank that could cause this? I did pull and clean the tank but I don't remember if there were any ground wires back there.

Any help is greatly appreciated.

[Warren96]

There is a ground wire on the tank for the fuel gauge just above the differential on the front facing side of the tank. Good luck! keep us posted and let us know when you find the problem!

[gerritk]

I located the pcm ground, it was attached to a stud way at the back of the engine. But the problem turned out to be a bad ignition switch. All is well again.

[Robyn]

Ign switches are or can be suspect in the older rigs.

Glad you got it fixed.

[cowboywildbill]

Yep it's always fun tracing things out. Glad that you found it. I've seen people pull their hair out with trucks that have a BCM. They will have a tail light out or something of that nature and run a separate ground to solve the issue , only to find out that the light stays on after they shut everything off.
Some grounds are completed by the BCM and the component always has power going to it. And the BCM completes the ground to make it work.
Once you get them to understand the concept of that, they usually figure things out.
Then there is the signal wires. Whole new ballgame. Ain't it fun ?