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Discussion Starter · #1 ·
I have an 89 chevy 1 ton crew cab (I think it was an old forest service truck) it is the older style square body, 350 tbi model with the fuel module unit. To tell a little back story, I had not driven the truck in a few years and was thinking about selling it. I charged the battery and fired it up and took a video to send to the person interested but never ended up wanting to sell this old girl. Months later we where going to move and I had planned on getting the truck rolling and limping some loads to the new place but when I went to start it, it would just crank and not fire off unless I threw gas down her throat. Thinking it was something simple like a bad fuel filter getting clogged from the last time I started it with old gas in it but the new filter did nothing. I later realized I was not hearing the fuel pump at all so I changed the pump relay hoping for a quick fix so we could get moving but that did nothing as well. We ended up towing it to our new place so I could either figure it out or get rid of it later. I was testing the relay and replay plug to see if I was getting power which I was and could hear the relay click. Fuses are all in order as well. Going through some grounds in the front and cleaning them up did not set anything straight. One day I had been checking wires and went inside to mess with the tank selector switch and thought I would turn the key on and listen for a pump and I heard it for the first time! I fired the truck up and let it idle for a bit while I went inside just to hear it slowly surging itself to sleep when I came out as it seemed the fuel pump stopped working again and could not get it to fire up. turning the key on and off I got it to come on again and after it did not fully fire I then heard the 20 sec fuel module signal pop on and was able to get it running for a tiny bit once again. During this I was trying to get the fuel tank to switch but it would just kill the truck either from it not doing it correctly or the tank being empty or that pump just not working. I have never been able to recreate the truck firing up after that sadly and I have gone back and messed with some connections and the tank selector switch with no luck. I am getting power to the relay and I am getting power up to the tank selector switch. I probed the tank switch plug and I tested the tan/white (C) power to the other 3 (ABD) plugs and got around 11-12 volts testing it with each of those plugs (Not sure if ALL of them are supposed to read like that or not?) I am not very knowledgeable when it comes to electrical so I am baby stepping myself through what I can. A few other things to add: The fuel gage always reads way past full no mater what tank the switch is on (RH tank was the only one working when it fired up anyways) and I also had replaced the ignition control module a while ago but that was obviously fine. I am trying to get this thing running so I can do some work around my property without spending a arm and a leg replacing the usual string of parts people do when troubleshooting these types of issues. Any assistance would be greatly appreciated. as I have so much going on that my stress level is out of control.
 

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It sounds to me like you're grounds at the tanks aren't making good connection. Also there's a ground under the dash to the left of the steering column. With an open connection your fuel gauge will go to overfull. Remove the ground wires, polish/grind the area, inspect the connectors, and reconnect them.
 

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Discussion Starter · #3 ·
It sounds to me like you're grounds at the tanks aren't making good connection. Also there's a ground under the dash to the left of the steering column. With an open connection your fuel gauge will go to overfull. Remove the ground wires, polish/grind the area, inspect the connectors, and reconnect them.
Hmm alright, ill give it a go when these storms leave the area. I am curious about the ground under the dash you speak of. If it has some impact on the fuel system then I am very suspect of it since I had those 2 random times I could actually hear the pump kick on and actually get the truck to start and I had no clue what had been different (then truck went back to no fuel pump). Maybe I bumped it and kicked things on for a bit. Odd thing is the tank was reading super full still, those times it randomly worked. I will try to clean up those grounds though.
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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The tank ground should be on the top of the frame rail near the filler neck under the bed, 13mm screw. If I recall correctly, there is a pink lead for the pump +12V, gray? I think for the fuel gauge sending unit output, and two blacks, one with a white stripe. One goes to the frame grounding screw, the other back to the fuse panel where it’s grounded.

It’s been over a year since I’ve had to be under there so I could be slightly off.
 

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