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**RaTcheTmasTer** · 09-24-2025, 05:45 PM

Well I solved it!!!!!!!

I hope someone can benefit from my results.
two years ago the truck would not start in my driveway. it would turn over but would not start.

I had changed the coil, fuel pump, ignition module, fuel relay, fuel filter, cap and rotor, about 2 years ago. a new pump worked.

Now to current issue.
My truck stumbled and kept going a few times. Then one day it stumbled and died.
I had no power to the fuel pump. No power to headlights or interior lights.
I checked cap, rotor, ignition module, pump relay, ground on fuel pump. all seemed fine
So I changed the fuel pump. Would not run. I had changed the coil, fuel pump, ignition module, fuel relay, fuel filter, cap and rotor, about 2 years ago as I mentioned.

Well after two weeks messing with it, I had pulled out fuses, disconnected the battery for 30 minutes. I then took a small motorcycle battery and connected the battery to the fuel pump directly at the pump wire. When I grounded it the pump ran! But truck key was not giving power to the pump and it did not run.

Then the next day I got in and cranked it and it started!
I figured I must have done something and that must have fixed it.

Then three days the truck stumbled a few times over 10 minutes and then died.
I noticed the headlights and interior light were out and not working. Truck cranked but would not start.

So I started checking the wires around the lights, battery etc in the dark at 10:30 at night. I did have a flash light!!
Then I grabbed the wire loom at the alternator. I had left the headlights on incase I did something that would kick the lights on. Well when I moved the wires at the alt. post, the headlights and interior lights came on!!!
so I wiggled them again and they went out and a wire broke from the post. I had only been hanging on by a thread!! Luckily I had a wire cutter, a crescent wrench, and fixed the wire!! And it STARTED!!
I couldn't believe what looked like a 14 or 16 gauge wire that was somehow running the computer and/or the headlight and interior lights! Including the fuel pump!!!

Pictures show the wire. Red with fusible link and black insulator that was not on the wire anymore. Connected to the alt post. There is a much bigger wire coming off the bottom. I wonder where that one goes...
I tested wires in the engine compartment and everything seemed normal accept that one wire!

crazy but the gremlin is gone . . . problem solved.

09-24-2025, 05:45 PM	#9
RaTcheTmasTer Automania Join Date: Jun 2009 Location: Pleasant Grove, in the Mountain West. Posts: 361	Re: HELP 1991 GMC Jimmy Lost electrical power to fuel pump Well I solved it!!!!!!! I hope someone can benefit from my results. two years ago the truck would not start in my driveway. it would turn over but would not start. I had changed the coil, fuel pump, ignition module, fuel relay, fuel filter, cap and rotor, about 2 years ago. a new pump worked. Now to current issue. My truck stumbled and kept going a few times. Then one day it stumbled and died. I had no power to the fuel pump. No power to headlights or interior lights. I checked cap, rotor, ignition module, pump relay, ground on fuel pump. all seemed fine So I changed the fuel pump. Would not run. I had changed the coil, fuel pump, ignition module, fuel relay, fuel filter, cap and rotor, about 2 years ago as I mentioned. Well after two weeks messing with it, I had pulled out fuses, disconnected the battery for 30 minutes. I then took a small motorcycle battery and connected the battery to the fuel pump directly at the pump wire. When I grounded it the pump ran! But truck key was not giving power to the pump and it did not run. Then the next day I got in and cranked it and it started! I figured I must have done something and that must have fixed it. Then three days the truck stumbled a few times over 10 minutes and then died. I noticed the headlights and interior light were out and not working. Truck cranked but would not start. So I started checking the wires around the lights, battery etc in the dark at 10:30 at night. I did have a flash light!! Then I grabbed the wire loom at the alternator. I had left the headlights on incase I did something that would kick the lights on. Well when I moved the wires at the alt. post, the headlights and interior lights came on!!! so I wiggled them again and they went out and a wire broke from the post. I had only been hanging on by a thread!! Luckily I had a wire cutter, a crescent wrench, and fixed the wire!! And it STARTED!! I couldn't believe what looked like a 14 or 16 gauge wire that was somehow running the computer and/or the headlight and interior lights! Including the fuel pump!!! Pictures show the wire. Red with fusible link and black insulator that was not on the wire anymore. Connected to the alt post. There is a much bigger wire coming off the bottom. I wonder where that one goes... I tested wires in the engine compartment and everything seemed normal accept that one wire! crazy but the gremlin is gone . . . problem solved. Attached Images Last edited by RaTcheTmasTer; 09-24-2025 at 05:51 PM.