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Old 07-13-2019, 09:46 AM
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Default 1996 GMC 1500 pickup

I am having an issue and would like to tap into the knowledge base here about my 1996 gmc pickup, 4.3, 5 speed rusty crusty 180,000 mile truck.

I was out and about and it quit, just pulled up to stop at a stop sign and it just died, I was in close to a parking lot and pushed it over there and did some checking. Squirted a little starter fluid in it and she popped off. It was about 4 miles to the house. Got it home by rigging a squirt bottle with a hose and gas into the top of the throttle body and manually pumped gas into the air intake to get home. Yes I have a video my son in law took.

On the way home I had nothing past the cab electrical wise, no fuel pump, tail, brake, signal, license lights nothing. The fuel gage does not move when I cycle the key.

No blown fuses in any of the boxes, under hood or dash.

I think I have lost a ground to the back of the truck, or is there a connector along the frame that carries the wire harness to the back of the truck? I have not had time to get under and go shopping for it just yet. I thought there might be a connector as the trucks have different wheelbases and the wire harness would be different dimensions for those.

The truck sits much of the time when the weather is dry and hot I just ride the bike everywhere. I just happened to use the truck because I had not used it in a few weeks.

Thanks

Scott
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Old 07-13-2019, 10:10 AM
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No help here but did you try a jumper for the ground?
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Old 07-13-2019, 12:39 PM
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No but I will run one with the jumper cables

Thanks for helping

Scott


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Old 07-13-2019, 12:43 PM
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Check and see if you burned up a fusible link.
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Old 07-13-2019, 02:55 PM
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I'll give that a go,

Thanks for the suggestion.

Scott
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Old 07-13-2019, 09:42 PM
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Several years ago in my 1990 gmc, I developed an exhaust leak in one of the manifold donut. A buddy was driving it hauling a load of scrap to the scrap yard for me when the truck died on the way there. I had an idea what happened, and was right. The hot exhaust burned thru the wiring harness running to the back and took out the fuel pump wire. Went and rescue him with some wires and wire nuts. Learned a lesson that should not let an exhaust leak go unfixed.


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Old 07-13-2019, 10:55 PM
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Check your relays most all that runs through relays you also have a main fuse check it.

Then check the ground to the engine to chassis and ground to chassis and body

If all else fails then check ignition switch they will cause the same issue rare but does happen...

So fuses, relays, grounds, ignition switch... only fusible link I can think of on that particular truck would be the fusible link going to the starter... so if it turns over it's slim that's the issue...

As for grounds, there should be ground from batt. to the rad support, from the engine to frame and cab body, and from frame to bed and one at the bumper to frame.
but I think you have a relay issue m som has same year truck 96 4.3 w/5spd and has had the same issues turned out to be the relays...
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Last edited by MetalWolf; 07-13-2019 at 11:02 PM.
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Old 07-13-2019, 11:16 PM
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UPDATE: Nevermind, I didn't read your entire post. As for harness issues I have nothing other than good ol' tracing harness routine...

My first thought was fuel pump. Yes, they just "go", especially after sitting. How is the fuel pressure?

Kudos to you for getting it home on a squirt bottle! We DEMAND to see pictures or video of this! Or link to your gootoob page where you should be monetizing your plight!
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Last edited by mccutter; 07-13-2019 at 11:23 PM.
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Old 07-14-2019, 05:18 PM
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Well I am leaning to a bad fuel pump. I chased wires jumpered out the relay and pulled the plug at the fuel pump, I have good power at the gray and black/white wire, these show the power and ground to the pump. I cut a hole in the bed. This truck is way beyond a show piece so to hell with a tank down or bed up.

I checked for continuity through the fuel pump motor and have none. That shows me the motor circuit is open and the pump is gone. There are 4 wires out of the pump connection on top of the tank, black/white stripe, purple, gray, and one to frame ground, it is part of the fuel gauge. When I pulled the plug the fuel gauge went to full.

I do not know why this would mess with all the blinkers and such?

So lets shop for a pump shall we.

The sun is right on the truck right now. later I will pull the battery out and jumper over to the pump directly and test for final time.

Thanks for all the comments and suggestions.

video uploading to the tube now.

https://youtu.be/6YIq3U7w9jg

Scott

Last edited by Scotts; 07-14-2019 at 05:29 PM.
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Old 07-16-2019, 12:39 PM
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Just because you have battery voltage with an open circuit doesn't mean you have it when connected. Each resistance in the circuit takes part of the voltage, or the correct term is a voltage drop. I have seen wires worn down to 1 strand out of an 18 gauge wire that will show battery voltage on an open circuit, but as soon as you connect the load the voltage goes to zero. In this case an ohm meter will lie to you, 1 strand of the wire will carry the tiny amount of current that the ohm meter uses.

Be wary of the open circuit voltage, same scenario as the ohm meter, almost no current will read okay on your voltmeter. I try to use voltage drops for my testing.

In your case on initial testing I would use back probe pins and check for battery voltage across the pump. That tells me I have a complete circuit and if I see less than battery voltage I know I have a resistance somewhere else. next is to test positive side to ground, should be battery voltage if not I know I have to chase it to the source.

Don't forget the ground side of the circuit. Once again looking at voltage drops, with the load connected back probe the ground side of the pump and run the other lead to a good ground. Voltage read here indicates a resistance in the ground circuit.
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Last edited by Dr Dean; 07-16-2019 at 12:41 PM. Reason: attempting to clarify my jabbering
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