Electrical nightmare due to jumper cables

We have a 1988 body with a 1991 5 speed harness and while we were getting the timing done on the engine we ran out of battery. We didnt have an extra battery on hand so we decided to use jumper cables to get the engine going again.

This is the part we messed up. Well, Parts i think.
The vehicle that was going to jump the battery was already running and when we put the ground cable on a grounding point on the receiving truck a wrench fell on the negative wire and caused it to arc on the ac compressor bracket.

After that arc the starter would only click but not turn over the engine.
We decided to let the battery charge and brought another battery just in case. Once both batteries were charged we hooked the truck up again and same thing. 1 click from the starter and nothing AND everytime i turned the ignition key the windshield washer motor would spray. The further you turn the key the "harder" the washer fluid motor pumps.

Another thing we noticed is that the hood light ground cable heats up extremely fast and wants to melt the insulation off the wire.

All main ground straps are brand new and any grounding point surface has been cleaned to a bare metal point.

New ignition switch too. We have looked at countless forums, Videos, and schematics and cant figure out what happened.
We also swapped ecu's

The main gremlins are:
-Super heating small ground wires
-Washer fluid motor engaging instead of starter when ignition key is turned
-no crank or instrument panel light

Whoever has some anecdotal solution please help

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You've got some serious ground loop issues here...If that hood light ground wire is heating up at all, that means you're sending more than 20 amps through it - something that should not be possible when everything is attached properly. If I had to guess, I'd say you popped a fusible link or two, and now the starter is somehow trying to run through the hood light? I'm at a loss as to how this is even possible...

I'm a little confused about this part too..

TonyMontana214 said:

when we put the ground cable on a grounding point on the receiving truck a wrench fell on the negative wire and caused it to arc on the ac compressor bracket.

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The A/C compressor bracket is itself a good ground point, so there should not have been any arc given the negative side of the jumper cables was attached to a ground point already.

Get good cables and battery terminals on the dead truck.

And without looking at diagrams im not even sure the 91 harness would be compatible with the 88 body harness im sure there is differences

Also agree get good grounds and terminals on dead truck

Are there any heavy gauge engine to frame and engine to body grounds?

RichLo said:

Are there any heavy gauge engine to frame and engine to body grounds?

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We removed the old oem grounds and replaced with brand new one of the same style

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Dropped88 said:

And without looking at diagrams im not even sure the 91 harness would be compatible with the 88 body harness im sure there is differences

Also agree get good grounds and terminals on dead truck

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We had a few harnesses from a few years. The 91 plugged into everything normally. The major difference we noticed was the fuel pump harness was a tad different but it works. I must note thst the truck started off fine before the spark


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AK49BWL said:

You've got some serious ground loop issues here...If that hood light ground wire is heating up at all, that means you're sending more than 20 amps through it - something that should not be possible when everything is attached properly. If I had to guess, I'd say you popped a fusible link or two, and now the starter is somehow trying to run through the hood light? I'm at a loss as to how this is even possible...

I'm a little confused about this part too..



The A/C compressor bracket is itself a good ground point, so there should not have been any arc given the negative side of the jumper cables was attached to a ground point already.

Click to expand...

Yea we are completely confused. Whats more frustrating is that we dont even know where to start checking. I must note that the truck turned on fine prior to the spark. Not now.

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I guess I'm still confused when you say the ground on the battery sparked against the AC, both of those should be the same voltage (0v).

Perhaps the jumper cables were swapped on accident and you fried some/all the wiring, and now you have stuff melted together in the harness somewhere?

There should be no ark between negative cable and AC bracket.