1994 Chevrolet 1500 4.3L - Quit Going Down The Road. Now won’t start.
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Customer Complain: The owner of this vehicle stated that his 1994 Chevrolet 1500 with a 4.3L engine quit going down the road and wouldn’t start back up. The vehicle was towed in to the shop and was verified that it would not start.
First Thoughts: The first thing that came to mind when first looking at this vehicle was maybe the alternator stopped charging. It’s a common problem that happens to vehicles, but I soon realized this was not the case for this truck.
Diagnostics: I put a jump-box on the vehicle to see if it’ll start. It did not start. I noticed on the dash that the truck did not have any lights come illuminate on the dash when I turned the key to the run position.
Sorry for the burry picture, but you could see the dash doesn’t have any lights on.
It seemed like the truck didn’t have any power, so I decided to check the fuses.
When I checked the fuses, I noticed that most of the fuses that should have been powered were not. The “ECM - IGN” fuse was the one I decided to chase. It is suppose to have power on it and it did not.
When I looked at the wiring diagram for this circuit, it showed that it is connected to a battery junction in the engine compartment, so it should have a direct voltage from the battery. But before I went and checked the battery junction, I decided to do a quick test.
I took my Power Probe III and, with the fuse out, I touched the terminal going towards the battery junction. The Power Probe III indicated that the circuit was grounded. The complete opposite of what needed to be there. So I assumed a broken wire and it is touching metal in the engine compartment.
I checked the terminals on the battery junction, and they were all good and had battery voltage.
I next checked the main wiring coming from the “ECM-IGM” fuse, but on the engine compartment side. In the picture above, it is the red wire. It was shorted to ground just like the fuse inside the cab on the truck.
Looking at the wire loom on this truck you can imagine that there would be many shorts to ground. The wires are not protected from the heat or from rubbing on sharp corners. The next step I took was to check the wires behind the engine. There has to be a wire broken back there.
After about ten minutes looking all down the wiring harness, I did not see a wire broken or exposed or touching metal. What is going on?
I checked the red wire again in the engine compartment and it magically had 12 volts! I turned the key on and everything had power and it even tried to start. I messed with the area that was shorted but didn’t even see the problem . Then after about a minute, it went back to being grounded.
I decided to double check myself, starting from the battery junction.
Right behind the other wires at the battery junction, there was one wire exposed and touching the firewall. I almost did not see it. I pulled the wire out and it came apart instantly.
After repairing the wire, which was actually a fusible link that had been rubbing on the firewall, shorted out, and came apart, I checked all the other wires in the harness to make sure none of them were exposed.
After verifying everything was okay, I taped up most of the wiring harness and made sure none of the wires would be exposed again.
I test drove the truck and everything worked perfectly. Fixed!
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