87 4.0 not starting have a few questions.

1987 cherokee pioneer 4.0 Renix

Story: replaced front driveshaft and took the car out on a test drive. Voltage gauge on dash fell to zero and i smelt buring wires coming from under the hood. turned the jeep off and got it towed home. In the morning i discovered a burnt wire that i believe is connected to the starter solenoid or starter relay located on the passenger side firewall close the battery. replaced the wire and had the battery tested. Battery came back bad so i bought a new one. Voltage gauge still reads zero. Replaced all four relays located near the diagnostic connector because i could hear loose pieces inside when i shook them close to my ear. Checked all fuses, all are good. Still no reading on the voltage gauge. All other gauges are functioning and all other electronics seem to be working as well.

My question is how the gauge reads the voltage and where is it connected in the car. Also does the gauge need to be functioning in order for the car to start ( does the jeep need to know it has power to start?).

I have not checked for fuel and spark yet but i will be later on tonight.

Im thinking the shorted wire caused the computer to ground out or fail but i am not completely sure.

Any and all help would be appreciated

thanks
Mike

The vehicle doesn't need the guage to start.

Also, on the RENIX models there is a Ballast resistor on the passenger side near the battery, if it fried with the wires, that would prevent start up.....

ok just checked for spark and there is none. Can you please explain to me what the ballast resistor looks like and where it is located? It also appears that the fuel pump is not priming as well. I was going to check for fuel but lightning started so that will have to wait for tommorow.

Thanks
Mike

ok so looked for the ballast resistor and cannot seem to locate it. Was it a TSB on the '87 cherokees? I was just reading up and came across a few posts that said it might be.

This is the ballast resistor. Sorry about the picture but it's bigger on my screen. The ballast resistor is the little ceramic thingie in the front (far right) with 2 wires going to it (both mine are orange). You can jump these two wires and see if that's your problem, however, expect your fuel pump to make more noise. They're cheap (<$10 IIRC)



A bad resitor would not cause no spark, it will cause your fuel pump to cut off fuel pressure as soon as the vehicle starts. Start, run for 2 seconds, die.

ok checked for a ballast resistor and there is definately not one on my vehicle. I checked multiple locations in the engine bay. From what i understand in 1987 the ballast resistor was a TSB and my fuel pump is constantly loud after driving for a while, so i am not surprised that i cannot locate it.

Progress: Checked for fuel and spark, no fuel, no spark. Voltage gauge is still reading zero at the dash with the key in accesory.

Anyone know of a part that would cause all these symptoms due to an electrical short? I know the problem is definately electrical because of the small wire fire experienced during the breakdown.

My only guess right now is that the computer got grounded out and shorted on me. Can anyone confirm or dissuade this assumption?

Im at a loss on this one. If anyone knows a good shop in Tucson AZ for automotive electrical work i would appreciate it.

Thanks
MIke

Just a guess. Could it be you fried a fusible link?

Not sure if they are fusable links. Took a few pics of the original damage.



The green wire in the above picture actually melted and is missing in the picture. Also the cylindrical black piece on the bottom wire is melted.



same wires different angle.



This is where the wires were hooked up to. I believe it is called the starter relay. It is located behind the battery on the passenger side, close to the four relays by the diagnostic connector.

Are these fusable links? i do not have much experience with them. If they are how do i repair them? ( i previously just used a butt-connector to connect the remaining pieces of wire)

Thanks
Mike

87 did not have a ballast resistor.

Yes those are fusable links, possibly bad. That is the starter relay they are attached to, starter relay is possibly bad.

Ignition switch on the upper side of the steering column way up under the dash, could have been fried.

Have you checked all the fuses?

checked ignition switch and all fuses... they are good. The fusable links are definately bad as an entire wire was burnt and is missing in the pictures. Hard to see because the remaining ends are small.

Im going to buy a new started relay just for good measure.

My question is how to fix a fuseable link?

Thanks
Mike

The fusible links are often found at the auto parts store, not necessarily Jeep specific. I used to have the amp ratings for the fusible links, but lost them in a computer crash and have never found them again.
The wire colors (other than red) are indicators of the amp value. But like I said I lost the color and amp rating info.
Maybe somebody has the amp rating for the fusible links??? A junk yard would be a good bet, the dealership is often just too expensive, but worth a call anyway.

Replace it with the same Gauge and length of fuesable link wire.

NAPA and other parts houses sell fuse link wore for this puprose.

poorboy_616 said:

Replace it with the same Gauge and length of fuesable link wire.

NAPA and other parts houses sell fuse link wore for this puprose.

Click to expand...

The fusible link sizes are 14 gauge and 18 gauge. The higher the number the smaller the wire.

If your trouble started right after working on the friont driveshaft, I'd check the harness and leads to the engine temp. sensor, the knock sensor and especially the O2 sensor. The wires often get burnt on the exhaust manifold and may be the origin of your short. The 87 was notorious for this, they rerouted the harness and wires and added some different tie downs in later models.

Checked all my other wires and it seemed the wire grounded out. The fusable link that fried was rubbing against the metal bracket holding the relays for 21 years and finally wore through the coating. Im assuming this because i can see the same thing starting on the other wires. I attached some weatherstripping to the bracket to stop the wires from rubbing.

I still need to know what rating of fusable link i blew. If anyone has either the ratings by wire or by color please let me know

Thanks for all the help!

Mike