Calling all Conversion Owners... or John Walker - help!

76carrera3.2 · 03-30-2006, 08:18 AM

ried Harness

The harness from my ECU shorted out on my 76/84 3.2 conversion. The ground wires were the wires that got all the heat damage. My tech has installed a newer harness but in the process was unable to find the cause of the short. The car runs great now but I am worried that this might happen agian. Any ideas on what to do next? We looked for all the obvious things, wire grounded out on the chassis, negative wire to transmission and so forth and found nothing.

john walker's workshop · 03-30-2006, 08:35 AM

you need to open the old loom with a razor blade and find where the short started.

76carrera3.2 · 03-30-2006, 08:56 AM

Thanks John, I'll give that a try.

76carrera3.2 · 03-30-2006, 11:38 AM

Well i cut the harness apart and the damage seems to start in the back from the ground wires which attach to the intake manifold. There is burning on these wires all the way, not continously, to the ECU. The only other wire showing any heat damage is on one of the yellow wires going to the DME relay. The ground wires got hot enough to burn the insulation off in places and damage the wire insulation touching it. I did not see any evidence of arcing or welding on any of the wires. Everything works like it's supposed to...gauges and so forth. There is no air or cruise control.

john walker's workshop · 03-30-2006, 11:58 AM

are the rest of the normal battery and chassis grounds clean and tight so the tiny ground wires don't have to do the job of the big ones?

76carrera3.2 · 03-30-2006, 12:05 PM

Yes, that was all checked by my mechanic who did the work.

john walker's workshop · 03-30-2006, 12:21 PM

then a direct short had to get to them somehow. are they all smoked or just one or two?

76carrera3.2 · 03-30-2006, 12:28 PM

Just two appeared to be shorted.

76carrera3.2 · 03-30-2006, 12:45 PM

I should add since it is probable related that the engine had died twice before but the ignition had been shut off immeadiately. This time I was attempting to coast into a service station so the ignition stayed on for the time it took to coast about two blocks and that was when i saw the smoke.

john walker's workshop · 03:13 PM

the yellow wires (2) are power out of the DME relay from terminal 87b which goes through #3 fuse to power the fuel pump, and to the oxygen sensor to provide heat to it. one of the two shorted to ground. wires burn from positive to negative. one of the ground wires in that bundle goes to the DME relay, and another one to the oxy sensor.

76carrera3.2 · 03-30-2006, 05:04 PM

John, Thanks. I 'll take a closer look at those areas. The connector to the o2 sensor was smashed on the old wiring so maybe it could have caused the short. Anyway I will check it out.