Fuel injector wire melted all the way to F/I ECU

1905 Views 4 Replies 2 Participants Last post by Nigel Dax, Nov 14, 2015

Nigel Dax

Discussion Starter · Nov 12, 2015 (Edited)

I was driving my 89 Spider Veloce the other day and under hard acceleration it cut out completely. Smoke started coming out from underneath the package tray then I saw smoke coming from under the hood. I parked and turned the key off and it kept getting worse until I ran back and pulled the ground cable off of the battery. Upon inspection, a red wire running from the ECU up to the square main relay then down the harness running under the carpet and through the firewall and all the way to #2 fuel injector. Because of it being next to other wires, those were damaged as well. All of the injectors were replaced 200 miles ago with new. When I reconnected the battery with the key off it started in again. I imagine the melted wire is contacting a constant hot at this point. I am wondering what caused this to happen and will my ECU be damaged? One wire running to the relay was the only one that melted among the other wires running there, I am going to see which one it is. I unplugged the long plug to the F/I ECU and there is no evidence of melting on the plug itself or into the box. UGH.

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alfasrule

· #2 · Nov 12, 2015 (Edited)

The ECU has many protection circuits to prevent it from breaking. It even has a system in it if you hook up the battery backwards.
I think one of your wires may have contacted ground since the injector has 12V on them and the ECU pulls one end to ground to open it.
The main relay may require an inspection, it powers the injectors. The wires to the injector also get brittle over time and may have frayed
and perhaps shorted to ground.

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Nigel Dax

Discussion Starter · #3 · Nov 12, 2015

Alfamelt follow up

I got into the car a little further. I apparently was able to land and power down when I got smoke in the ****pit fast enough that only one wire appears to have been substantially damaged and it did NOT get to the ECU. When I was re-dying the carpet last week I had the package tray out and I did find the Ecu out of it's mount laying on the floor and the fasteners missing. I secured it properly. The main relay was not secured but did not appear to have come in contact with anything to ground it out. From where it exits the relay all the way to injector #2 the wire is cooked. The harness has its' original sheathing intact and show no evidence of being worked on previously other than the ECU and relay unsecured on the floor. My thinking is that if the relay was bad, ALL of the injection wires would have taken a dump and burned. So that leaves the new injector on #2. Could that have caused this? I replaced all of them with Bosch so no Shanghai electronics buuuut? because of the collateral damage to some of the other wires along the route I worry running one new wire from front to back may have another wire that got its insulation melted hiding under the pass through on the dash side of the firewall. Should I just get a new harness or should I say is a new F/I harness even available? I attached pics.

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Nigel Dax

Discussion Starter · #4 · Nov 12, 2015

Update: I decided I would not be able to trust the damaged harness and would have to open up the sheathing all the way front to back to inspect and replace the burnt wire and patch in where other wires got damaged. to many new opportunities for future failure. I was lucky enough to find a replacement harness and plan on just running a total replacement. I need to find out what caused the original failure that limited itself to only the power lead to fuel injector #2. I will replace the main relay and probably put one of the old cleaned up injectors in place of the #2. any other ideas? anybody replace an F/I harness on an '82-'89 Spider Veloce? Any way to test the existing #2 injector to see if it is the culprit?

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Nigel Dax

Discussion Starter · #5 · Nov 14, 2015

So I have ordered a new F/I ECU harness. In the mean time I have checked and double checked anything along the route that may have created an overheat situation on the power wire to injector #2. I am going to change the relay and the injector. I was considering cutting into the sheathing of the new harness and extracting the power wires to all of the injectors and segregating them in their own wrapping. Without having found out what caused the overheat and melt of F/I wire #2 I am apprehensive about just putting in a new harness and have a replay of last week. The original scenario was the whole system shut down and no restart when the wire burned. Is there another forum or group who has someone who may know about these things? I can't be the only person this has ever happened to on an S3 Spider.

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Fuel injector wire melted all the way to F/I ECU

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