my car keeps smoking engine harnesses

[kman_e30]

a few weeks ago my car stalled out at the track, after that it wouldnt start back up, we thought the starter went out, after tapping on the starter the and trying to the start the car the harness started to smoke. when i took the harnesses apart, a brown and orange wire that went to the oil pump was toasted, i decided to swap out the harness with another one, and the car ran fine for about 2 weeks until today.i drove the car to school and drove back home with out any problems, when i tried to drive the car again it wouldn't start, it sounded like the battery died, after trying to jump start the battery and tapping on the starter the new harness started to smoke, i haven't pulled the harness out just yet, but it looks to be the same brown and orange wire that fried, any ideas what could be wrong here?

[UserError]

Likely culprit is whatever that orange and black wire is connected to, or somewhere that the harness is rubbing through on. Burned up a harness, myself, when my baro sensor shorted out.

[ttrousdell]

brown is always ground, no? Too many amps through the wire. My guess a short.

[kman_e30]

could the ecu have anything to do with it?

[UserError]

Solid brown is ground, brown with orange could be a ground, or a positive feed that needed to be indicated different from the other wires in the harness. The ECU is rather unlikely, if only because the circuitry in it is much more delicate than most wires, so the circuit board would be more likely to burn out first.

[kman_e30]

where would be the best place to start looking for short to ground? this only happens when starting the car, when the car is running its fine, also should i try to fix the harness or buy another?

[jlevie]

The starter would have a Black/Yellow wire to the starter solenoid and if a late model a Black/Green wire to the unloader switch. I suspect that the wire that got fried is the wire to the starter solenoid. That being the case, the cause would be a short in the starter solenoid, which would explain both the starting problem and the burned wire.

You could possibly repair the harness, but to do so you'll need to remove the harness from the car, cut all of the sleeving off, and repair the damaged wires (there will be more than one). But before doing that or replacing the harness the starter must be replaced.

[kman_e30]

The starter would have a Black/Yellow wire to the starter solenoid and if a late model a Black/Green wire to the unloader switch. I suspect that the wire that got fried is the wire to the starter solenoid. That being the case, the cause would be a short in the starter solenoid, which would explain both the starting problem and the burned wire.

You could possibly repair the harness, but to do so you'll need to remove the harness from the car, cut all of the sleeving off, and repair the damaged wires (there will be more than one). But before doing that or replacing the harness the starter must be replaced.

sorry i should said that its an early model with the m20b25 swapped in. the last time when i changed the harness i changed the starter too, but is was a used one, how can i check it before i buy another? also i think i found another harness so i dont think all be going through the trouble of repairing the harness

[jlevie]

Unless the solenoid control wire grounding out between the starter and C101, the burned wire (twice) is the diagnostic for a bad starter.

[Gregs///M]

Make sure all your fuses are the correct amperage rating. Often people replace fuses with a larger size and this can lead to harness failure.

[DaveSmed]

Got a meter?

Touch the red lead to the intake manifold, and the black lead to a nut on the strut tower.

Crank it. More than 1 volt? Your engine ground is bad.

[kman_e30]

how many engine grounds are m20b25s suppose to have?

[jlevie]

how many engine grounds are m20b25s suppose to have?

One, from the frame rail to the left side of the engine.

[Gregs///M]

how many engine grounds are m20b25s suppose to have?

You can also measure resistance between shock tower and intake manifold. This will measure resistance of Engine to Chassis ground. Give me a holler if you need a new one, I sell them. Check out my for sale section in my sig.

[DaveSmed]

Measuring resistance wont cut it when dealing with the load of a starter. (or many things)

An 20ga wire would show "good" on a resistance check. But its not going to be turning a M20 over anytime soon. Measuring voltage drop is a much more dynamic check of the circuitry's condition.