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Discussion Starter #1
I just changed out the engine in my 91. I kept the old wiring harness and everything is back to how it was, but now I’m having a ton of strange electrical problems?

-Check engine light doesn’t illuminate with key on unless ecu is unplugged.
-Starter cranks in KOEO
-Engine does not try to start

anyone know what could cause this?
 

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-Check engine light doesn’t illuminate with key on unless ecu is unplugged...

-Starter cranks in KOEO...
Do you mean completely unplugged? That would mean a gross wiring error, like wrong connectors plugged together. The CEL is usually grounded through the ECU, so normally the CEL cannot come on with the ECU disconnected. If you can trace the CEL circuit and find out why it is on, you may find the root of the problem.

What the heck does this mean? :oops:
 

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Discussion Starter #3
Okay, thanks. I’ll see what I can find tracing that out.

And about the starter, it’s really odd. For some reason, turning the key to on (not to crank) causes the starter to crank bypassing the clutch safety somehow until the key is turned back to accessory.
 

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Discussion Starter #5
Okay, this is silly, I made a mistake in the original post about the CEL.

The I disconnected the wiring to the engine at the junction box, but left the ECU connected which is why the CEL was able to turn on with the engine unplugged.

I think I have all the grounds connected? I have two above the left axle and one over the timing cover.
 

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There should be earth one connecting the head to the right suspension tower, 2 from the gearbox to the left suspension tower area and 2 for the engine harness to either the intake manifold or the block.
 

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There should be earth one connecting the head to the right suspension tower, 2 from the gearbox to the left suspension tower area and 2 for the engine harness to either the intake manifold or the block.
Thanks, I hope I just missed one of those harness grounds

I started disconnecting plugs to get the CEL back on and when I disconnected the IAC, it started lighting up dimly.
Then as I pulled each of the three relays in the junction box the CEL got a little dimmer with each one I pulled so it seems a circuit is finding a ground where it shouldn’t be.

I’ll update when I check those grounds out.
 

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Discussion Starter #8
Okay, that was it! Thanks so much
70141
😁
Yeah I just missed the harness ground, everything is working as it should again.
 
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