M30 no spark after e34 harness swap

[kronus]

We decided to swap the motor harness out of our lemon to one that wasn't quite as hacked together with butt crimps.

Prior to harness removal, the engine ran fine. Nothing except the harness was removed.

The old harness was out of a '89 635csi, and the new one came out of a running '89 535i.

Everything is hooked up and it cranks happily all day but does not spark.

After a day of poking at it I'm getting most of the way toward stumped. Here's the things I've checked:

- main relay turns on in ON/START
- fuel relay turns on when cranking
- all ecu power pins (18, 37 through main relay pin 87, 27 through coil pin 15/+) get power
- all ecu grounds (19, 2, 14, 24) have continuity to ground
- CPS continuous to ECU connector, 511 ohms
- coil gets 12v at both terminals in ON/START
- tried three different ECUs
- tried shorting the main relay connector instead of having the ECU run it

Any ideas on things I might have missed? I really don't want to put the old harness back in, it sucks.

[kronus]

Update, went through this awesome post but found nothing abnormal. Still stumped.

[ThatOneEuroE30]

Have tried doing the same as firebird swapping harnesses for another e34 harness.

[kronus]

by the way this turned out to be me feeding +12V to the OBC kill wire (pin 8 on the C101 connector) instead of floating/ground like it wanted.

[ThatOneEuroE30]

Glad to here you got yours
Figured out. I think I got mine. We will find out tomorrow after class

[kronus]

nice. good luck!

[Red88]

Thank you for posting your solution instead of leaving another thread at a dead end!

[Ether-D]

Thank you for posting your solution instead of leaving another thread at a dead end!

True dat!