Motor to Body compatibility?

#1

Group, I recently dropped a 90 I motor/harness into an 89 body, and the first turn of the key yielded a bunch of smoke and a set of burnt wires. This problem is way above my pay grade, but while I wait for the shop to unravel this mystery, a friend shared a similar story, where he dropped a 90 harness into an 87 car, and appeared to smoke the same wires.

His (the friend) assessment of the problem seems to meet at pin 20 of the circular connector (big one next to the fuse box), and according to his research, the motor side of that is a red/yellow tracer going to a relay on the shock tower (and apparently hot), while the body side of pin 20 is grounded inside the car above the steering column. + mixed with - equals smoke.

His solution was to get an older harness and rewire his motor to fit his body. Effective but drastic.

Also, Taxidriver Patton is watching these stories of smoke with trepidation, since he’s putting together a real purty motor with an 89 harness to go into an 86 (or was it 87) body, and wants to avoid his own smokey mess.

So, can anyone on the board weigh in with stories of success (or problems) in the form of:

I (state your name) put a (year of motor/harness) into (year of body) and it Worked/Did not work.

…so we can get a better grip on the issue?

Thanks all,
chuck toasting marshmallows in Atlanta

#2

Thanks, Chuck for posting on our behalf. I, Robert Patton, successfully installed a "87iI engine and wiring harness into a "86e series car. No problems with this repower as it lives in the Mayberry Police car .However, based on your recent misfortune, I now have concerns about putting an "89i engine/harness into a '87e series four door car. Others, please share your repower success stories. Regards, Robert (taxi driver) Patton

#3

Post Script: Chuck you should tell the group about your '89 engine/ harnesses into '85e series cars.Round hole into a square plug (literally), but it can be done… Regards, Robert.

#4

Chuck, I forgot about Laura’s engine/ harness into "Rusty," the car that Cullen recently sold. That was an '89i engine/harness into a '90 i car. Thus, the same swap that you just did—without the smoke. Just adding to the confusion, Robert (isn’t electrical work fun) Patton

#5

I have put an '87 325is motor in an '86 325es body. No major problems and certainly no smoked wires. The ecu connector won’t fit throught the smaller hole in the firewall (get out the rat tail file) and you have to improvise on the right shock tower ground connection.

#6

I believe that if I were doing an engine swap, I would also swap the wire harness from the donor engine also. Def a PIA, but at least you avoid wiring incompatibilites.

#7

bmwbadboy wrote:

I believe they are swapping the wiring harnesses, but trying to avoid rewiring the fuse boxes. At least, that would be my guess. I’m just glad I’ve got two 87s…