89 E30 / S50 Swap K7 Relay stays engaged HELP!

[///Mpowered]

Hello,
I bought a running s50 that was previously installed on a e30 318is. After switching the x20 wiring from the s50 to match the wiring of the c101 on my 89 325ic I tried starting the car however, couldn't even get it to crank. I checked, and double checked the connections to see if my wiring was off but couldn't find anything wrong with it. Whenever I turn the key to the on position I noticed the K7 unloader relay is staying engaged but not sure why. I swapped the relay with another relay however I got the same result. Pin 30 had power at all times and pin 86 had power only when the ignition switch was on the on position. The other two had no power which seems to correspond to how its suppose to work. Has someone here had the same issue? Any help will be greatly appreciated. Posted a video however, I'm not really good at taking videos lol!

https://www.youtube.com/watch?v=RsLzxEFOSUM

[e30austin]

For your K7 relay power, my guess is you somehow got the two posts at the starter backwards - the terminals should be staggered in size, so you can't get them reversed, but if someone has installed different terminals, it would be easy to get them reversed. One of the posts at the solenoid is switched 12v and the other is a ground - the K7 wire is supposed to be grounded. Either that, or you have an issue with pin 15 at the C101 (black with green tracer, for the K5/K7 relays).

As far as it not cranking, make sure you have the correct pinout for the starter - black with yellow tracer - pin 18 at the C101. Additionally, if your car was an automagic to begin with, make sure to bypass the neutral safety switch wiring, at the ignition switch.

[///Mpowered]

Thanks for reply e30austin. When I bought the engine it came with everything including the computer, engine harness, starter, transmission, and driveline assembled. Essentially all I did was remove my engine, transmission and driveline and set the car on top of the s50 long block and connect everything up. I will go over the starter wiring see if for some reason this was changed. As far as my car goes, at one point it was an auto e30 that was converted way before I bought it. I'm not sure what process was used to fool the computer (not sure if there's more than one way) to be able to run a manual but I'm going to definitely take a look at the wiring. I will get back with my results.

[lukeADE335i]

When you go auto to manual in an e30 there's no need to fool the computer.

You just bypass the starter solenoid (ie. the starter safety circuit mentioned by e30austin) and hook up the reversing lights.

If someone has butchered the circuit - there are some pretty crazy e30 wiring "guides" around the net for going auto to manual that over complicate what is a simple process - then unhook the black yellow wire at the starter, and at the steering column, and run a new wire from the C200 connector in the steering column to the starter.

A post from my thread is here - although my swap was an M30, the starter wiring won't be very different, and a lot of M50 swaps seem to suffer the same "heat soaked starter" problem that I appeared to have, but I now think is actually an internet myth and is just a wiring problem.

Hopefully yours ends up easy to sort - the unloader circuit can be a bit painful to troubleshoot when it goes wrong.

[///Mpowered]

I finally got my car to start, turns out i had a bad engine ground and I also needed to by pass the neutral safety switch at the ignition side like e30austin stated, thanks. Also, thanks for the help and link to your post lukeADE335i I was actually having that same issue where my car wouldnt crank when the engine was hot. I'm not sure if this issue will persist after the s50 swap but if it does now I have an idea of what to do to. Now I have to wire a pusher fan, wire in the oil level sensor of the s50 to the e30 (need to search for diy on this) and fix the leaking brake lines lol! Before i can get it on the road..

[lukeADE335i]

Well done on getting it sorted!