535i Crank no start electrical?

[97M62BimmerKid]

Hello all,
I began to have this issue on New Year’s Eve, I went to start my car, and it started, but then died, when I went to crank it again it just kept cranking over, eventually I killed the battery because I’m a moron. Next day got a battery tender and left the battery to charge over night, car cranks strong, but no start. Occasionally I’ll get it to start, but then it dies soon after only to have the same issue.

41F76BFD-2A21-4C8B-87C9-76F8FB054493.jpg

When I bought the car it had the remnants of a long since disconnected aftermarket alarm (probably from the 80s), I have been slowing working at removing the alarm system, and haven’t disconnected anything, but I’ve gotten everything into the drivers foot well, which I decided was a good place for final disconnection. When moving this harness around I found a lot of relays tucked away into locations that obviously were not factory, and I’m worried I may have slightly broken contact with one during the operation of moving things around.

I don’t have a Bentley manual, nor do I really have any diagnostic tools for it, or anything of any real use to help with diagnosing, but I don’t know where to look first. I’m convinced it’s either fuel or electrical related, but I don’t know where to begin with diagnostics.

any advice is appreciated.

[91calysorot]

Check your Main relay at the engine bay. If the main relay fails, it causes no start. HTH..

[97M62BimmerKid]

0A2F5E1F-159A-4E7A-9772-8980F3B4153C.jpg
Here’s where I’m at with this. I disconnected what I assume is the main relay (the dirtiest one, closest to the front of the car) and then a buzzing (I’m assuming fuel pump?) stops, and some lights turn off on the gauge cluster, I sprayed the contacts down with QD Contact Cleaner, hoping that would do something. Nothings changed, I don’t see any cut wires, still finding more relays that should’ve been clipped into place just zip tied to harnesses in the cabin. Still, all crank no start. My fuse box is quite a bit corroded but the fuses that are affected are for the lights circuit.

I also noticed that there are three or four more relays on the other side of the fuse box, what they do, you’re guess is as good as mine. But for whatever reason these appear to have a coating (probably heat shrink tubing) keeping them attached to their relay holders.

These are my findings. I have a multimeter at my disposal if you have any places you want me to test with it, I can certainly do that.

Thanks

[97M62BimmerKid]

Here’s my other idea, which I’ve been toying around in my head. This car was owned by a moron before me. No offense to the previous owner, he probably had no idea, but the wiring in this thing is downright dangerous. I’ve seriously been considering hitting the wiring and replacing every last wire with a new one so that I don’t have to worry about brittle and corroded wiring.

But, once you start diving into those waters, engine swaps and stand-alone ECUs start making more sense. I’ve never been one to give up easily tho, this car was running fine before I removed the alarm harness, and I’m going to figure this out, one way or another, I’ve already ordered a Bentley Manual and as soon as that comes in I’m going to start taking more apart.

more to come soon