M52 E30 Swap Electrical questions

[Scrambler 7]

Sorry if these seem a bit dumb and I have been searching on google for the answers but I've got some free time this weekend and I thought it better to just ask the knowledgeable folks on here because I'm not finding much maybe just thick.

I can't find out where the single pinned e30 temp gauge sensor wires into the m52 engine side loom. I'm thinking it goes onto the engines gauge sender? Although I can't see a single sensor on the M52 engine that looks as though its just for the gauge. So I'm guessing there is a sensor that goes to the gauge in an original M52 car that does other things as well and has a few wires coming out of it? Is the idea to find what ever sends the info to the gauge on the engine and cut that off and connect it to the e30 sensor so it gets the feed from there?

Also really amateur mistake I made. Just disconnected the positive and negative cables on my E36 donor and didn't mark any so now have no idea where the cables go to on the battery posts in my engine bay... The one that comes from my E30 fuse box, does that go to the positive post? There are two more coming from the engine side loom I have no idea where they go. Are they all positive cables? And the battery is simply just grounded with one ground strap? here is a picture:

I marked the cable that connects to the alternator but just to make sure I'll ask here... Does the alternator and the starter have a thick cable connecting the two? If so, does there need to be a thick positive cable coming from the positive battery post running down to the starter solenoid?

Thanks for helping a dummy get his engine swap sorted.

[e30ftw 393]

Temp sensor runs it's own wire to the C101 (Fuse box plug), doesn't join to the M52 engine loom. It just needs to go into the pin it needs to on the body side to make its way to the instrument cluster.

The one you are holding in the last pic goes from Alternator to Starter motor. There will be another large red cable that goes from the battery to the Starter.

The power cable from the fuse box goes to the Battery.

[Scrambler 7]

Temp sensor runs it's own wire to the C101 (Fuse box plug), doesn't join to the M52 engine loom. It just needs to go into the pin it needs to on the body side to make its way to the instrument cluster.

The one you are holding in the last pic goes from Alternator to Starter motor. There will be another large red cable that goes from the battery to the Starter.

The power cable from the fuse box goes to the Battery.

Ok thanks for the help! Was a little paranoid I'd start a fire or something. Do you know where those other cables go in the second pic? One comes from the DME and the other comes up from the engine loom. They would be (+) battery wouldn't they? Thanks

[Scrambler 7]

Having an issue with an M52 swap. Engine cranking but no fuel and probably no spark delivery. Putting it down to engine ECU not having correct signal from auto trans ECU. Found out I had to splice a wire in after I trimmed down my engine loom.

Looking for Brown black wire that comes from auto transmission ECU as I chopped everything out of my engine loom which was related to the automatic transmission ECU which was stupid.

I've got the harness from the Auto trans ECU and it shows a brown/black wire but I'm having trouble looking for it on the engine loom side so I can splice it into any red/white wire as I assume this makes the engine ecu constantly think its in park and safe to start. Is there a diagram someone can put me on to in order to find it? I've undone my engine loom and most of the wires I cut I left length on and wrapped them so I could join back on if something went wrong but I can' find this little brown/black bugger.

"If you ended up with a harness out of an automatic car simply cut all of the wires out of the engine harness that belong to the automatic transmission computer. Automatic transmission computer is wired directly to the engine computer harness; the only wire that needs to be modified is a “brown/black wire pin 26 transmission ECU”. It needs to be connected to any “red/white" wire on the main relay."

http://www.rmeuropean.com/bmw-e30-m50-swap.aspx

I've found my old transmission ECU harness I removed and it has exactly this wire coming from it. I can see most of the wires I've cut pertaining to the auto trans ECU but that brown/black one is no where to be found. Does it come into the auto trans ECU as brown/black then back out of the auto trans ECU as a different wire going into the engine harness?

I've checked all wiring and I'm using a DME that has EWS delete remapped for M3 exhaust and m50 intake I bought from ebay so I'm running out of things that could be wrong. Other wise its the DME/CPS thats bad or both. I would really like to eliminate this Automatic Transmission Range switch though but if all e36's will start without trans ECU then I'm stumped.

thanks

[Scrambler 7]

Can anyone shed some light? Some people have said e36's start with or without trans ecu and other people have said the brwn/blk wire sorted it out for them

[nick496 268]

Having done this recently, I just cut the auto loom out, and didn't touch the brwn/blk wire you're talking about.

I had issues with mine cranking but not starting, and it turned out to be the crank sensor, even though the engine was working fine in the donor car before I pulled it out.
If you've got a scanner, run a scan on it.