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M20 Swap - need some help


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I am currently working to restore a 73 with an m20 engine. I have gotten pretty far along, but I am having trouble getting the engine to fire. I am definitely having some wiring issues and was hoping that someone local could provide some assistance. The car came with an aftermarket alarm installed which I have removed, but still unsure if some spliced wires are causing a problem. I do appreciate all the forms and help there is online, but there's nothing like looking at something in person. It turns over with the starter and I have an aftermarket fuel pump sending fuel no problem. My car is stored at my garaged in Redwood City, if you have an m20 2002 and want to stop in, that would be amazing, but if not I would be happy to drive somewhere if anyone is kind enough to let me take a look at their car. Thanks


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First welcome to the site and the bayarea02 club. I'm in Oakland and have a 1974 2002 with the stock m10, but I have experience with m20's, other BMW's and engine swaps.


That looks like a pile of colorful snakes and a hot mess, but nothing that can't be sorted out with some help.


What is the history of the car? Was it running before you started the engine swap?


What is the history of the engine?

Was it running when you got it? Did you see or hear it run?



I would start with the ground wires on the shock tower, they may not be properly grounded. Grounds are very important on a efi engine. Is the ECU bolted down? It grounds through the bolts holding it to the chassis.


You say you have fuel and can crank the engine over with the starter and I assume air isn't the problem. 


What about ignition? Is the coil firing? Is there power to the coil?


If your unsure of spliced wires I would suggest redoing them properly with good connectors and/or soldering and shrink wrapping.


If you haven't already I would get a factory wiring diagram for the 02 chassis and the m20 engine. Then you can identify and label all the wires for easier installation and troubleshooting.


I know there are a few guys locally that have 02's with m20 swaps and lots more on this site. Try searching the forum with the search function.

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Thanks for the pointers. Cars been non op for a while, in great shape, was an automatic (bigger trans tunnel), clean title, extremely happy I found it. The engine was out of the car when I bought it, had been rebuilt (yes I know, why not use it? Wanted a turbo m20 to begin with so sold the engine to pay for my new one and much more). M20B25 off a 92 E30 325ic, 80k miles, pulled it from a totaled car so it ran prior to the accident (got carfax to check it was running). That photo was more of a here's my car and less detailed on the wiring. Still need to check exact compression, but it all sounds good when I turn it over. I ran through the whole engine when it was out of the car to make sure everything was in good condition and cleaned what I could. I'm unsure about the coil. After trying to start it a few times I went and touched the ignition coil and it felt hot so I'm guessing that's a good sign. The coil has its own power and ground so I think my problem is ECU/engine power related. I do have books for both, but with the wiring having already been pulled back, cut, and out of sorts with the old aftermarket alarm, doesn't make it easy. The auto has additional relays which could be causing problems, still unsure. I am going to spend some more time this weekend, I'll make sure everything is grounded properly, but I did run a meter on it and things seemed good.


If I can't figure things out soon on my own I will post detailed photos, but still really hoping that someone with an M20 would pop their hood for me. I would happily take a drive to look at it. Seeing something in person is so much better than photos and drawings. I already looked at an E30 to make sure engine wiring is correct. Thanks in advance to anyone who can help.

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