Author Topic: HELP!! swap m20 to m42 Wont start (Read 6898 times)

BoricuaBond000 · « **on:** January 27, 2010, 11:52:46 AM »

Hello Forum,

I will be quick and brief about this guys.......i had swap from a m20 2.5 to a m42 1.8. I have not changed anything, the way i removed the m42(which it was running perfect) I left the harness connected, the only place i disconnected was the ECU and so on....I implanted the m42 with no problem, hooked everything up and it will not start, the Coil packs are new...remember the motor was running in perfect condition. And of now, the car will not start it seems like there is no spark being created. So I then hot wired straight to the starter with push button and then it sparks up, is there anything i need to vhange like relays, fuses and so....plz guys any help would help

DesktopDave · « **Reply #1 on:** January 27, 2010, 12:06:12 PM »

Getting a check engine light? Can you do a stomp test for codes?

BoricuaBond000 · « **Reply #2 on:** January 27, 2010, 05:39:06 PM »

Yea I am getting a check engine light but then again all light appear. I feel it is something with wiring or relays.....also i forgot to mention, I also did a 5 spd swap. Is the swap like the 240sx where you have to loop the Park relay to make it think its in netural?? I know mechanically everything works, I just dont know if there is something specific to look for when swapping from the 6cyld to the 1.8.

e30guydownunder · « **Reply #3 on:** January 27, 2010, 07:45:33 PM »

an M20 chassis loom is not plug and play with an M42 engine loom. I found out the hardway. As to how to fix the issue I don't know. I just swapped out the chassis loom for one out of a 318iS.

Yes you will also have to do something with the automatic wiring regarding the park switch.

DesktopDave · « **Reply #4 on:** January 27, 2010, 08:32:33 PM »

Yeah, there's an inhibitor switch that keeps the car from starting unless the tranny is in neutral or park. Find that switch and short it closed.

BoricuaBond000 · « **Reply #5 on:** January 28, 2010, 06:10:20 PM »

Gentlemen,First thanks and I am apprecaitive for all the help. Is there any way i can get a schematics for all this....I am fairly new to BMW's so Basically I need the bottom harness and i def using the top harness. is there somewhere I can get a diagram for the switch for the 5spd swap? so i can get in there and just fix the problem instead of messin around and trying to find the area of the dilemma.

BoricuaBond000 · « **Reply #6 on:** February 03, 2010, 03:34:32 AM »

Can someone help explian the chassis loom?? Is it the entire wiring of the car?? Where is it located?? Also can someone plz visually or throughly explain where might the switch is for swapping out for 5 spd. Need help ASAP

gearheadE30 · « **Reply #7 on:** February 04, 2010, 09:52:23 AM »

I'd look into buying the Bently manual for both the e30 and the e36. The e36 one has all of the diagrams for the M42, and the e30 one will have all of the M20 wiring information.

BoricuaBond000 · « **Reply #8 on:** February 04, 2010, 02:41:08 PM »

Thank You!

e30guydownunder · « **Reply #9 on:** February 08, 2010, 01:49:35 AM »

Here is a comprehensive list of wiring diagrams

http://shark.armchair.mb.ca/~dave/BMW/index.html

BoricuaBond000 · « **Reply #10 on:** February 15, 2010, 10:04:03 AM »

e30guydownunder- thank You!!

But I have read the diagrams and I am having hard trouble understanding them...and Yes it might be I am amatuer about reading diagrams....But this has gotten to a point of beyond frustration....for something I know is simple, I can understand it. Is there anyone who has done this swap before that can tell me excatly what am I missing and need to be recified?? Please I am in need of HELP!!

e30guydownunder · « **Reply #11 on:** February 15, 2010, 03:38:30 PM »

What year is your car? I have since found out that all c101 plugs after 1988 are wired the same on the chassis side and as such you should be able to plug the M42 loom in a go. If you car was auto you will need to short out the inhibitor switch as mentioned.

Did you remember to hook up the big ground on the engine loom? And did you put the earth strap on for the engine/chassis?

BoricuaBond000 · « **Reply #12 on:** February 17, 2010, 09:09:40 PM »

The Car is an 89 and through my research it should be plug and go.....And Yes! the car was previously an auto, I seriously think that is my problem.....Now the caviot to that is that i can not locate the inhibitor switch. Yo guy, u perhaps know where it is located??

poop12 · « **Reply #13 on:** November 16, 2010, 03:53:30 PM »

5 days ago i've make the same slwap (m42 in e30 84' (m20b20)) but manual ... so i had the same problem no sparking(that was what i thinked it was ...) so i rechecked my wiring swaps with the c101 harness there wer ok ... next was the spark pug cables and coils i've puled out one of the cables put a sprak in it turned the key ... no spark(im not sure if the spark was ok but there was no spark) then i do somethnig stupid bit it hlped me ... switchedthed spark cable 1 with spark 2 and 3 with 4 ... whn i tryed to start there was some strong bangs out of the exhausts ... after that i refitethe 1 and 2 sparks and the 3 and 4 sparks and it startet like new ...