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Author Topic: m42 swapped early e30 won't run, need help!  (Read 3075 times)

cRyan18

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m42 swapped early e30 won't run, need help!
« on: December 31, 2012, 06:24:44 PM »
I'm new to m42 club, but long story short the m20 in my 87 325is kicked the bucket and i had a readily available m42, so i dropped that it.  The motor ran great in the 318 cabrio that it was pulled from, but now I am having issues with it.  The motor cranks and starts every time, but immediately dies.

I know I'm getting fuel, but I am unsure if the fuel pressure is actually in spec.  Going to pick up an in line gauge in the next few days to be sure.

I am also 99% sure i have everything wired right.  The only thing i havent addressed is the green wire from the c104 plug to the obc (comes from pin 27 of the m20 motronic .  I believe it has to do with an anti-theft feature, but if the car already does crank i figured it didnt really matter. I have seen people have issues with this on i swaps in eta cars, but theirs wouldnt start at all. Thoughts?

I've checked for rough looking vacuum lines, everything seems ok.  Stomp test also produces no codes.  Im kinda stumped.  Any other ideas?  Tps, cps, icv maybe?

Any help is much appreciated!  I just want to drive my m42 coupe :)

Chris
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velomech

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m42 swapped early e30 won't run, need help!
« Reply #1 on: January 01, 2013, 05:10:59 PM »
Just a shot in the dark...the pump is getting pressurized and then killed by the anti theft? Maybe run a straight wire to the pump, as a temp bypass to confirm?

Good luck...
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cRyan18

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m42 swapped early e30 won't run, need help!
« Reply #2 on: January 01, 2013, 10:04:39 PM »
Quote from: velomech;118935
Just a shot in the dark...the pump is getting pressurized and then killed by the anti theft? Maybe run a straight wire to the pump, as a temp bypass to confirm?

Good luck...


Sounds plausible.  I might have to try that, or just go ahead wire it into the m42 harness.  I think i've figured it out by cross referencing these dme pinouts.

That green wire from the OBCto the early model c104 plug used to go to pin 27 of motronic 1.1(m20b25).  For motronic 1.1 and 1.3 that pin is for "start input signal from OBC to ignition switch and coil".  I am thinking pin 81 on the motronic 1.7 (m42) might be the same.  It's labeled "OBC code protection input". I'm just hesitant to do that until i know for sure I'm making the right splice.
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