M30 motor using M20 loom/harness?

[weaksauce]

way to go!

i got a box full of new hoses and gaskets in yesterday afternoon for mine. I am replacing everything rubber or gasket wise on my B35 before it goes back in the car.

[Paz]

Sweet, it runs!

Turns out the M20 loom was damaged and repaired badly.. Well, it just wasnt repaired. Once i found that out i had fuel but it still didnt run, so swapped the crank and spark sensor wires around and away it went.

Now to finish the prop (im gonna use an M20 2.5 output flange on the back of the M30 box and it should let the 2.5 prop fit, bolt up the exhaust and its done.

[Erick]

spark sensor.

I knew it! :p

When I said oil pressure plug I was like "that really makes no sense... but I can't think of what else it could be.

Yeah, what Nando said. (please don't ban me Josh)

[nando]

On M20s the passenger side is for the crank sensor, drivers side for the spark sensor.

[Paz]

Yeah, i can get it cranking by adding a bit of the M30 loom, its like another feed from the battery +ve to the main pin on the starter solenoid. Then it cranks off the key..

I'll need to charge the battery and swap the crank and spark signal wires over (as im not sure which is which), but im sure i did that yesterday to no avail.

[nando]

if you don't get a crank signal to the ECU, you won't have spark and the fuel pump won't turn on. did you get it cranking over at least?

[Paz]

Yeah i checked all the c101 stuff out today, the only thing different is the 318is harness has an ABS something in pin20, the M20 harness has a ground for the coolent sensor apparently. I got rid of the ground upon recomendation from a friend..

Did some digging at key points and found i have voltage at the main relay, voltage at the coil and voltage at the starter switch pin in the C101 connector. I dont have any voltage at the fuel pump pin, and i dont think i have any spark.

Will carry on digging.

[yert315]

They should match up fine, assuming you have the correct plug. If it plugs into your body side harness fine, your wires will match up like they should. No swapping of pins necessary

[Paz]

Im just wondering, are the c101 loom and body side the same? I just read someone said the pins didnt line up and would need swapping around.. Need to check for some pinouts on the c101's..

[yert315]

There should be three terminals on the starter with 4 wires connected to them (two of which go to the middle terminal).

As far as the spark and cp wire, just switch them and see if you get spark.

[Paz]

I wonder if i have enough main power leads in the M20 harness, hence having to connect another live to get the starter to crank. I have two power leads coming from the body harness, and i think only one that comes from M20 harness. I have some other leads that are earthed/grounded to the strut top, i wonder if this is wrong... But im sure i copied it from another 325 correctly.

Also, on the crank and spark signal plugs, identical as you said, is there any way of identifying which plug on the harness is for which sensor?

Thanks

[LowR3V'in]

I'm also using the m20 harness with no problems.

[Erick]

I'm using an '89 325i harness. I actually went the extra step into wiring the injector twist clip for easy removal (given I'm just driving this M30 'til I blow it).

I dont remember doing anything crazy, but have you made sure that you connected everything in the right place? The crank position sensor plug and the oil pressure plug are identical and go side by side. Easy to confuse those.

Check all connections that could've been mistaken and go from there.

[e30_kid89]

I've used my m20 harness to work on my m30b34 with b35 electronics and on the stock m20 computer. It started up first try and idled fine, never drove it though like that, I did away with motronic to run MS before fully completing the car - again re-using the m20 harness :D

[chadthestampede]

I used one, it worked great. Just had to extend the afm and fuel level sensor wires. I used the m20 cps as well. And the m20 alternator. And power steering pump. Just an fyi, you'll need to run a wire from the c101 to the starter to get your windows and blower to work.

I'll try to find some pictures. If you have all the wires though it should work perfectly fine. I don't remember doing anything special, but I'll look at my notes and see if I wrote anything down.