87 m20b25 in 88 body problems wiring or OBC

[blackmamba1]

I swapped in m20b25 out of a 325is into a 88 325is.

The car will crank but not start.

I know the fuel pump is not turning on but it will if I jumper it.

Also the windows will not go up or down so I assume that the main relay is not turning on.

I looked at this thread:

http://www.r3vlimited.com/board/showthread.php?t=64630&highlight=87+m20+88

It shows this wire as the problem.




But. What about the unloader relay. I think its pin 15. I have that on the chassis side but not the harness side.

What does that do?

Also what are the other 1 pin wires hanging off the ecu.


I also saw something about the OBC needing a code after a swap.

The other option is to take the engine harness off of the other motor and put it on the new motor. That looks like a PITA.

Need help to get this thing done.

[Funkmasta]

I would swap the harness, cleanest way to do it

[FredK]

The green wire on C104 must go to switched 12V to activate the main relay. You can pick up switched 12V at the coil terminal 15. This will allow the main relay to turn on and the fuel pump relay to get energized.

The windows going up and down have nothing to do with the main relay turning on or not. It is the difference in the way the unloader relay is triggered between 87 and 88+ vehicles.

Both the 87 and 88+ cars have C101 pin 18 occupied. It connects the ignition switch to starter through the firewall.

87 cars don't have C101 pin 15 occupied. 88+ cars do.

C101 pin 15 is the unloader relay control on 88+ cars. When it is activated it interrupts the power to the blower motor, power windows, and some other stuff inside the car so that electrical system is completely unloaded during start. On 87 cars, the unloader relay is actuated directly by the ignition switch at C101 pin 18. Right now your car is in an always unloaded state.

In order to get the windows and blower motor working, add a pin to the C101 at Pin 15, and connect it to terminal 50 on the starter.

[blackmamba1]

Ok so...

The green wire goes to the positive on the coil pack..


Not sure which one is terminal 50.. Is that the positive cable on the starter?

Can I splice 15 and 18 together on the chassis side?

[FredK]

yeah, but if your car blows up, don't look at me. :D

[blackmamba1]

I am assuming that when the starter is cranking the relay severs the power.

Once the starter finishes cranking it reconnects the power correct?

So the added pin 15 on the engine side goes to the positive on the starter, it should work correct?

[FredK]

Yes, that is what the unloader does.

Terminal 50 is the smaller of the two lugs.

Terminal 30 is always hot, and is hooked directly to the battery post on the passenger side of the car with a thick cable.

[blackmamba1]

now the only part that sucks is I can't work on the car until Saturday.

[penpen]

what did you do with the coolant hose difference?
i.e. the main hose with the pipe, did u just swap the radiator or the timing belt cover

and the coolant expansion tank location, did u get a 87 and weld the bracket or cover the hole on the left side and use the 88'+ expansion tank split hose

EDIT- nvm i saw another one of your post on your coolant set up

[Unearth078]

ive done this before... i swapped anything sensor related from the later engine onto the earlier one.

do your side mirrors work and how about your blower? you might have a wire not on the starter if none of those work in addition to the windows.

i got all bugs worked out same day doing that

[Unearth078]

also check your ICV if its cranking but not turning over, have someone throw some starter fluid in it. if it gets further with the fluid then usual possibly a bad icv

[Mthrizzle]

I just did something similar ..but have the opposite of what you are experiencing..swapped a m20 from a 89 vert into a 87 is...my problem is the car will start..but wont stay idling...when it does idle..it will do it for 10 mins..then cut off..when trying to restart...the battery is completely dead...any thoughts ?

[TopOfTheLine89]

Did you get the tach and fuel usage gauges to work? How did you wire it if so?

[cheetah993]

I swapped in m20b25 out of a 325is into a 88 325is.

The car will crank but not start.

I know the fuel pump is not turning on but it will if I jumper it.

Also the windows will not go up or down so I assume that the main relay is not turning on.

I looked at this thread:

http://www.r3vlimited.com/board/showthread.php?t=64630&highlight=87+m20+88

It shows this wire as the problem.






But. What about the unloader relay. I think its pin 15. I have that on the chassis side but not the harness side.

What does that do?

Also what are the other 1 pin wires hanging off the ecu.


I also saw something about the OBC needing a code after a swap.

The other option is to take the engine harness off of the other motor and put it on the new motor. That looks like a PITA.

Need help to get this thing done.

Is that why my tach, mpg guage, and clock don't always work? If so, then can someone tell me where that plug is and things to look for? Have had the car a year, asked on bimmerforums and no one could help. I have Switched the si board and the cluster itself and still nothing. Any help on this would be amazing. Thanks.