M20B25 swap into my '86 eta.. turns over but wont fire up

[kR00kEd30]

recently swapped out my old eta motor and replaced it with a newer '91 m20b25 with all the electronics from the '91 also...

the car will crank but just wont start... fuel pump turns on but doesnt seem to pump fuel to the engine... hardwired the fuse and the fuel flows fine but the car still wont fire up.. seems as if its getting no spark / fuel to the engine..

anyone had this same problem before? any help would be appreciated thanks.

[jlevie]

My guess is that you haven't modified the car's wiring or the 91 harness (either can be changed) to make the car and the harness compatible. Early production cars (up to 8/87) routed the DME START signal and the tachometer & econometer from the engine harness to the car via C104. Later production routes those signals via C101. Without a START signal from the ignition switch the DME won't turn on and thus there will be no spark or fuel pump operation.

[kR00kEd30]

thanks jlevie

i have the c101 and the harness is a c101 all from the same '91 325i...

what wiring would have to be modified to be compatible?

could it be something with the dme pins?

[kR00kEd30]

also this all came out of auto '91..

could that make a difference?

[BrandonG]

engine to body harness isnt the same look at the pin outs ther different .. hope u didnt smoke anything in engine harness... i did same exact swap

[kR00kEd30]

engine to body harness isnt the same look at the pin outs ther different .. hope u didnt smoke anything in engine harness... i did same exact swap

thank you sir!

[kR00kEd30]

which wires do i need to splice/connect?

[KEVORM]

which wires do i need to splice/connect?

Your c104 plug has 3 wires
Pin #1 Black Wire-Engine speed
Pin #2 green wire-OBC Fuel cut function
Pin #3 Yellow/White wire-Fuel rate
On the 89 harness you'll need to splice or connect the following wires to the ones on the c104.
Pin # 3 from c104 to Pin 8 on the c101 of your 89(Yellow/White or White/Black wire)
Pin #2 from the c104, run a wire from directly to the + terminal on the coil(Green wire)
Pin #1 from the c104 to pin 9 on the c101(black wire)

i got this from: http://www.e30tech.com/forum/showthr...t=28921&page=2

My car is an 84e with a swapped 89i, i have not done the wire splice and my car started just fine......idk what the means for your situation as there are some small differences in every year, but as i understand it only 87's are plug and play which would suggest that my car and your car would both have this issue. Sooooo possibly there is something else going on. I was told by James C (owner of rev) that the only wire i needed to care about was the black one to get my tach to work and that the other ones didnt matter.....just my 2c.

Also my harness and engine were from an auto and it made no difference. (went into a manual car)