1991 E34 Engine wont start after engine swap - BMW Forum

pegasusflash · 12-07-2009, 08:07 AM

Hi all , I am new on this forum so I hope you can help me. I bought a 1991 520i recently but the engine failed when bringing the car back from the UK, its a M20 engine. I found a replacement engine its a m20 but it came out of a 320i touring car. The engine has been fitted but will not start it looks like there is an imobiliser switched on as the fuel pump wont pump and there is no spark, the factory fitted alarm appears to be working fine and activates and deactivates. I have changed the ecu as well . Your help would be appreciated, as this is driving me insane.!!

marti5 · 12-07-2009, 08:29 AM

Was the donor car running before you swapped the engine.

pegasusflash · 12-07-2009, 08:31 AM

Yes it was.

marti5 · 12-07-2009, 08:33 AM

Ok why did the original on fail ?

pegasusflash · 12-07-2009, 09:07 AM

I think it was the crank shaft bearings failed. Engine had no compression.

marti5 · 12-07-2009, 09:35 AM

Ok, so it ran but not good....back to the transplant, no fuel pump and no spark, crankshaft sensor.

pegasusflash · 12-07-2009, 10:27 AM

I have two crank shaft sensors and tried both of them on the engine could the two of them be gone?, how do I test them? also the donor engine is from a e30 320i touring car, are the crank pulleys the same on the 3 series engine as the 5 series?, and should I have used the ecu from the donor car it has a different part number han the original one.
Thanks for helping me.

pegasusflash · 12-09-2009, 06:13 AM

You were spot on Marti5 It was the crank sensor, had it plugged in the wrong place, starting now. Thank for you help.