E30 Zone

my tech 1 325i (running motronic 1.0 ) and I have no spark the TDC sensor pickup had fallen off the flywheel but this has been repaired, and both crank sensors have been replaced. I have also tried a second ecu. the coil has a good earth when the ignition is off, but no earth when the ignition is turned on, is this normal? somebody help! haha

Have you got power to the coil? Think the ecu grounds the other side of the coil to create the spark.

Hi, thanks for your help. I have checked and the sensors are connected the right way round, and they are also giving the correct resistances although I don't know how to test if they are actually sending a signal. The coil is getting 12v and the earth side is getting a good connection to pin 1 on the ecu, but for some reason the ecu isn't switching the earth

Have you tried a different ignition coil?

Also check the engine-to-body earth strap, and the rotor arm. Also worth measuring the resistance of the HT leads - they should all be under 10 kilohms.

Hi , yes we've checked all of tjose, the problem liesxwith the ecu not switching the coil earth. If i take wire to earth and flash across the coil earth terminal i can create a spark, but i have changed the ecu and the crank sensors and the ecu is not switching the earth :/

Maybe worth trying a third ECU - the early 073 type was reknowned for failures due to dodgy solder joints, etc. (It's a twin PCB design).

Hi, yes the fuel pump runs during cranking. Also the second ecu i bought was seen running before i bought it last weekend so im assuming it still works!

I would use a multimeter to check the ECU socket pins are getting the correct power and ground, and sensor/coil inputs, as per the pinout diagram:

http://www.e30zone.net/e30zonewiki/inde ... CU_Pinouts