No spark!! :(

[ebbsy93]

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

[gromgsxr]

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

[ebbsy93]

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

[Speedtouch]

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.

[ebbsy93]

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 :/

[Speedtouch]

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).

[ebbsy93]

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!

[Speedtouch]

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