motronic ignition timing - solved

[voyager3142]

i have been having trouble starting my car recently. i found that i was getting no spark at the plugs.

I have read up on how the electronic timing works through the motronic 1.3 to try get an idea of where to start looking for the fault.

so it looks like the coil gets +12v from the ignition and from the ECU when the key is turned to run. when the key is turned to start the ECU is meant to repeatedly ground the -ve side of the coil to create the spark.

i put a 12v bulb across the -ve side of the coil and ground and tried to start the car, the bulb remained on.

Is this confirmation that the amplifier in the ECU has gone and therefore i need a new ECU?

[carannc]

Not necessarily, itc ould mean the ecu is not getting power or is not getting a cranking signal from the CPS

[Brianmoooore]

ECU's are ultra reliable. Crank position sensors are not.

[voyager3142]

have changd the crank sensor once and the ecu is running the fuel pump while cranking the engine, is this not a sign that the ECU is receiving pulses from the crank sensor?

[Brianmoooore]

is this not a sign that the ECU is receiving pulses from the crank sensor?

Correct.

[voyager3142]

so would your next guess be to change the ECU?

[Brianmoooore]

The next thing I would do is to connect a spare sparkplug directly to the ignition coil king terminal, and crank the engine.
It's not impossible for an ECU to fail, but I've never seen one - including a few that have already been diagnosed (by others) as faulty, other than the well known idle control problems with late 6 pot ECUs.

[carannc]

I have one fail but i have to confess to doing some mig welding in the vicinity

[voyager3142]

This problem and this other thread of mine were part of the same issue.

http://www.e30zone.net/modules.php?name ... c&t=130823

Turns out it was the ECU, got an identical numbered one and replaced mine, cracked up on first turn of the key