Have had a series of no start problems with this 1990 740 non-turbo wagon.
When I aquired it the mechanic believed it was the FI ECU.
This brick is Belgium made and the ECU is odd. It's a Siemens.
The word I received was that this particular ECU is more dependable than most so I persued other possiblities. The no start condition seemed solved after replacing the crank sensor. Not long after I was again dealing with a no start condition. On a suggestion from this message board I swaped the relays on the passenger strut tower (radio suppression / aux cooling fan). This corrected the no start condition.
Not long after my no start happened again. I have not yet replaced the radio suppresion relay with a new one, I'm still using the exchanged one.
Ok enough history, current condition is:
I turn the key and hear the fuel pump kick on.
I turn the engine over and it just cranks and cranks.
I have not detected any spark.
* What is the safest and most dependable way to check for spark?
Some times the engine seems to give a slight cough just as I am letting go of the key when I cease cranking.
* Could this be important?
The weather has turned colder since the last successful start, but this may just be a coincidence.

Suggestions?

Thanks

Richard