You folks gave me a tremendous amount of help with my first 240, prepping it for my son. I'm at a friend's house now, trying to pass the favor on. Unsuccessfully, so far... so here's a question...

He's got a 1991 240DL that's had intermittent starting and rough idle problems. Now, it won't start at all. He's swapped the coil, the ignition amp module mounted close to the front driver's headlamp, the ECU (the current one in it is a Bosch 531), the fuel pump relay, and the crank position sensor in the past month or two.

There doesn't seem to be any spark at all. Nothing at the plugs, nothing at the high voltage wire going to the distributor cap, no high voltage coming from the coil. We swapped in a known good coil from a 1989, and no change in symptoms. There is voltage at both low voltage terminals of the coil when the key is switched on, but no pulsing of the test light when cranking. There is a DEFINITE strong pulsing in his running 1989. It would seem as if the problem is before the coil, but I don't enough about the electrical system to diagnose it further.

I've read the 700/900 FAQ articles pertaining to ignition, but I confess a lot of it is a bit over my head. Are any of you willing and able to give me step-by-step pre-coil troubleshooting instructions that an idiot can follow so I can be the hero here and help him get his car running?

Thanks in advance for any help you can give..

Barry