365GT Ignition problem

My father's 365GT was running fine... until last week. He drives the car once every week or two, and prior to this, it has not had any issues. The car started without difficulty, but sounded muted (not rough running), and was way down on power. After driving it a few blocks, he parked it in the garage to investigate the issue and it has not run since.

We first investigated the fuel system. His car has the FISPA electrical pump and the autoflux, although with the FISPA running I don't believe the autoflux is operating, and it doesn't seem necessary. We verified that the carburetor bowls were full, and that the idle jets were squirting fuel.

Next step was the ignition system. We attempted to verify that we are getting spark by attaching a timing light to the spark plug leads and cranking the engine. We got a puzzling result. No spark in 11 of the cylinders, but cylinder #3 for some reason shows that it is sparking just fine. So far after that, we've removed the distributor caps to inspect/clean the points. That appears not to have had any effect; after putting it all back together, we still get spark on #3 and none of the other cylinders.

Can anyone offer some assistance? Or at least suggest the next step? For reference, this is a dual distributor set up, and he has had MSD installed on it.

 

We have figured out the problem and I thought I would update this thread just to bring some closure to it. I'll cut to the chase: It's not very exciting, but it was a bad battery. We did, of course, test the battery as soon as we figured it was a spark issue, and it tested at 12.8 volts. It would also crank the starter easily and for a long time. The battery was not dead, nor was it dying, but it also somehow was enough to turn the starter but not enough to produce the power to the MSD to give spark.

We tested the coils, they tested fine, we tested the alternator, it tested fine, we tested the spark plug wires, they were fine. We had the wiring diagram to the MSD, which is actually two separate MSDs, one per bank. The trouble shoot there was fairly straightforward, but it just seemed really fishy that they would both fail at the exact same moment. So we went back to the beginning, to start again, and instead of just testing the battery, we swapped it for another that we already had. Car fired up easily, and after a minute or two, was running great.

I want to thank everybody who replied to the thread with advice on what to do next. You guys make F-Chat so great. Happy motoring to all.