1988 744T m46od 191K

This car is occasionally failing to start. Normally you can hear the pumps run immediately after releasing the key and the starter stops spinning. However that does not happen when we experience the no start problem. It is random and is only doing it 1 in 20 times.

I have swapped the fuel pump relay and for good measure did the radio suppression relay as well. The last time it failed to start I just engaged the starter for a short period of time and listened for the pumps to run. After six or eight starter engagements the pumps ran and the car started immediately.

At this point I am guessing it is a no spark situation. I will verify this at the first opportunity. That will be when it won’t start and I have an assistant to crank it over and I can check for spark.

As I have confessed many times electrical problems are not my strong suit. So I would like some suggestions.

What is the best way to trace a fault that results in no spark? My plan was to pull a plug wire and look for spark after putting a conductor in the boot and holding it close to a ground.

How do I work backwards from there to look for a cause if no spark is present? I resealed this distributor and replaced the plastic components in it about 30K ago and the harness is in good shape.

It would be so much easier if it would totally fail or at least do it more often (grin).

Thanks for any insight or suggestions.

Randy