I had similar problems this winter, intermittent starting a couple times, but then it failed to start altogether. You checked the power from the starter relay in the fuse panel, but did you check that that voltage made it to the starter solenoid? In my case the problem was corrosion in the connector in the engine compartment on the passenger
side under the cover for the jump start terminal. The yellow wire from the starter relay is routed to the starter solenoid via this connector.

88 S4


Y'all and Greg,
Thanks for the tip. The car has been working for a while, until last night I was stranded at a restaurant. I popped the hood and looked at the connector - it has come apart and the yellow wire was barely in its socket. I pushed it back in and it started right up. A little corrosion but somehow the connector had come apart, not where the two connectors are connected but where the wires come into on one side. I'll be looking at this today.

I did not read the shop manual wiring diagrams correctly to see that this connector was between the start relay and
the starter.

Again thanks for the help,
Brian Scudder
'87 928S4 5sp, LSD - should be starting all the time now