mnotz

Battery was definitely the last thing touched - taking it out 3 years ago, putting it back in a few days ago. Funny enough, same battery, was on the tender, still cranks perfectly. Might not be that great anymore for reserve capacity though. But car was also on the back of a wrecker for the 100 yards or so from the old driveway to the new shop, so not sure what else was shaken around. Battery connections are clean. Single wire ground, the regular heavy wire positive, plus a smaller red wire, which looks aftermarket, probably sound system related from some other indications in the car.

It was stored covered outside all this time. Unfortunately. So I am not sure if it would have dried up to that extent as that's how the car was also stored when it ran fine.

GerritD

In all the replies on your issue, I never saw the cold start injector mentioned.
This together with the thermotime switch is very important to have the car started ! So please check resistance of the thermotime switch (brown switch) and if you get power to the cold start injector during start (max 8secs)

dr bob

These issues would be bypassed by the puff of ether starting fluid test done back when.

For those playing along at home -- The starting fluid test is a quick troubleshooting technique that helps identify pretty much all fuel-related problems at once. If ignition is good, compression is good, the starting fluid will at least give a sputter and maybe a few seconds of run time. As Wisconsin Joe reminds us though, it's at least as dangerous as it is handy. Spraying and making a puddle then cranking, for instance, is a recipe for engine damage. Just a puff while cranking is all you need to help diagnose, and that's all you want. On the 928 with the sensitive cam drive, you MUST avoid anything that looks remotely like a backfire and risk of the engine rotating backwards. Ether risks a light-off in the intake cranking when there's a saturated mixture there, and that flame will continue to a nearby cylinder(s) that still has intake valve(s) open. Engine rolls backwards, belt rides up on the crank sprocket, and you jump time at best, break a cam nose more typically when the engine next turns correctly on the starter.

To the OP's issue, the 1980 car has an aux power feed from the battery to CE panel connection V4, dedicated to power to terminal 30 on the AFC (fuel injection) relay at position XVI. There's a test procedure for checking the integrity of that feeder and the connection at the battery, but the test protocol also has you remove, clean, and tighten the aux feeder connection at the battery positive post before you get out the meter to test. Symptoms of a poor aux feeder connection can easily include insufficient current available to "fire" the injectors, same as a weak AFC relay by the way. To test, remove the fuel pump relay, test for battery voltage at CE connections W2 (red with black tracer) and W3 (red with green tracer) with the connectors in place while cranking on the starter. Low voltage means poor connection. If voltage is OK, reinstall the fuel pump relay or jumper in the socket, crank again. If the engine starts, problem is AFC relay or fuel pump relay. Selectively replace the fuel pump relay and AFC relay to figure out which is preventing start.

Since the no-start magically went away after R&R of the battery, I'll speculate that the aux power feeder connection at the battery positive post clamp was the problem. Disassemble that now, clean it thoroughly with a detailer's brass toothbrush until it's shiny, then reassemble and tighten. I put a bit of Vaseline on the whole battery terminal and clamp after assembly to keep battery fumes from damaging the connections there. The ring terminal from the aux feeder is tinned copper, and the tin is sacrificial when the acidic fumes attack. So when you brush, you just want to remove the dull gray surface film, and avoid going all the way to the copper base metal. No sandpaper please, just the soft brass wire brush.

mnotz

That sounds like such a good explanation and makes total sense. So the additional power feed actually isn't aftermarket or stereo related at all! I will certainly do that. And, obviously continue what I had already started since pulling it into the shop now, which was to once again, clean and de-oxit all grounds, connections, etc., and do the same to the fuse/relay panel.

Thanks for chiming in, Dr. Bob! Much appreciated!

--Marcus