Hugh,

Does your alternator light reliably come on when you turn the key to ON, before the engine starts? It should, of course. If not, I would check the /small/ red wire on the back of the alternator. My 86 245 had a spade connector which came loose on its own.

If this connection looks good, then I would test continuity between the alternator end of this wire and the gray harness connector at the center of the firewall. I had similar symptoms -- dimming headlights, drifting gauges -- yet the battery managed to intermittently charge enough that it took me awhile to figure out what was going on. Reconnecting the small wire straightened things out.

I don't doubt that general harness deterioration could be affecting the FI, but I'd also make sure the fuel pump is running during cranking (if you can't hear it, disconnect the return line on the driver's side firewall to check) and check spark to make sure the ignition ECU is good.

Tim Canan, Minneapolis MN, 1980 245DL