Hi __?___.

You were pretty creative with the starter switch in that other car,
which reminds me that 740's have a chronic intermittent no start condition
that you can do an easy end run by shorting the starter lugs with a big screw
driver, and needing a screwdriver and flashlight at night. The reason it's so
hard to find the culprit is that the SOB can go months before acting up again.
You put a switch, a more gentlemanly solution than mine.

I just discussed your problem with my Volvo maven, and he says the first
thing you do is get the car scanned for codes with a really good scanner.
You might need to visit Volvo or a quality Indy for this? That makes sense,
and if it points to the culprit, then scout the boneyards or Ebay.

He said you could try Auto Zone etc but doesn't know if those scanners will cut it or not. You could start with a free check at Auto Zone with the idea that it may or may not be 100% reliable. Perhaps others will chime in on scanners?

Happy motoring, Bill