I have just bought a non running '90 740 wagon. I dont have it home yet and I will have to tow it 230 miles.

It has a history of sometimes starting but when shut down will not restart for a day or so. The owners have given up on it.

I have read in the FAQ the 3 most likely culprits being the fuel pump relay.
RPM sensor on the flywhee and the Radio suppression relay.

I figure I can eventually find a way to hot wire the relays temporarily to eliminate them as causes but is there a way to test the RPM sensor to know whether or not it is bad. Does it fail open circuit? Does if fail short circuit?

If I put a meter on it on the ac voltage scale and crank the engine over am I likely to be able to tell?

I think it has Regina ignition as it has quite a big black box on the drivers side wheel well.

This is my first gas engined Volvo and it seems in good enough condition to make it run, with about 160k on the clock.

Thanks for any help and advice.

Steve