I have a 1991 740 wagon (not turbo, fuel injected, Regina ignition) that did the same no-start thing at about 150k miles, and only spraying starter fluid into the air intake would get it to start. I took it to a Volvo repair specialist, who ran some kind of chemical treatment he called a "top-end burnout" through the fuel system. He said it burned out the accumulated carbon on the cylinder heads, which he said was absorbing the injected fuel. Whatever he did worked, as it's started up just fine ever since. Though the starter fluid would get the car to start, I think it poisoned my catalytic converter and oxygen sensor, both of which had to be replaced to pass the state (VA)emissions inspection. BTW, if the starter fluid kills your oxygen sensor, make sure you get the right oxygen sensor for your ignition system (Regina vs.Bosch).

Listen for Fuel Pumps to run when you turn the key to "ON". Electric fuel Pumps can do this. they can die slowly. They usually stay running once the car is started though. Has it ever just died as she was driving?

If it was a Later 200, I would be very suspicious of the Crank positioning sensor. I don't know if the 700's have the same sensor in teh Bellhousing setup.

Is she positive they replaced the Fuel Pump Relay? sounds very much like the culprit.

When you say "wont start" does that mean "wont crank"?

I had a problem of intermittant refusal to crank, that is now solved
after working over the battery cable ends at corroded crimps.
I needed to remove the battery cable assembly and take it to a local
alternator shop and they were able to repair (Solder)the corroded and funky
cable ends. This is something you couldn't do with ordinary soldering tools.
They something like a small bench welder to heat up the cable ends and crimped
battery cable as a unit then used acid core solder.

I could tap the crimp ends at the battery to revive the no-start condition
It would be OK and quit randomly as yours does. Also you could see some corrosion
where the heavy wire enters the crimp.

Intermittant problems are usually a pain to diagnose.

Good luck, Bill

Go to www.stepbystepvolvo.com for free guide to 740 no-starts. As long as you have a constant condition (no-start), then this guide should help you.

When you turn the key to posII, do you hear the fuel pump prime? Have you checked for any OBD codes? Have you pulled one of the spark plug wires to check for spark when cranking?

Klaus
--
Volvoless. Sold the R. There is now a void...

So, at this point you have a new fuel system relay, plugs and wires. My money is on the problem being electrical in nature. Has the RPM sensor ever been replaced? It probably has the Regina fuel system-- the internal contacts in the coil assembly suffer from corrosion which can cause no-starts and stalling. The radio suppression relay is also suspect (you can jumper the fat wires at the connector to test it in a no start situation), and recently we have read about lucid's bad ground for that relay at the front fender.

Ideally, if you can get it to conk out again, check for spark (you had spark when the starting fluid worked one time, you may not have the next time). Check for fuel pressure as well. Can you hear the pump running as soon as you turn the key on for several seconds?

These things are a nuisance, but if possible resist the urge to throw parts at it and narrow down the list of suspects.

Good luck!