How do you repair a 1990 Volvo 740 GL that won't start but will turn over?

i have 89 gle it was doing the same thing , and it was the fuel injetor relay (black 1 undre the hood) I have a 1991 740 which suffers from no start when hot (engine turns fine). Apparently, and this is from a Volvo trained mechanic I'd trust with my life, the fault in these earlier models lies with the fuel pump relay (which he's replacing in a few days). The relay lies behind and slightly above the fuses which are accessed from behind the ashtray, and in an emergency may respond by being tapped a couple of times. Otherwise wait for around 20 minutes and try again.