First of all GREAT informative site.. I have a 88 740 turbo. It will not start. Turn the switch on, dash lights up, fuse relay clicks, but main fuel pump doesn't work. Unhooked wires at pump no power. Broke wire?? Also to mention I've put at least 8 gals of fuel in tank, doesn't register fuel either(gauge in red). Just curious would the ECU have anything to do with the fuel system?

Try taking the relay out and shorting the terminals according to the instructions in the FAQ. Also, if your gauge isn't working, it's usually a sign of a failed in-tank pump. This could be because of corroded connections at the sending unit. I just had my sending unit replaced because of this problem. It's pricy ($290 just for the part) so be warned.

Short terminals 30 and 87/2 on the relay and plug it in (no need to turn the ign. key). Both pumps should work. Go outside and bend down and you should hear the main pump bekow car. Take off the petrol cap and put your ear to the opening and you should hear the fainter sound of the tank pump. If the pumps work, your relay may be defective. Try resoldering, if that doesn't work replace it.

To double check if the relay is defective, now without shorting any terminals, plug the relay in and turn the ignition ON, one of the pumps should work. Crank the engine (I assume it cranks), and the other pump should work. You can listen with hoses. If either pump does not work, your relay is defective.
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Kjartan Langskog

hi there,
Does the engine crank at all? Because fuel pumps start running as soon as you start cranking the engine on a volvo. you need to give more info on this.. If it cranks , try to spray some starter fluid and see if it will rev up..
Sammy