I have a 1990 Volvo 740 sedan. Although a dodge man and a multiple Ford Taurus owner (very long story..) I have ventured into the foreign car universe and the set up is quite different inside of these Volvos to me. I can't get this car to start and the fuel pump won't souñd. I have a new one and just recently got the old one taken out then hooked it to my battery charger and it actually worked. This car is a mess and has sat for a year. Some of the fuses are missing and I was wondering who had the fuse layout for this 1990 seda? If that doesn't fix it and there is a wiring issue and instd of a toggle I might want to just hook it to a component that turns on only when the key is in the n position. Anyone have any suggestions?

 

fuse layout for your car should be on the back of the ashtray.

the fuel pump is run by a relay (2nd from the left in the middle row forward of the fuses), which is triggered by the ECU (EFI control unit), it runs about 1 second when the car is switched on then stops, when the engine is turned over it starts again. btw, note that unless your car has 'regina' injection there are TWO fuel pumps, one is in the gas tank and is just a 'primer' pump, the main high pressure fuel pump is under the car. Regina cars have a high pressure pump in the gas tank and no additional pump.

I don't have the wiring diagrams for a 1990, but a 1991 should be pretty similar, the fuses on a 91 are...

1 - 25A - fuel injection and ignition system
2 - 25A - hazard lights, headlight flasher, central locking
3 - 15A - power seats
4 - 15A - brake lights, shifter park lock solenoid
5 - 15A - clock, vanity mirror, glove compartment light, trunk light, courtesy light, radio, power antenna, door open lights.
6 - 30A - electronic climate control (only on some 740's)
7 - 30A - fog lamps front and rear
8 - 30A - power windows
9 - 15A - turn signals, seat belt warning light and reminder, relay for power windows and seat heaters, relay for electric cooling fan, manual climate control, relay for parking shift-lock
10 - 30A - heated rear window, power sunroof, heated mirrors
11 - 15A - in-tank fuel pump, O2 sensor pre-heater
12 - reverse lights, OD relay, bulb failure warning circuit, cruise control
13 - (diesel stuff)
14 - power door mirrors, cigar lighter, radio, tailgate washer/wiper (wagon)
15 - power seat relays, horn, windshield wash/wipe, headlight wash/wipe
16 - heater/ventilation fan for manual control.
17 - left high beam
18 - right high beam
19 - left low beam, relay for front foglamps
20 - right low beam
21 - left parking lights, license plate lights
22 - relay for front fog lights, right parking lights, rear seattbelt and ashtray light, gearbox selector light, storage box lighting
23 - heated front seats
24 - spare
25 - rear fogs
26 - optional radio amplifier.

(my diagram for 1991 is unreadable for fuse 12-26 values)

 

Thx for responding and I don't believe it's the Regina but regardless I have the main pump and heard no pump period. Are the fuses numbered on the fuse box? How often do relays go bad on these things?

 

i'm pretty sure fuse 1 is the leftmost.

the relay is 23 years old now, its due. Do be sure to replace it with either a genuine Volvo one, or a Stribel (they make the volvo ones... logo looks like a circle with an S in it crossed by two curved lines like )( ). IIRC, the fuel injection/pump relay is usually white. its actually a double relay, one half powers the ECU and other stuff and comes on with the ignition switch, the other half powers the fuel pumps and O2 sensor heaters and stuff, and comes on when the engine turns over (and 1 second when the ignition is first turned on).

there's another important relay on a 740/940 under the hood called the 'radio suppression relay', which actually provides the power to the fuel injectors. its on the left fender wall.

to trouble shoot this stuff, you really want a volt meter and the wiring diagrams, and actually test the various circuits rather than just swapping parts at random.

 

The relay is divided between the ecu and he pump but can one be out and not the other?

 

yes. one half of the relay can fail while the other half is still working. both halves have to be working for the fuel pumps to come on.