740 No Start After Stall While Idling - Need Fuel Pump Relay Info

After starting my son's 1990 Volvo 740 GL wagon for a periodic "run up" and
drive around after a bout two months sitting idle (son's serving over in
Kuwait, car's with me while he's away), the car stalled after about 1/2 hour
of driving and idling. Initially started right up and ran great. Died
sometime while I was away from it for a short time working on the son's
other Volvo, an 83 240 Turbo. The 740 doesn't want to restart - cranks but
no catch. Did try to catch briefly on some starting fluid. Timing belt
seems OK, as I can see the through the oil filler opening on the cam cover
that the cam has moved after cranking. Suspect either one of the two fuel
pumps or their associated relays have crapped out. Basing that on total lack
of fuel smell in engine compartment or at the exhaust pipe after extended
cranking trying to restart. I'm temporarily at a disadvantage w/o a shop
manual for this car. Will get one ASAP, but trying to fix sooner if I can
get some basic info.

Both the main fuel pump fuse and the in tank pump fuse seem OK, and contacts
in fuse block look OK.

What sort of load resistance should I see on the load side of the fuses in
the circuit? Presumably something low if the circuits are calling for the
pump to be running, I would expect to see the pump motor DC resistance
there.

Is there a convenient place to check fuel delivery pressure, like the
Schrader valve on late model Fords?

Can someone tell me the location and pin out of the two relays, so I can
troubleshoot, including temporary jumpering of the relay contacts, which I
believe are a common problem with these cars, just like the 240 series? I am
also suspecting possible corrosion in some contacts in the relay connector
plugs, as its been very wet and humid here since the last time the car was
run.

Yes - there is plenty of fuel in the tank - I added a few gallons as the
first step of the troubleshooting process, and I know tank was fairly full
to start with.

Chris Bowne
Stonington, Ct

 

Check the fuel pump relay first, it's in behind the fusebox in the center
console of an '87 but I think by '90 they moved it, very common problem is a
cracked solder joint on the circuit board inside, the cover pops right off,
no need to replace it if you have a soldering iron, the fix takes only a
couple minutes.

 

The fuel rail should have pressure. The pump runs a couple seconds when you
first turn the switch on. The pressure should remain. Carefully loosen a
fitting with the switch off to check for pressure. Disconnect the Air Mass
meter and see if it starts. With the AMM disconnected it goes into "limp home"
mode. If it starts without the AMM it is either AMM wiring or the AMM. Check
the web for a better price than the dealer on new and rebuilt AMMs.
Check the brickboard for relay info.


Good Luck

Al

 

Had the same problem on a UK 740, changed the fuel pump relay (at the back
of the fuse box in the centre console on mine) fired up fine after.

Steve

 

Agreed with others. Replace the fuel pump relay first. Similar
problems happened on my 88 740 GLE. Changed a new relay ( located in
the centre, after the ash tray), and the problem was gone. Good luck.

 

Try checking the Main Computer Power Module. This cuts power to the
fuel pump(s) until all safeties check OK at the main CPU.

This might help.

Gustavo Suárez
1986 740 GLE w/ 267,000 miles and still going ...