87 760T Wagon Loss of Fuel Pump Control

Feb 23rd, 2005, 22:12

This problem was intially hard warm restart after running. The car would have to cool down thoroughly (up to 2 hours before restart). I installed a new Fuel Pump Relay, but no soap. I ran a diagnostic procedure which tested voltage between pin 13 and pin five of the ECU with the key on, harness connected and saw 12 volts. The normal values were from 5 to 0 volts depending on temperature. I don't know what the 12 volt reading means. Resistance measurements seemed normal considering the temperature. The problem has gotten worse!! Now I have no cold start or fuel pump when cranking. Additionally, if I jumper the correct relay sockets to provide 12 volts to the main pump, the pump runs, but the car will not run. Anyone know what the answer to this puzzle might be?

Feb 24th, 2005, 15:05

I had a very similar problem on my 86 760. My problem was a burnt connection where the wires go into the back of the fuel pump fuse in the fuse block. It would start after cooling off a couple hours. I clipped the wires and installed an in-line fuse holder. But if you have your 12 volts..........maybe its something different. Might be worth looking at............Good luck.........Vince I.

niloc · Feb 25th, 2005, 21:59

Pull the fuel pump relay and inspect both the relay and the holder for signs of excessive heat. A common problem is a bad connection that causes arcing. One of the tracks on the PCB fails as a result. You can either get a replacement relay (breaker's yard) or repair the existing one with wire soldered across the break in the track.

Mar 1st, 2005, 00:21

Okay, thanks for the posts! The problem was the Halls plug had come out of the distributor lip and was hanging down long enough that the black wire connection to the plug worked loose. I glued the Halls plug back into place w/the wire reconnected and I'm motoring again! Now can anyone out there tell me why the automatic transmission overdrive kicks down out of overdrive and won't go back into overdrive??

niloc · Mar 8th, 2005, 18:13

Change transmission fluid.
Check the overdrive wiring.
Check here: http://www.volvoclub.org.uk/faq/TransmissionAuto.html

Feb 23rd, 2005, 22:12	#1
Gibson Guest Location:	87 760T Wagon Loss of Fuel Pump Control This problem was intially hard warm restart after running. The car would have to cool down thoroughly (up to 2 hours before restart). I installed a new Fuel Pump Relay, but no soap. I ran a diagnostic procedure which tested voltage between pin 13 and pin five of the ECU with the key on, harness connected and saw 12 volts. The normal values were from 5 to 0 volts depending on temperature. I don't know what the 12 volt reading means. Resistance measurements seemed normal considering the temperature. The problem has gotten worse!! Now I have no cold start or fuel pump when cranking. Additionally, if I jumper the correct relay sockets to provide 12 volts to the main pump, the pump runs, but the car will not run. Anyone know what the answer to this puzzle might be?

Feb 24th, 2005, 15:05	#2
vray Guest Location:	RE: 87 760T Wagon Loss of Fuel Pump Control I had a very similar problem on my 86 760. My problem was a burnt connection where the wires go into the back of the fuel pump fuse in the fuse block. It would start after cooling off a couple hours. I clipped the wires and installed an in-line fuse holder. But if you have your 12 volts..........maybe its something different. Might be worth looking at............Good luck.........Vince I.

Feb 25th, 2005, 21:59	#3
niloc SWV Benefactor Last Online: Jan 30th, 2013 13:44 Join Date: Dec 2001 Location: Newport, South Wales	RE: 87 760T Wagon Loss of Fuel Pump Control Pull the fuel pump relay and inspect both the relay and the holder for signs of excessive heat. A common problem is a bad connection that causes arcing. One of the tracks on the PCB fails as a result. You can either get a replacement relay (breaker's yard) or repair the existing one with wire soldered across the break in the track. __________________ Refitting is the reverse of removal???.....Yeah, right!

Mar 1st, 2005, 00:21	#4
Gibson Guest Location:	RE: 87 760T Wagon Loss of Fuel Pump Control Okay, thanks for the posts! The problem was the Halls plug had come out of the distributor lip and was hanging down long enough that the black wire connection to the plug worked loose. I glued the Halls plug back into place w/the wire reconnected and I'm motoring again! Now can anyone out there tell me why the automatic transmission overdrive kicks down out of overdrive and won't go back into overdrive??

Mar 8th, 2005, 18:13	#5
niloc SWV Benefactor Last Online: Jan 30th, 2013 13:44 Join Date: Dec 2001 Location: Newport, South Wales	RE: 87 760T Wagon Loss of Fuel Pump Control Change transmission fluid. Check the overdrive wiring. Check here: http://www.volvoclub.org.uk/faq/TransmissionAuto.html __________________ Refitting is the reverse of removal???.....Yeah, right!

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