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760 fuel problem helllllppppp

nickvolvo746

Member
Joined
Nov 13, 2017
Location
New Jersey
1991 760 Turbo lh2.4 AW71


Hey y'all, I'd love to re-pick some brains here.
Buzzing fuel relay.
Recently made a post here to ask for advice about a similar or the same problem. At the time, it was the case of me being an idiot and running the tank dry and frying a relay. Replaced relay fixed it but recently the same relay has been buzzing a little bit. Usually I jiggle it and unplug the computer and then Im back on the road. Today the jiggling did not do the trick. This leads me to believe that it is a wiring issue. In any case, I am posting because I am hoping to get some tips of where else to check for possible culprits of this no start. Kinda a noob so I just dont know all the pesky spots that might be hooked into the fuel system.

ALSO* I will try and get a picture of this tomorrow, but, the two fuse slots for the fuel pump and injectors are burnt out and without fuses in them and instead there are two spare slots with one wire coming from each. Perhaps that is where I should start?

Any help here greatly appreciated.
 
You got a volt/ohm meter? Start checking some continuities! You should get a wiring diagram to guide you. I could see running the tank dry burning up a fuel pump, but not a relay.

I'm no pro, but I would verify you are getting good voltage to (or through) the relay (check grounds).
 
You got a volt/ohm meter? Start checking some continuities! You should get a wiring diagram to guide you. I could see running the tank dry burning up a fuel pump, but not a relay.

I'm no pro, but I would verify you are getting good voltage to (or through) the relay (check grounds).

Will do. The pumps seem to be working ok, its just occasionally that it will crap out and no start, very puzzling
 
A buzzing relay would indicate a few different problems

Bad relay
Bad ground to relay coil
Bad power to relay coil
Problem with the ECU or whatever controls the relay

Some quick checks on the power distribution, battery cables and such.

Get a wiring diagram and have at it...
 
1991 760 Turbo lh2.4 AW71


Hey y'all, I'd love to re-pick some brains here.
Buzzing fuel relay.
Recently made a post here to ask for advice about a similar or the same problem. At the time, it was the case of me being an idiot and running the tank dry and frying a relay. Replaced relay fixed it but recently the same relay has been buzzing a little bit. Usually I jiggle it and unplug the computer and then Im back on the road. Today the jiggling did not do the trick. This leads me to believe that it is a wiring issue. In any case, I am posting because I am hoping to get some tips of where else to check for possible culprits of this no start. Kinda a noob so I just dont know all the pesky spots that might be hooked into the fuel system.

ALSO* I will try and get a picture of this tomorrow, but, the two fuse slots for the fuel pump and injectors are burnt out and without fuses in them and instead there are two spare slots with one wire coming from each. Perhaps that is where I should start?

Any help here greatly appreciated.

You sure it's a 1991 760? In 1991 there was a 940 SE.
 
1988 760 fuel pump replay buzzing was caused by bad connection at the boost pressure over-pressure switch. The wire from the LH 2.2 ECM on my car grounded the fuel pump relay. Bad connection of this switch caused the fuel pump relay to sound like a rattlesnake. Bypassed the boost pressure switch and the buzzing went away. So check the ground wire from the ECM to the fuel pump relay.
 
1988 760 fuel pump replay buzzing was caused by bad connection at the boost pressure over-pressure switch. The wire from the LH 2.2 ECM on my car grounded the fuel pump relay. Bad connection of this switch caused the fuel pump relay to sound like a rattlesnake. Bypassed the boost pressure switch and the buzzing went away. So check the ground wire from the ECM to the fuel pump relay.

Any idea where I can find the wiring diagram for a 1990?
 
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