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problem whit fuel pump always on key off ? need help or schematic

T

tybob

Member
hi , my fuel pump is always on cause me a heads gasket failure 2 week ago , i change my fuel pump for a new walbro and get the harness too , i also change my injector for a new set of 42 .

when i plug my batteries back i still have my new fuel pump run all time whit out the key . i unplug all the relays and the pump still run , i change the chip too and still run ?

so i think maybe the 12v wiring is short to a live 12v somewhere DontKnow:

somebody have this trouble before ? somebody have a fuel pump schematic ? that can help to find my trouble .

thanks guys
 
Check all wires going to oil pressure switch for cuts, fray etc., its grounded somewhere, was it doing that before you changed pump and hotwire ?
 
My guess is bad wiring to the oil pressure switch or the switch itself is bad, but i never seen one do that with the key off.
 
hi , i make the test , when i unplug the oil pressure sensor the pump stop . so maybe oil pressure is bad :) thank guys i let you know when i got it change :)
 
^^^ Good news! :thumbup:

Can anyone explain why having a bad oil pressure switch would make the fuel pump stay on? DontKnow: (simple curiosity)
 
I believe that the OP switch is designed and tied together with the FP so when it detects OP while cranking, it sends/tell the FP to run. Without OP, it won't let the relay tell the FP to run and then you have a NO START condition.

Now I have NO idea why his ran with the KEY OFF. DontKnow:
 
the only way to shout dow the fp war unplug my orange wire near the batterie before ... but now its fixe :D
 
The way it works is that the fuel pump can get power in two ways:

1 via the fuel pump relay; this requires key on

2 via the oilpressure switch (when pressure is high enoug)

(and actually a 3rd way which is via the diagnostic connection port - fuel prime which bypasses 2 above)

So why 2 ... well if the fuel pump relay dies when you are out driving that would be no good this takes care of that issue ... also helps when you turn off the engine and quickly tries to turn it back on again with enough oil pressure the fuel pump is primed and ready to go.

2 is a direct feed from the battery hence the fuel pump running even if key is off


I think I covered all aspects there :-)
 
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