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Fuel pump running after switching engine off.
Posted: Mon Apr 06, 2015 8:29 pm
by Metal
Title says it all, it seems like the red wire to the fuel pump relay is being held on by something which the manual says is the fuel pump prime connector but i have no idea what this is...
Re: Fuel pump running after switching engine off.
Posted: Fri Apr 17, 2015 8:18 pm
by bhm1712
the fuel pump relay has 5 wires going to it. 2 are for the coil, and 3 for the switch. (one common and 2 switched outputs)
The fuel pump prime connection is a 12 volt supply which runs through the normally closed contacts of the relay. when the relay is de-energised it gets a 12v signal from the ECM when you first turn the ignition on and sends it through these normally closed contacts to the pump. Once the engine is running the relay switches over and the pump is supplied from a different ecm output and via the oil pressure sender.
As you say the fault occurs when the engine is off, this points to the oil pressure sending unit switch being faulty. Once the engine is running and it detects oil pressure, the fuel pump is supplied through a switch from the oil pressure sender. This is how the fuel pump turns off in the event of a crash or similar which stops the engine from running and prevents (hopefully) the pump from spraying fuel everywhere. If this switch is not switching when the oil pressure drops to nothing, then it will continue to supply 12 volts to the fuel pump.
that's would be my first place check.