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Mercury Mariner 200 Magnum EFI

M

mtnpruitts

New member
I have lost the ground to my electric fuel pump. It is supplied from the EFI unit and is the #2 wire in the harness. I have tapped into the wire inside the unit to eliminate a bad connection or broken wire. Is the EFI unit bad or is it a sensor some where? If it is the unit itself, what went out?
Gary
 
Gary,

It is 90% the computer, Is the pump running with the key OFF. Those pumps get 12V applied to both + and -. then the ecu pulls to ground on one side and runs the pump. I have replaced two this year for the same problem. The first one I ever did like this, I spent 4 hours tearing apart the harness and looking for breaks etc when the ecu basically burnt threw the circuit board.
 
Thanks for your reply. Yes I have 12V on postive and negative side of pump. When you turn on the switch, the EFI unit is suppose to turn on ground to the negative side of pump to bring pressure up for cranking. It never applies a ground. I can manually ground the negative side of pump and the pump runs fine. I can actually crank the engine this way for a few seconds. There are a couple of places that rebuild the EFI for $600 to $700. But, I dont think they can fix it if it is the computer chip in the EFI.
Gary
 
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