Well, Its not the fuel pump | Ford Explorer Forums - Serious Explorations

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Well, Its not the fuel pump

greasemanicure

Well-Known Member
Joined
November 1, 2006
Messages
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City, State
Burlington, NC
Year, Model & Trim Level
1996 4X4 4R->5R mod
Last month I wrote of our 95 EX OHV coming to a stop in WV as though it ran out of gas. That time it was the plug on the inertial switch being kicked loose.

It has been intermittently refusing to start. Symptoms are no fuel pressure and a "lean bank" code. For no apparent reason it would eventually start. Today it did it again and I did some further diagnostics.

Fuel pump relay operating with no burnt contacts. Intertial switch normal with low contact resistance. Checked the voltage at the relay and it was near the battery voltage. Voltage at the inertial switch plug, however is down to 6.7 volts. Not near enough to run the pump and that is with the pump disconnected. I verified that the pump is OK by connecting a jumper from the battery to the pink lead on the inertial switch connector and the fuel pump ran and brought the fuel pressure up to normal. From the wiring diagram I have the only thing between the relay and the inertial switch is a lead from the controller. Is it possible that the engine controller is pulling the voltage down? I read on the forums that if the crank position signal is missing the controller would kill the fuel pump, and the only link it has to the fuel pump circuit that can drag the voltage down is the Pin 40 lead to the make contact on the fuel pump relay.

I know it sounds a bit out there from an electrical circuit view. The only other thing would have to be something between the fuel pump relay and the inertial switch. The circuit is almost too simple to fail this way.

Any thoughts?

Joe
 






I think that's what they say about the toyota system... :) The control system doesn't provide voltage to the fuel pump.... it only operates relays thru which contacts provide voltage to the fuel system. You have a poor connection some where IF you have measured the conditions correctly (which its appears is true)..... but your statement "with no burnt contacts" might not be "valid science"... measurements of voltage before and after is probably more useful.
 






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