Originally Posted by
PaulT1972
yes i just got done putting a new fuel pump in ... and at roll over switch loc. at the passanger front kick panel i get power there but pump isn't comming on so guess i need to check resistance at ground and power at the other wire see where i am losing a connection. not sure if roll over switch is last shut off to fuel pump on the 2k ford explorer sport with 4.0lt eng. if it is then there has to be a ground / hot wire break but can't find a wiring diagram online to see if ground might be on a relay or controlled by the pcm
well just checked my ground has no resistance so looks like it's going to be a ground problem but don't want to just ground it to the frame unless i know it's not controlled by the pcm
First, 12V should be present to GROUND on BOTH terminals of the inertia switch, but ONLY when the PCM is calling for the pump to be running-- therefore, if the engine cannot start, there will be voltage present at the inertia switch for only about 2 seconds, as the ignition switch is turned "ON", then the PCM shuts off the fuel pump relay, which in turn shuts off the power flow to the inertia switch and pump. In other words, you need to have your voltmeter hooked up, accessible, and readable when the key is turned to "ON"-- you only get 2 seconds of "PUMP ON".
If you want to overcome this 2 second problem, what I do is remove the Fuel Pump Relay, look at it's diagram showing the contacts inside, usually on the side of the relay, the 2 contacts shown as "Normally Open" (no slash mark through them) can be substituted for by a short piece of appropriate-sized wire inserted into the relay socket in the relay box. IF YOU DO THIS, BE SURE YOU JUMPER THE CORRECT TWO HOLES IN THE RELAY SOCKET! While jumpered thusly, when the key is turned "ON", the fuel pump will "think" the PCM did it, and should run, assuming the inertia switch is CLOSED. I would check for voltage between the 2 wires feeding the pump, right at the tank, in the removed harness connector. If 12V is present there, the trouble lies between that point and the pump itself.
Anxious to hear what you find!.. impish