Ford Repair: 95 Ford Explorer V6 Fuel/Relay Prob-Not Starting, fuel pressure gauge, inertia switch

Question
Hello and thanks for being here.  The problems began when it wouldn't start one afternoon.  The mechanic pounded on the fuel pump and it started.  The fuel pump was replaced and not too many weeks after that a similar problem when it would not start.  This time it sounded as if it weren't getting any gas.  Replaced relay and all was well for a couple weeks and now it won't start again and it sounds like its not getting any gas again as before with the relay.  When we talked to the mechanic again he indicated that there could be more than one relay not working.  We took new and currently working relays from another vehicle but no luck.
Have any suggestions?


Answer
Donnie, you really need to install a fuel pressure gauge to the fuel rail for testing... it could be that the pump is running but not producing adequate pressure - at least 30psi.  It could be that the new fuel pump is not running at all (I've seen many aftermarket pumps that don't work, or fail soon after installation).  
If the problem is 'no pressure', then use a test light or voltmeter and see if there is power to the pump.  You can start at the pump (has 4 wires on the connector - two smaller wires are for gauge, two heavier wires are for the pump (the black is ground, the color is power))
If accessing the pump connector on the left frame rail is difficult, check for power on the inertia switch (R side kickpanel, I think) and if that has power on both sides, you can be pretty confident the pump has power.
If there is no power at the pump, and no power at the inertia switch, then go back the relay...
It gets power from the EEC power relay, and although they look similar they are not interchangeable.  They also get their ground signals from the PCM, which only turns on the pump for about 2 seconds unless the PCM sees an ignition (RPM) signal.  So, you can see that the computer controlled functions need a trained technician with schematics to be able to determine where the fault lies.
Hope this helps...
Clay
(BTW - you may be able to get your local Ford dealer to copy a few pages from their wiring diagrams to help you locate the proper wires at the relays for testing)