Fuel Pump low voltage?

[bankbadhabits]

I have a '92 EB 4.0 that completely died on me while driving. I have tried many, though not all the electrical checks ( not all the individual pin checks yet ), new relay etc. Have the no pump noise problem.

When checking voltage at the pump connector I have 7.75 volts at one spot, 6.5 at another of the 4 pin connector. I have read about battery voltage and no voltage but not lower values. Or am I just being really stupid about how I'm reading this? If so, sorry, I already feel that way.

 

[Diff Whack Daddy]

Some of those wires are for your fuel level sender which would have a lower voltage depending on the level of fuel in your tank.

 

[JTX]

I went through the same problem, just ended up wiring the pump to a switch. I believe mine had a short somewhere along the way to. Even if it has 12 volts to the pump doesnt mean its good. If there isnt enough amps the pump wont work either.

 

[DeRocha]

No need to feel stupid... As you may already know the fuel pump will only run when given 12v... When you turn the key from run to start the inertia switch (pictured below) will see 12v for only 2 secs or while the tac registers > 0 RPM. After 2 secs of zero RPM the computer will shut off the fuel pump relay and you'll only see ~7v at the inertia switch and fuel pump. Seeing 7v is weird but that is what you'll get if you check the wiring. Anyway check out/search threads such as Fuel pump not working for more info...

 

[billk86]

I'm having the same problem with a 93 explorer Eddie Bauer edition. I even bipassed the inertia switch. I still can't figure it out

 

[MrShorty]

billk86: I don't know how thoroughly you have tested your fuel pump circuit. I would suggest, as a systematic way to approach the circuit, is to start at the battery and measure voltages at convenient places along the fuel pump circuit (battery, fuse, relay, inertia switch, pump connector. a wiring diagram will be helpful -- even the one in Chilton's will help). Your voltages will generally either be 12 V or 6-7 V. Your circuit problem will be between the last place where you had 12 V and the point where you have 6-7 V. Once we know where that is, we can diagnose further.