Franz

My daughter drives our '91 XJ w 4.0L and AT and it died a few weeks back just a minute after leaving the driveway. I suspected the fuel pump as it required some extra cranking time to start in the last 3-6 months. I jumped the fuel pump relay with a paper clip and it did not run the fuel pump so I figured the relay is OK.. Bought a new Precision fuel pump and filter from O'reillys and installed last weekend. I have not heard the new fuel pump run at all when turning key to run position. I swapped relays in the PDC - the fuel pump relay and I believe the adjacent relay which is the same relay number, no improvement.I double checked the new fuel filter direction and it is correct.

I have 6 volts in two of the three wires within the connector leading to the fuel pump module while using the third as a ground. This sounds correct from some posts I have read here. One serves the pump itself and the other the fuel gauge is my assumption. I removed the new fuel pump module yesterday and probed the pins on the tank side of the module - 6 volts on two pins. Interestingly, the gas gauge functions with movement of the float mechanism but there is no voltage at the red wire where it connects to the new fuel pump - this doesn't make any sense to me.

Side note - I could not reinstall the new module as it was too long. I had to shorten the fuel hoses in the new module in order to reduce the overall length of the module to get the module to sit in the correct position to allow for re-installation. Part of this process included disconnecting the red and black wires from their terminals and re-securing them after re-positioning the shortened hoses. I believe I put them back in the correct position. Regardless, I took these wires off their terminating screw connections to probe for power but found none.

So, the engine will crank, I have 6 volts in the three wire connector outside the tank, 6 volts at the module wiring connector pins inside the tank but no power at the new pump (red wire) itself. I brought the new pump module to the battery and connected it to the red and black terminals on the new pump - the pump ran immediately. I checked the ground wire behind the rear cargo area driver's side panel and it was shiny - I read this is a ground for the fuel pump. I checked continuity from the fuel pump ground terminal to the truck frame and it was good. I'm guessing not getting the 12 volts needed to initiate and prime the pump is my problem(?). I'm not sure what else to check.

Is 6 volts correct at the fuel pump power wire at the module or should it be 12 volts? If 12 volts for how long?
Is 6 volts correct at the second power wire which I assume powers the gauge/float mechanism?
I have heard other common failures are crank position sensor, cam position sensor(?), and something called the ADS relay. I swapped positions of the common relays (fuel pump, ADS, AC) but no change yet.

Any suggestions are appreciated.

Thanks,
Franz