Fuel pump voltage ?

I'm currently working on my bro-in-law's 1996 XJ with the 4.0 and AW4. It died on his wifes way home from work. First, i checked the fuel pressure at the rail while cranking and found zero lbs. Next, i pulled the fuel hose going to filter and gas wouldn't flow while cranking the motor. I disconnected the plug going to the pump and check voltage at the pins and found 5 volts at one or two of the pins. For comparison i checked the voltage at the same plug on my 2001 XJ and found 11 volts. I know that the pumps are different between the two models, but does anyone know if 5 volts is correct for a 1996? TIA blaise

5 volts ain't right. you need to have somewhere around 12 volts to make the pump function.

blaisetd said:

I'm currently working on my bro-in-law's 1996 XJ with the 4.0 and AW4. It died on his wifes way home from work. First, i checked the fuel pressure at the rail while cranking and found zero lbs. Next, i pulled the fuel hose going to filter and gas wouldn't flow while cranking the motor. I disconnected the plug going to the pump and check voltage at the pins and found 5 volts at one or two of the pins. For comparison i checked the voltage at the same plug on my 2001 XJ and found 11 volts. I know that the pumps are different between the two models, but does anyone know if 5 volts is correct for a 1996? TIA blaise

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Find out if you have spark. Though it will try to prime for a second or two every time you try to start, the fuel relay isn't going to close unless you get a pulse from the CPS. My 96 tries to prime and it really doesn't amount to much, a tiny squirt and trickle at the fuel rail.
Where did you ground when you tested voltage to the pump, my most common mistake is trying to test to a poor ground. If it was the pump ground, do an ohm test.
If you are sure your voltage test is good (you'll only have voltage for a second or two when the key is first turned to run) and you are sure your CPS is good because you have spark, try swapping the fuel pump relay with another relay out of your PDC (best something non critical).
Unless the CPS is pulsing, the fuel pump relay isn't going to close any more than a second or two when the key is first turned to run or start.

Fixed:
I checked for spark and it was there. I swapped the relays in the PDC around, but still no start/fuel. I didn't recheck the voltage. I didn't find the ballast either although I’ve seen it on my ‘90. Installed new fuel pump and screen and it started right up. I didn’t drop the tank, but did siphon some out and saw nothing but clean gas and no floaters. The hesitation/cutting out at full throttle is gone too. Thanks for the help blaise