95 XJS 4.0 fuel pump wiring - power - fixed

Pump has quit but before I pull it out I had a question. I have 12+ volts when I check across the blue and black wires on the plug on the top of the pump housing. There is no power when checked across the orange or brown nor any combination of those two wires with anything else. What do they do? Also, I am assuming that if I have the 12+v across the blue and black wires I should be hearing the pump run…correct?



The wiring diagram says a blue/red wire provides power and black provides ground to the pump. Not sure about other wires.


Welcome in the landonof confusion, Bill.

I assume that you’re checking fuel gauge’s sender wires, hence no power. I also hope you’re alive/haven’t tried to power the remaining two up with battery…

funny on the Blue/Red and Black wires. There is no red tracer or otherwise on the solid blue wire. I found out after I got the pump out that there are only 2 wires servicing the pump (blue and black). So I have no clue what the orange and brown wires are. I don’t even find them on the schematics as well. There are brown and green/red tracer wires on the sending unit (replacing that was well since its been flakey anyway). Agreed XJsBanger on the “land of confusion”…


Jaguar was employing color-blind people, hence the confusion. They could do nothing about it due to potential union’s industrial action. Positive wire goes from brown into blue and then later on, when Jaguar expanded it’s palette - into red. Thanks to the same color-blind people - British Racing-Green was invented.


I’m color blind for red/green. Have not had a single problem tracing wires in my Jag.

now a power question - I have 3.5 volts at the pump. I have bypassed the pump relay (jumper) and all upstream fuses are good. I would assume the 3.5 volts is backfeed voltage from somewhere else. What am I missing? I had 12.5 (weak battery) prior to removal of the pump

continuation - cleaned the grounds next to the main body ground in the trunk. Voltage jumped up to 5.5 volts. But then something very curious was observed. As I held the meter probes to the pins in the fuel pump plug, the voltage continued to rise. Slowly, but over about 30 seconds rose to 9.7 volts. What the heck!!!

That connector has a habit of getting overloaded and melting.
Sometimes it doesn’t appear as a defect and needs to be checked closely.
Measure the voltage after the large connector nearer to the tank.
If you find an issue there clip both sides of the connector and replace.

not melted, but was the white connector at the right side of the tank where the wires run from the relay around the trunk lid support and connect to the pump harness. I happened to bump it and the pump started. Unplugged it and replugged it, everything now works so must have been a dirty connection.