i recently had a problem with my Jaguar daimler XJ6. i had recently changed the fuel pump because the old one broke due to dirt inside it. well when i put the new one the car worked perfectly but then unfortunately the car switched of on the road so i had to tow it. i opened the fuel pump and checked if it was working. it actually was working if i plugged it directly to the battery but whenever i plug it to the actual supply where the fuel pump stays the car seems to not give power. what im trying to say is that the fuel pump stays somewhere in the back but the power supply doesnt supply power. i think its a fuse but i was also wondering if u could tell me where the fuse stays and what are your opinions to this.. by the way i checked the relay under the dashboard and its fine but still the pump doesnt run.
Here's some thoughts, but I don't claim to be an expert...
What year is your car?
Are you getting any dashboard warnings (the big exclamation mark)? Can't quite be sure of what you are saying... are you saying the pump doesn't run at all, eg, you cannot hear the pump run momentarily when you first turn on the ignition? (I'm assuming that is the symptom) ...Or are you saying the pump doesn't seem to be putting out a sufficient flow to keep the engine operating?
My Haynes manual shows the fuel pump relay as a brown relay beneath the passenger dash. A brown wire from the battery feeds it... check that brown wire for 12v (wire to ground) at the relay with a multimeter.
If you have power there, maybe the ignition switch is not switching the fuel pump relay on through the "ignition on" relay (blue) or the main relay (purple, I think).
The main relay should send battery power to operate the fuel pump relay via a white w/ brown trailer wire. I'd be tempted just to replace all three of those relays, but perhaps you can test them (easy for me to say, I don't have to do it... there's a procedure in the Haynes manual that (with the relay removed) consists of checking continuity between the switched "power" terminals while applying 12v through the control "energizing coil" terminals... the procedure is a bit too wordy for me to retype here).
The wiring diagram shows a straight shot from the FP relay to the fuel pump (blue wire w/ red tracer, then a black wire from the pump to chassis ground). Check the black wire (disco'd at the pump) resistance to a known chassis ground with a multimeter on the ohms scale (should be zero resistance). At the fuel pump, check the blue/red wire (while the ignition is being switched on) for 12volts across to a known good chassis ground during the first second after the ignition is switched on. If no power, check the same wire at the fuel pump relay end.
If the blue/red wire is not being powered, and you know the "ignition on", main, and fuel pump relays are good, and that there is power to the blue/red wire at the fuel pump relay, then it's a matter of determining where the power feed is broken....
If you didn't already replace the FP relay, try swapping it with another similar relay to eliminate it, ie, put a known working relay into the spot where the brown relay normally goes and check for power flowing out the blue/red wire. If you have power coming into and out of the FP relay, but no power at the pump, then you need to check for a bad harness connector on the harness that carries the blue/red wire.
Beyond that, if the fuel pump is not being powered, it seems to me that the ecu is seeing some problem and not allowing the FP relay to be switched on, hence my question about dashboard warnings.
Also check that all connections are clean and tight. Sometimes the female end of a connector gets spread slightly so that it does not make a reliable connection. This can cause much difficulty in finding the problem.
thanks for your email... umm....so do you mean there isnt a fuse for the fuel pump. the only thing like the fuse is the relay. the the fuel pump only has a relay???....no fuse.. there are no signs coming up in the dashboard sayin anything failing.
i will check my car with the answers you have given me and if i face trouble i will contact you again.
A bad fuse should give you a dashboard warning, I think.
The only fuses that looks like they might affect the fuel pump (indirectly): 1. in the fusebox located in the center console below the armrest lid, under a cover at the front... #8 fuse (3 amp) 2. in the fusebox in the left footwell, fuse A3
... but I'm certainly no expert, you're getting the advice you're paying for.
I had an 88 XJ6 that quit a couple of times and it was the relay located under the glove box. I changed it twice, and always kept a spare on hand. Finally it quit again and changing the relay did not help. Tracing the wires back to the pump, I found that if I ran a ground direct from the pump to the frame it ran fine. Somewhere in that circuit the ground was not working. I drove it for a long time with a jumper from the pump to the frame- when the motor finally expired at 250,000 miles I scrapped it.
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