Jaguar Repair: Fuel Pump Relay Nightmare, jaguar vanden plas, 1998 jaguar vanden plas

Question
QUESTION: 1998 jaguar vanden plas : 4.0 : 57,000 miles : replaced head gaskets : timing chain/tensioner/water pump/thermostat upgrade

I know this car well. I restore antique British cars, so Im not a novice when it comes to turning wrenches. This problem has me completely stumped and is on the verge of retiring my car permanently. I had a fuel pump die so I pulled the tank and replaced it. Now, the only way I can get the car to start is to pull the fuel pump relay and use a wire with two spade connectors to energize the pump. This works half the time. Many times I can hear the pump running after installing the jumper wire but still have 0 pressure at the rail. The car will not run with a relay installed in the fuel pump relay spot. Put a jumper wire in the two terminals and within a few tries she's running perfectly. What am I missing? I'm so confused and frustrated. Every time I want to use the car I have to open the trunk install the wire. Open the hood check for pressure, go back and forth a few times till I can close both and get in and go. At that point, I don't want to turn it off bc this starts all over again. Please help!

ANSWER: First lets make sure you have a good relay. Apply 12 volts to the coil of the relay and see if the contacts close. If you have a good relay, check to see if there is a fuse in the fuel pump relay line. Check to see if there is 12 volts at the coil contacts on the relay socket when you turn the key to the on position. If there is not 12 volts at the relay contacts, check the following, on/off switch,fuses, wiring and fusible links. I hope that this helps. Sam

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QUESTION: Done all of that. Any other advice?

Answer
Was there 12 volts at the coil? If so, did the relay contacts close? If you have 12 volts at the coil and the contacts closes then the fuel pump should run. If it does not then you have a bad fuel pump, fuel filter, fuel pressure regulator or bad connection some where. Also replace the relay and see if that works. I hope that this helps. Sam