XJR standby Fuel Pump hack 
Tuesday, August 15, 2006, 01:41 AM
Theis feature applies only to the supercharged model XJRs from 1995-1997, which have a secondary fuel pump inside the tank that kicks in at 4000rpm and disengage at 3200rpm.

Shown below is the Secondary Fuel Pump control module which looks like a weatherproof black relay and fits into a relay socket on the left immediately below the tank itself, accessible by lifting the battery cover in the trunk.


The relay controleed by this Module is a blue one on the right immediately forward of the battery likewise below the tank.

In an emergency where the primary fuel pump has been positively diagnosed to have stopped working and you're stuck on the road in the middle of nowhere, an easy way to get home is to pull the black ECM out of its relay socket to prevent damage (and I would also recommend you yank the primary relay out of its socket, that'd be the blue relay second from the top right in the trunk fusebox), and hotwire the blue relay terminal on the rightmost side with the solid pink wire (shown separate and pulled over onto the right for clarity), to earth using one of the ground attachment studs on the body at the right side of the battery.

This can easily be done by likewise pulling the blue relay out of its socket, sticking a wire capable of around 10A load into the terminal of the socket (where the far right solid Pink wire surfaces) and inserting the relay sufficiently tightly to ensure contact with the terminal but not so far as to expand or break the terminal socket beyond repair.

This will cause the secondary fuel pump to run all the time the ignition is on, allowing you at least drive home or to the nearest Jag dealer.

Warning: Doing the above will probably trigger the Engine check light and may require substantial repairs.

Disclaimer:
Obviously if you blow yurself up, short out your Jag or otherwise inflict bodily or material damage to anyone or anything I am not responsible. You must ignore this information if you do not comprehend its meaning and the consequences of playing with gasoline and wires in your trunk. Your mileage may vary, especially if you spontaneously ignite your vehicle.