I changed over my fuel pumps as I think I had one bad one and no need to replace one and then be doing that job again! As I was diagnosing the problem I found a home made jumper that a previous owner (or mechanic) had used to wrap around the ground tab on the 2 fuel pump relays the other end of the jumper was connected to the screw that secures the relay box to the trunk floor (ground). I found the jumper right away and pulled it out but found the car will not run without it. I haven't taken it out since replacing the fuel pumps as I can't see what purpose it could serve other than to give the connectors a little more bite on the relay ground tabs. Are these boxes a little weak in the connector area? Is this likely as simple as pulling the box and giving the connectors a little squeeze? Has anyone else run into something like this? I can see if the connectors didn't grab the tabs firmly you could have all sorts of intermittent problems. As Jaguar sprinkled relays all over the car this would have the potential to be a huge issue. If it really is an issue I've got to believe someone else has run into it.

 

Normally the ECM will add 'EARTH' (ground) to activate a relay. Ve (positive) is usually 'hot all the time' or KEY-ON for the other side of the coil.

Perhaps the ECM ground activate circuit is faulty and the pump relay circuit was 'modified'????

You need to look at the electrical guide to determine how it was 'modified'.

bob gauff

 

wahooooooooooooooo!
I have a feeling (after only a month of Jaguar ownership) that this is going to be a roller coaster experience but I pulled the jumper, added a coating of solder to each spade on both fuel pump relays, plugged them in, and am back to "unrestricted performance".
No there's no message that says that it's only implied when you blow by the morning rush hour crowd at 90 (mph).
I'm a mechanical engineer so the intricacies of pulling relays to ground tend to make me gloss over but poor contacts are easy to understand and appreciate.
I think the first step on any electrical issue I chase down on this car will be to see if there's a relay and then give it the same treatment.
Chasing down a flaky contact has got to be one of the most frustrating jobs any shade tree mechanic can face (IMHO).
Anyways, case solved, pheeeeeew!

 

it is. especially when someone gets in there and fiddles with it and turn it into a rat nest of poor connections.