Um, simply removing the relay will NOT do that. You will need to jump 2 terminals inside the socket for that relay, and I DO NOT know which 2.

My GUESS?????, is that a test light will identify which socket is LIVE with ign ON, and then simply find which one feeds the pump, that is the 2 you need.

On my XJ-S that is terminal 85 and 87, but I am not sure if you have the same codes???.

 

I will be working on this issue today. Troubling not to hear that whine at the fuel pump when I turn the key, although I have power to the pump, which works.

 

Thinking about it a little bit it kind of sounds like you might have a short somewhere. If you get voltage for just a split second and then it cuts out. Sounds like when you turn the key it tries to run and shorts out right away.

I would start with checking the relay as Grant said. I don't have my Haynes handy but it has electrical diagrams that are fairly descriptive. Also if you look at the relay there is a diagram on the top(usually) that will describe the relays functionality. A quick google search will tell you how to read them.

You can deduce which terminals on the relay are for power etc from there. Then I would test the relay terminal and see if you have the cutting out issue there as well. If it is cutting out in one of the sockets that supplies power to the pump then I would wonder if you had a short somewhere in the electrical system.

If the power that is used to switch the relay is not on then you may have an ecu problem as Grant said.

"The ECU controls the pump via the pump relay and activates it for about 1 second at switch-on to pressurise the system. The trigger signals then reactivate the pump to keep it running continuously whilst the engine is turning over or running. If the engine stalls the pump will be switched off after 1 second or so for safety reasons."

So I would try to jump the fuel pump power at the relay terminal and see what that does. If the pumps run and the car runs fine for a while then I would guess you have something going on (ecu?) that is preventing the relay from switching on the pump. Fuse box power checks would be a good check as well.

 

Thanks Gunner. The issue was that the fuel pumped was seized. The voltage in a spurt sent to that pump is normal, in which I had had tested with the leads off the pump. I had to get creative and use long wires from the leads to my volt meter, so that I could take the reading while turning the key. It had 12 volts every time I turned that key. I had then taken the next step in going through all of the tests from a 22 code. Not fun. I finally called a friend to come over, he got under the car and put his hand on the fuel pump while I turned the key and bingo, problem found. The pump wouldn't budge. The car is running again. BUT, there is an electrical issue within this car and I am stumped to find it. But that is for another thread.

 

BLOODY GOOD DIAGNOSIS MY MAN. Thats what mates are for, send them for the dirty work, bribe them with alcohol AFTER the task, you are a smart Jag owner.

What do you mean "electrical issues" with an XJ40, how odd haha. Thats why I divorced my '88, drove me nuts, dont miss that thing for one second, SORRY guys who luv '40's, I dont.

 

Glad to hear you found the issue. Also glad it is not some rats nest of a problem.

Kind of interesting.
My friend owns one of those Merstakes 1989 560sl's and one of the fuel pumps was leaking fuel around the casing. So I replaced the pump for him. Not 1000 miles later another leak sprung up and his friends said that it was from the same casing on the new pump again. He chaulked it up to a cheap pump and went and bought a new ~$250 dollar pump.

I went over there and he had already half installed the new pump when I got there and so I completed the reassembly. Upon starting it up I saw it was leaking from one of the copper washers on the other pump.

I took his 'bad' pump and bench tested it. No leaks.

His problem was a copper washer.