I just purchased 94 XJ12 knowing the vehicle won't stay running. This is my 1st Jag. I was a mechanic for 20 years but mostly domestic. I'm in a new ball park now. The prev owner was told it was the fuel pump. The problem I have is that I'm not sure if that is the cause. Car starts right up after about 5 minutes starts to die down, I try to throttle it and sometimes it will continue to run other times cuts right out. Just as fast as it shuts off I can restart it just as fast but I go through that whole cycle again. Other than the enjoyment of detailing I replaced the fuel filter only. Has anyone had a simliar problem? I am kind of leaning towards a restricted exhaust. Any help would be much appreciated

Submitted by jdiadanza@comc… on Tue, 06/12/2007 - 19:27

Bob, Thanks for your input The fuel filter I replaced today fuuny thing is that with in the few minutes its running fine I start to hear exhaust type leaking noise as if its back pressure escaping. I'm not certain but I think these vehicles have 2 fuel pumps? if so it would be a costly venture. The restricted exhaust could give me a false fuel pressure reading. Your thoughts on the coil of course there is 2 but I thought I read somewhere that the vehicle will still run on 6 cylinders not recommended of course but do you know if this is true? Does anyone know if the o2 sensors are before the cats?

Submitted by jdiadanza@comc… on Tue, 06/12/2007 - 19:26

Bob, Thanks for your input The fuel filter I replaced today fuuny thing is that with in the few minutes its running fine I start to hear exhaust type leaking noise as if its back pressure escaping. I'm not certain but I think these vehicles have 2 fuel pumps? if so it would be a costly venture. The restricted exhaust could give me a false fuel pressure reading. Your thoughts on the coil of course there is 2 but I thought I read somewhere that the vehicle will still run on 6 cylinders not recommended of course but do you know if this is true? Does anyone know if the o2 sensors are before the cats?

Submitted by peddlarbob@sym… on Tue, 06/12/2007 - 18:54

Could very well be the fuel pump but the only way to be sure is to install a pressure gauge in the supply fuel line and check the pressure when the engine is running. If the pressure falls below 38PSI it is either the pump or the filter restricting the flow. My next choice would be the coil.
A blocked exhaust would be very apparent by prevent the engine from revving very high.

Bob.
92 Ser III V-12 VDP #31 Canadian Edition
87 Ser III V-12 VDP
86 Ser III AJ6/Soveriegn