Ran fine when put into storage. Installed new battery, now cranks but won't fire. Tried moving (switching) the fuel pump relay #6 with the rear defroster relay #2 and no difference. Checked for voltage at fuse #7 (20 amp) but show no voltage on either side of that fuse.


Fuse 7 mentioned above was something someone said to check, I don't even know if it's related to fuel system.

Also online someone said battery must be at least 850 cold cranking amps or these XJ8's won't start! Any truth to that? One I bought is only 825 CCA.

Last there is supposed to be a fuel inertia switch that I can reset...but I can't locate it.

Thanks!

 

Check the drivers handbook, the inertia switch is inside the passenger foot well.

 

Thanks! That might solve one mystery. I'm starting to think it's prob a bad fuel pump. If so, is that a big job on this car?

 

If the car cranks strong, forget the battery rating. The X-308 has a fuel test port. That would be your next test point.

 

Thanks guys! So next best thing to do is buy a fuel pressure tester and attach it to the valve on the passenger side fuel rail? Ball park of how much pressure I should have? If I have no (or minimal) pressure how can a person know that the fuel pump is getting voltage? Looks like there would be a test point where you could connect a meter and feel sure problem isn't electrical. I'm assuming the pump is inside the tank?

 

So, short answers- yes,40psi,test at the tank connector,no- but check at the fuel pump relay, yes

 

Sparkenzap, Thanks! Love the short answers!

 

New info guys. Don't think I need to buy a fuel pressure gauge because when I depress valve on passenger side fuel rail gas only comes up about 1/2 inch, then later when I checked it again none really came out!


Then I found the white connector at fuel pump and pulled it. Found approx. 10.5 volts DC on the two smaller wires (out of four total) a orange w white stripe and a black w white stripe. That's with key in "run" position.

Didn't see any sign of voltage on the two heavier gauge wires.

Anyway I've decided it's the pump. Tank has two straps holding it in, then almost looks like it would tilt down to change the fuel pump. Am I right? Or do you have to pivot the passenger side toward back of car because the filler neck won't allow it to "tilt"?

 

If relay is bypassed with jumper wire, does that eliminate all the other things that can impede fuel pump from working? In other words with a jumper in place (and assuming no open wires from there up to pump connector) if pump still doesn't work it HAS to be bad fuel pump?

 

It is ALWAYS dangerous to speak in absolutes. But, no, the voltage supply and the ground to the pump must both be OK to rule out something besides the pump. Use a meter on the tank connections.

And, in reply to your previous post: Although I have seen at least one person claim to have changed the pump without removing the tank fom the car, I know of at least two who have admitted to buggaring the fuel lines to the bottom of the tank while attempting to do so. Make your own choice, but I would remove the tank.

 

See on a previous post where I checked voltage at connector. Found approx. 10 1/2 volts DC on the two smaller gauge wires when the key was on. However I don't know if 10 1/2 vdc is normal? Also thought it strange that I read nothing on the two heavier gauge wires!?

 

Sorry, I missed that- First, the "big wires" will only have voltage when the pump is supposed to run. According to some documentation I have, the pump runs for a few seconds as the key is switched to the "run" position, then it stops until the car is "starting". However, on my MY99 XJR, the pump runs for a few seconds after moving the key to "start", not run. I do not know if "starting" is identified as key in "start position" OR if it is when feedback comes from the CKPS. In any case, the pump is not energized if you leave the key on, and not in start.

Now, you have apparently learned how to jump the relay, so assuming the relay is jumped, and the key is at "run", then you should have voltage at the pump terminals, and pressure at the test port.

The small wires are the fuel level. 10.2 volts would seem to indicate you are near empty!

 

Good info, that helps. Now I know I need another person to help me, by turning the key to "start" while I monitor the two larger wires for voltage. No one yet has told me what voltage should be there, but I assume I'm looking for 12 volts DC.

quote-
"Now, you have apparently learned how to jump the relay, so assuming the relay is jumped, and the key is at "run", then you should have voltage at the pump terminals, and pressure at the test port. "

So if I'm thinking about this right, if I was working on this alone, and I put a jumper across the #3 and #5 terminals of the fuel pump relay and had the key at "run" I could check for the voltage at the bigger wires without someone to turn key to "start" position? And I would have pressure at test port... IF the pump were good.

Also I have about 10.5vdc at small wires but show about 3/4 tank of gas.

Thanks very much for any info you can give me, I really appreciate it!!!

 

See if any of this information helps.

Link JagRepair.com - Jaguar Repair Information Resource

 

Yes, if you have power on the big wires, and no fule pressure, you can pretty much bet the pump, the wiring in the tank, or a hose blown loose in the tank are to blame. In any case, out comes the tank!
And, please note. I was wrong; I checked my XJR and found that the pump DOES NOT run, even for a few seconds, until the key is turned to "start".

 

Thanks Gus & Ross!!