I have been chasing a problem with my 1994 XJ40. The car only starts after extreme prolonged cranking (battery dies, so I have to jump-crank to get it to start). Once started, it runs great!

I have replaced the crankshaft position sensor and the fuel pressure regulator. I am told that the check valve inside the gas tank could be the problem but this part is no longer available for sale.

Any thoughts?

Thanks in advance,

Dave

 

I would check to see if you had fuel pressure as soon as you start cranking! there should be a shrader valve on the fuel rail kinda looks like a tire valve. You should around 45psi as soon as you turn the ignition. If not then the gas is probably draining back into the tank or the pump is bad? If you have good fuel pressure it has to be the spark. Hope this helps or at least gets you closer to starting the car. Paul

 

Welcome to the forum. If you haven't done so, please go introduce yourself in the new member section.
You will need a fuel pressure gauge to troubleshoot your issue. Get yourself the Haynes Repair manual 89-94 XJ6 as well. After posting 10 times here you can use all of the features on the forum and resolve your problem(s)
Your fuel pump is in the trunk. You need to check the fuel pressure while cranking the engine. Just because there may be fuel, doesn't mean its the right fuel pressure. The good news is that it starts.

 

Dave:
Sounds like the guys are sniffing out a fuel pressure problem, very likely quite rightly. The only thing I would add if you have not tried it already, is before starting the car try the "key cycling trick" - that is, slowly turn the key through positions I and II without starting the car, and then back again. Go through the cycle four times or so and see what happens. Theoretically, each time there should be a priming burst, ensuring plenty of fuel at ignition. If this works, it would seem to further indicate a fuel pressure problem at start up.

If your fuel pump is failing, alas, it will be a bit of a spendy job seeing as how the pump is in the tank and the tank will need to come out for replacement.

Cheers!
Scott

 

I have a similar issue and can't find a shraeder valve anywhere on my '93 XJ6 so that I can check fuel pressure. Can someone tell me specifically where it is or if it is really there? If not, where is the best place to check fuel pressure?

 

I would change the fuel filter and then while you're down there check the pressure at that point.

 

The haynes manual doesn't mention a shraeder valve on the rail. The manual says to remove the fuel line from the fuel pulsation damper install a tee between the damper and the fuel rail and that gives you an access for the guage. Make sure you depressurize the system before you open up that line . Hopefully someone that has done it can verify this is the correct way to check the pressure.

 

As the fitting are not the same as most cars use you will have to make an adapter to fit a pressue gauge. You can get a tee fitting and some threaded brass from most hardware stores. The pipe should be about 3 in long. You will also need an old fuel rail with the hose from the inlet side,(i got one from a pick a part salvage yard). Then cut the inlet fitting off the fuel rail (make it as long as possible) then cut the exit fitting off the fuel valve which is attached to the hose. Then cut the brass pipe in half.then braze the fittings to the pipe halfs(not on the threaded ends). Screw the fittings into the tee then check to make sure you have no leaks. Once this is done all you need is a pressure gauge and as your tee fitting is universal plumbing parts it will adapt to any pressure gauge. I did this as i couldent find any one with a test kit with fittings that would fit my jag.

 

FWIW, my '88 XJ40 would not start for a couple days after it rained. Crank and crank but no fire. Put in a new dist cap and rotor, only rained once since but it started fine. Not ready to declare it fixed, but definetaly seems better.
(double posted from "fuel or no fuel" thread)