I have a 1993 XJS convertible with the 4.0L engine. It starts just great but after an hour, on the road or anywhere, she shuts off. The temp is fine; it has gas; battery is new; ABS light is on. Help, please.

Does it begin to lose power, just shut down as if you turned the key, anything different? Can you immediately restart it or does it take a certain amount of time?

The "cat" runs fine and after 1 hour just shuts down with no warning, she just quits. I can start it back up but it dies. If left for a while to cool down, she runs till she gets to the 1 hour mark and she dies. I was told that because my ABS light is on that the ABS system has a safety built in which kills the car at the 1 hour mark. Personally I do not give that thought much credit. I am thinking it is a cooling sensor of some sort, but I am not familiar with the 6 cylinder Jags as my expertise runs to the 12 cylinder (what humble expertise I do have). Thanks!

I don't know anything about the 6 in particular. Sounds like something overheating obviously. Wouldn't think it is vapor lock because it doesn't take that long to cool back down.
I guess it is possible, Jaguar can sometimes be weird, but I have never heard of a 1 hour ABS switch. So its safe to drive for an hour without ABS? lol, just sounds wrong to me, probably just a dirty/bad abs sensor.

Finding overheating parts is pretty difficult, at least the V12 has the obvious Amp overheating issue.
Just look at all the systems that can overheat and try to start diagnosing those. For example, after it shuts down, can you hear the fuel pump come on and prime? If not it is overheating and seizing. Hopefully someone will pop up with a bit more experience with the 6 or clues as to what this could be, but for now it all you can do is investigate whether different parts are working properly after it has shut down.

My V12 runs for about an hour and then it stops unless I fill it up again!
Seriously though, have you checked the fuel tank vents? If they are blocked it is possible that the pump will pull a vacuum which can be enough to stop the pump, er, pumping.

Steve, That is one thing I never thought about and that could be it. I am going to replace the coolant temperature sensor and the crankshaft position sensor since they are the originals. I will get into the "boot" and do a check on the venting. Thanks again.
Schoe

Next time your car stops, get out and open the gas cap to see if the tank went into a vacuum.

Hi , I saw your post about the car dying while creeping theforums. I have had the same experience with my 4.0 VDP. Have it put on acomputer at the dealer and still they couldn’t figure it out, and then someoneon this forum suggested it was bad ignition coils…………I know that’s crazy. I hada couple months earlier replace a couple coil packs with aftermarket parts andas the engine got hot the insulation in the coils would break down and thecoils would discharge into the valve cover. This would cause a large over loadto the cars computers and they would shut down (to save themselves fromoverload) killing the engine. Once the car cooled for some time I could startthe car like nothing ever happened, then in 45-60 min dead again.

Also just before the car would die the instrument clusterwould flash all warning lights.
If you search (instrument cluster flashing) or something like that in the last 2 years you may find the original post.

Thanks Gunner, It would be a great idea but... the 93 XJS 4.0L only had one primary coil. You do give me an idea about replacing the coil just in case. Coils do not cost much so I will give it a try. Thanks again.
Schoe

Oh darn! I've never been under the hood of a XJS, but maybe soon, I'm shopping for one this summer.
Good luck!

+1. If it's not that, find out if you've got a spark.

After it shuts off, without any warning, if left for about 15 to 20 minutes or so, it will start up and run fine for a while and then start the whole sequence starts again. After I pull the coolant sensor, the crankshaft position sensor and perhaps the coil, I should be able to give a report on what was going on. It also, as one of our esteemed colleagues has postulated or hypothesized, could be a plugged fuel tank vent causing vacuum in the tank which would cause all of the problems I have been incurring. Thanks all! I will let you know how it goes over the weekend as I put the "cat" through its paces.

My 92 XJ12, 45,000 miles, will run fine, but builds terrific pressure INSIDE the tank. When I open the tank cap a huge rush of vapor/gas comes gushing out. That was the first, and unsolved, problem. Now, I was driving on a hot day for about four hours and the engine just shut down. I could start it immediately and it would run for about a minute then it shut down. The longer I waited the longer it would run...for a while. It finally got so that it would only run for about a minute at most. (Being in the middle of Wyoming was a problem here).
I had someone check the fuel pump pressure and he said it was at 28 psi and should have been at 36. I also looked around the inter net and found there is a fuel cut off sensor. Seems like it is the pump or the mysterious fuel cut off sensor. I thought maybe about a vapor lock in the fuel delivery galleries above the engine, but the engine just shuts completely down, not just one bank of cylinders.
Any thoughts before I just start replacing things?

Hi, have had this on a couple of cars in the past (Triumph tr4a and Morris Minor)and its been the ignition coil overheating and so breaking down , leave to cool and all's well until it gets to the critical temperature , if nothing else its an easy one to test with a replacement coil .
We all tend to assume its something complex on more modern cars like our XJSs but having fooled around with old classics in the past its often something quite basic .
Good luck .

Well, I changed the fuel pump, the fuel filter (lots of junk in the tank, rust etc, from having sat for so many years with very little driving, about 40,000 since 1992). It ran fabulously...for 104 miles when it shut down and never restarted again. Now, after a $2400 tow back to my home (600 miles from Yellowstone Park), I replaced one of the coils before I started through the diagnostics. Fuel pumps to the rail. Spark at both coil wires and at a spark plug from each bank. I presume the ignition control modules are ok because I'm getting spark. Took the distributor apart per instructions, all good. Inertial switch was down, raised it and reset it down. Can't find an air sensor flap to play with.
I'm totally at a loss. Any one have any ideas?

Or would it b easier to put a 350 engine and manual transmission in?