I have had a 1994 4.0 L XJS for 21 years (second owner). It has about 55000 miles on it now. On our last venture the engine shut down about 2 hours into the trip. It acted like fuel starvation. It would crank and fire only to quit seconds after starter release. After a 20 mile flatbed tow to our destination, and a couple of hours cool down, it started and ran without a hitch. I hauled it home after the car show on a trailer. It continues to start and run, so no troubleshooting has shown anything. Does anyone have any ideas? Thanks, DH

 

Crank sensor. Been there, done that.

 

Thanks supercharged tr6. Is that the crank speed sensor located on the R/H front of the engine sensing teeth on the crank? Or is there a CPS somewhere else on the 4.0 Liter six? Also is that a supercharged Triumph TR6? I have a much better knowledge of TRs than Jags. Thanks, DH

 

Yes. The 4.0 has only one crank "sensor". I have written on here several times of my experience with buying a non-running Marelli car, as well as my 97 XJR and these "sensors". They give out. The heat and time break down the magnet, and they quit producing as much voltage, which in turn gives the ECU information that is outside the VE tables built into it. The car can sometimes start, maybe even idle, but not run.

The supercharged TR6 turned out to be a non-realized (yet) project that didn't come through. I have owned 15 TR6s through the years, and still have everything for the supercharger project, just haven't followed through. Just sold my 73 that I did a ground up on, putting a 302 Chevrolet, Muncie 4 speed, and Corvette diff with a 4.10:1 gear in. Looking for another TR6 now.

 

Thanks again, I ordered a new sensor a couple of days ago. Hope it will cure the problem. DH

 

I've had trouble with the new sensors and went through a few before finding a random one that is lasting. I guess what I'm saying is, order a spare and keep it in the trunk! Along with an 8mm or 10mm socket (I forget which)

 

Thanks for the advise, I received the new sensor today. Plan to change it tomorrow. When yours failed did your car stop running, or did it just not start with no indications prior to that? Thanks, DH

 

My XJR was running fine. I was pulling away through a traffic signal, and it stumbled. I tried accelerating, and it wouldn't turn over about 3000 rpm. Luckily, I was near my business, limped it there.
My 89 Mareli XJS I bought not running. Turned out to be (mostly) a bad rear crank sensor.
These things go bad. I'm wondering if many Jags were given up on due to these "sensors" failing?

 

And BTW, the XJR did quit running altogether. It did start a couple of times, but until I put that sensor on, it was dead. Weird thing was, it had fire to the plugs. Just sounded out of time when I attempted to start it.

 

Hi !
While you are replacing the CPS you might consider installing the modified
CPS bracket that advances the timing slightly. I did it on my 1994 XJS and
it does make a difference in starting and in the get up and go. Well worth the $100+.
Andy Stodart (XJENGINEER) designed and sells these marvels. You can request
one via an email to Helenstodart@gmail.com.
Regards and P O R - Press On Regardless
Bob Scarborough