Trying to see if anyone has run across something similar. 94 6.0 XJ12 won't rev past 4000ish RPM. I can hold it wide open and it stays flutterings around that 4k mark. Under load it starts breaking up around 3500. I recently obtained the car, it was destined for the crusher and had already been prepped so don't jump on me for doing this to it. Ran it at Laguna Seca last weekend. Mechanically stock but the interior has been stripped with the original wiring left in place. It throws a code for Fuse1, Fuse2 and PAD which apparently it has done for some time. Obtained the car with a BMW fuel pump plumbed inline to replace the stock pumps which weren't working properly. I replaced both in tank pumps with new Walbro replacements and removed the BMW pump. I am measuring around 30lbs of pressure right after the filter and it drops to 28lbs at full throttle/no load. Seems like that should be sufficient pressure.

The car ran the first 45 mins of the race with this misfire/no rev issue. Basically tried to egg under the throttle pedal to get it to upshift as soon as possible. I was messing around with the shifter and moved it from the left gate to the D position on the right and the car took off and ran great. Had to relearn how to drive it. Drove it for another hour running great. Brought the car in for fuel and driver change. As part of that, we kill all electrical power from the battery to the car. From then on through the rest of the day the car resumed it's won't rev condition. I've ordered up service manuals but until they arrive, anyone have any ideas?

 

https://www.jaguarforums.com/forum/x...ne-side-62789/
this link above might help i have the same car and i had a problem with one of the coils going out and it had no power cause only the left side of the engine was firing

 

Ok, thanks. I can't seem to find a testing procedure for testing for a faulty coil so I guess I will wait until the manuals arrive and see what they say.

 

The XJS manual published by Jaguar Cars, LTD arrived today. I couldn't find a XJ12 manual for the 6.0. The manual gives instructions for removing the coil which I'm fairly certain I could have pulled off without directions. There is no procedure for testing the coils listed in the manual. Overall, it looks pretty weak on diagnostic tests. Does anyone know the procedure for coil testing on the 6.0?

 

i checked mine by eye, its not the right way i wouldn't think but it work for me, i just pulled a from a spark plug wire and put on a spare spark plug to see how the spark was coming from that wire while the motor was running and sure enough the right side of the motor had little or no spark and the left side of the motor you could see it had a good spark

and remember you must touch the threads of the spark pulg the metal to ground it to get a spark and turn off the motor between checking wires or it will shock the s*** out of you
good luck hope this helps
and one more thing if its not getting spark some where it could be any where in between the coil and wires cause your not testing just the coil its self

 

Soo, I think the problem is solved. Not ignition related. Short version - 1 of the fuel pump grommets and both 1-way valves in the fuel pump canisters were bad. The grommet is located in the top of the cannister where the fuel pump outlet goes into the cannister lid. I re-attached the grommet and replaced the 2 1-way valves with aftermarket ones from a diesel. I think the two fuel pumps were working against each other instead of trying to deliver all their pressure to the engine. 40 bucks later at least the car will now rev with no load. Will need to arrange a track day to see how it drives. Thanks for the suggestions.

 

Good that you seem to have found a solution.

But PLEASE PLEASE post up a shed load of pictures of the car on the track, in the pits, in the garage or just on the trailer.

We don't see enough comp cars.

TIA.

 

It's next competition event will be a true 24 hour race at Buttonwillow 6/30-7/1 with the 24 Hours of Lemons.

 

Cheseroo -

I am sorry to hear about the revving issue, but am glad that you figured it out. Once again, our team is glad that this car found a good home, but it is unfortunate that it had problems at it's first race. Hopefully it runs much stronger at Buttonwillow. I (Eric) am planning on being there as an arrive and drive, so if you need another, let me know. Ed may also be willing to Pit Crew for you if you need another set of hands and eyes. If you ever have any questions about what we did to the car and any nuances that you come across, shoot us a question and we will try to answer it. Oh ya, and the ECM codes have always been there. They are just saying that you are missing some fuses from blocks 1 and 2, and that the ABS sensors aren't working.

And now for some pics that were requested (from before the change in ownership). I am sure that Cheseroo will have more to post as well...

 

That explains why I thought I was seeing things.

Thanks for posting guys, best of luck for the future.