Evening gents,

Been having an odd issue with my 02 XJR-100 since I purchased it at the beginning of the summer. Over 4000rpm, the car experiences power loss and a WHUMWHUMWHUM pulsation through the drive-train. I've had others suggest it could be a differential issue, but my mechanic can't explain it and obviously has difficulty diagnosing an issue over 4000rpm via road test. From my experience, it feels like a fuel scarcity issue. I replaced one of the fuel pumps (and filter) earlier this summer, but elected not to change the second one at the time. Has anyone experienced a similar problem? Let me know your thoughts and I'll attempt to answer any questions to the best of my ability.

Cheers,

David

 

This, almost assuredly, sounds like the secondary fuel pump not engaging when the S/C is calling for it. You can remove the fuse relay for the 2nd pump and drive it to see if the condition is the same. That should tell you your answer....but, to ask first, do you have any codes?

 

What I just did to diagnose fuel pump issues was to install a fuel pressure gauge with a long enough hose to mount it where it was visible from the drivers seat (outside, held down by the wiper!) Then I took it for a drive.

I strongly suspect your secondary pump, though. Unfortunately, it is unlikely to throw any codes. Mine never did.

 

Hi gents,

Thanks so much for the quick response. You guys are awesome. The car isn't throwing any codes - I was suspecting that it was the secondary fuel pump as well. If there's any further information I can provide before ripping back into it, please let me know.

David

 

Okay, so I just yanked that 2nd fuel pump relay and took it for a drive. As soon as it started up, the Restricted Perf. light came on. When I mashed the throttle, it wouldn't even let me get to 3000rpm before the fuel cut out and it started bucking like an angry bronco. So basically it magnified the problem by about 5x at 1000 lower rpm. Thoughts?

 

You sure it's not the s/c belt slipping above 4000 RPM.

 

I believe there is a self test of the pumps on start, pulling the relay will trigger the error. I presume you were driving under load as there is a rev limiter in neutral that kicks in at around 3k.

 

Might it be a blocked cat conv? Tend to show up as power gets highish.

 

.....a +1 JagV8's suggestion. Also, when was the last time you changed your fuel filter?

 

Correct. I was driving under load.

 

Changed the filter at the same time as the pump, so about 2 months ago. No real way to check if it's a blocked cat without replacing the cat either eh? Darn.

 

Would it squeal at all? I can't be 100% sure of anything at this point.

 

Not trying to help you spend your money, but have you tried one of these... https://www.amazon.com/BAFX-Products...QFZ415CWDT7VYR
...you have real time sensor evaluation, you can do screen shots, retrieve and delete codes and send reports to your email to print out for evaluation or to take to your mechanic. Yes, the one I listed is for US models, but there are plenty other ones out there for elsewhere. There is another one other members are recommending, but I don't recall it at this time.

 

Not really true.

You can try an IR gun to see temp drop across each cat.

Or MAF value at WOT to see if it's as big as it should be.

Or remove cat(s) and look inside - actually you can often remove O2 sensors and use a borescope.

Sometimes you can just listen near the cat as the car is revved.

 

Thanks for the feedback guys. It's really appreciated. I feel like this is going to require some more in-depth diagnosis. Not sure if there may be any correlation but I'm also having an issue with filling up the fuel tank (will not go above half) and since I've owned the car, there has consistently been a low whine throughout the cabin of the car that sounds like speaker feedback (or like a fuel pump wine). Like I said, not sure if there might be any correlation but I felt obliged to include that information as well. I'll continue to chase down the source of the issue and report back

 

Ahhhh, I forgot your the one with the fuel tank filling issue...https://www.jaguarforums.com/forum/x...-issue-167624/
I came to the immediate aspect that the noise you described may be the pump. But aftermarket ones do make noise depending on the brand. That doesn't mean it couldn't be ready to give up the ghost.

 

Okay so I can officially say that the supercharger belt is not the issue. Had a look at it last week when I replaced the main drive belt and it seems fine. Up next: Follow Mark SF's idea and attempt to mount a fuel pressure gauge outside the hood area so I can see it while driving and try to identify if there is an issue going on with the pumps. Stay tuned

 

When you get the fuel pressure gauge hooked up, you don't have to drive the car. You could just start the engine, note the FP reading and pull the secondary fuel pump relay and hot wire it on and look to see if the pressure changed. I don't have the specs at this time though.

 

What will that tell you? If the fuel pressure regulator is working, the pressure will be exactly the same with two working pumps running, as it is with one. Also, there is hardly any fuel flow, so this test will tell you nothing about the behaviour under load.

 

I'm working on why not get the Bluetooth OBDII device? You can do a screen shot of the trims and many other readings to post for someone to evaluate. You should have someone ride with you monitoring it and when it starts to do its thing, they screen shot it and on any other readings it gives you. The more info, the better.