www.jec.org.uk

Hello folks,
I may have a fuel pump fault on my XK8. Please Let me know what you think to the following. It's a 2005 XK8 with 107000 on the clock. During heavy acceleration it holds back (intermittently). Viewing the live data on a diagnostic device, the fuel pressure reaches 70 psi during overrun, and around 55 normally. During the fault condition, it drops to 10 or 12 every time.
No error messages or trouble codes displayed or lights on the dash.
I'm hoping a partially clogged fuel filter is the cause so I'll try that first,
Next up, I'm hoping it's a loose fitting on the top part of the pump (Reverend Sam's YouTube video)
last resort, I'll throw in a new pump. Even with this I'm hoping for a short cut by accessing through the sub-woofer orifice. (Does this work on the 4.2?)

Any light you can throw before I break out the spanners and the wallet appreciated.

ps, I'm still delighted with my XK8, I even added my wife to the policy. After just 20 yards - I saw the famous XK smile on her face too.

regards

Chris Holloway

I`ve had a similar issue on my old V8 4.0 S-type. A change of fuel filter cured the issue. What came out of the old filter was interesting to say the least.....black/brown with a very high water content. New Marle fuel filter fitted and a couple of bottles of Dry Fuel from Halfords added. No further problems after that. I`d suggest after the Dry Fuel addition has been run through a tank of fuel, that a couple of bottles of Liqui Moly injector cleaner and also a couple of Oxy Cat catalytic converter cleaning fluid lso be added to future tanks of fuel. Those three products together with Wynns Engine Flush will help your engine no end.

The V8 Jaguar family all share the same core engine range. Only timing gear and injector designs differ between the 4 litre and the 4.2. Most of the other gear is very similar across the model range as are the occasional running issues.

Mike K

The fuel pump for the 4.2 litre engine has its output pressure controlled by a separate module that provides a pulse modulated voltage to the pump to control its speed.

While the fuel filter is a good (easy!)starting point, before diving into pump replacement (difficult!) it would make sense to check the wiring and connections to the module and, if possible, the modulated voltage output to the pump from the module as the fault occurs.

Fuel pump modules on ebay seem cheaper than fuel pumps!!

thanks gents,
I'll try all of these and come back to you with the results.

Chris

Sorry for the delay on the update (Weather and work interrupt).
It's looking like good news, a change of the fuel filter gave instant results. The fluid from the filter once disconnected was black rather than petrol coloured. The body of the filter was corroded and had probably been on for over 5 years and perhaps 60k miles. I have been/continue to add the various fuel additives and plan to use the Wynns engine flush before the next oil change within the next month.
Thanks again for your help,

Chris