While diagnosing an acceleration stutter with my '99 XK8, I've found that my fuel pressure is running low (35-30lbs ignition/on/acceleration) and that it doesn't maintain pressure (albeit the pressure drops very slowly).

I'm trying to track down the trouble part, but I was hoping to get confirmation on the list of all possible fuel system components (that run between the tank and rail).

• Components replaced:
  • Fuel pump x2 (just to completely rule out a faulty pump)
  • Fuel strainer
  • In-line fuel filter
• Components remaining?
  • Fuel Pressure regulator (on the end of the fuel rail)
  • Fuel tank/pump valve? Link
  • Fuel pressure sensor? Link

Am I missing anything else that could be causing low fuel pressure?

 

I would have started with the fuel pressure regulator as it is relatively cheap and the easiest thing to replace. I think you have everything other than a stuck open injector or two but there would be other symptoms for that.

Richard

 

That's interesting - the 4.0 XK8 only has one fuel pump. The pressure sensor you refer to is the fuel tank pressure sensor, rather than fuel pressure - that isn't going to be in the fuel line surely? The 4.0 cars don't have a fuel pressure sensor, so I think you can rule that out?

 

Read you OBDII codes and then post the codes.

 

I started with the pump because a couple years back it died on me and I replaced it with a cheap pump at the time. Between the original post and now, I replaced the pressure regulator and it unfortunately didn't resolve my problem. I'll keep the stuck injectors in mind, though.

I thought the same, but then I stumbled on that store list that I linked above, so it made me question. Thanks for clarifying.

I actually can't get any codes to show (pending or confirmed). I tried using OBDII for pressure monitoring, but unfortunately my scanner doesn't support it.


This weekend I plan to to dissemble the tank again and check all the pump's wiring continuity (low voltage delivery?), along with attempting to replace the rubber hosing within the tank (vacuum leak?).

 

How are you testing fuel pressure? With a gauge attached to the Schrader valve on the fuel rail?

 

Yeah, but soon I'm going to attempt to test the pressure inline at the fuel filter.