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New Guy with a problem [ENGINE MANAGEMENT FAULT]

1706 Views 2 Replies 2 Participants Last post by  simon.coleman
Hi All,

I have a 2003 XJ8 (350) and I would like to try to solve a engine management fault by replacing the Fuel Purge Valve Part No C2C21972. The reason for this is that I have intermitent loss of fuel pressure and I think a possible cause may be that this valve is staying open and returning fuel back to the tank when it should be closed. This could be totally wrong but everything else has been tried. I cant find a detail of where this part is fixed on the car. For some reason I think it's in one of the wheel arches somewhere. Has anyone ever changed this part and can give be some guidance. I have a permanant orange warning light ( which will go out when reset but come back on after a few minutes of driving (not when idling) and an intermittent restricted performance message combined with a loss of power.
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My X350 technical notes for the fueling system has nothing called a Fuel Purge Valve, but does have a Parallel Pressure Relief Valve, shown on a diagram as situated in the fuel tank.

"The function of the valve is to : -
- assist engine start by retaining a pre-set fuel pressure in the fuel delivery line and fuel rail
- limit fuel rail pressure due to temporary vapor increase in hot conditions
- limit fuel rail pressure caused by sudden load changes, such as fully open to fully closed throttle transitions
- prevent leakage from the tank in even the fuel delivery line is severed"

Question - is this your problem component ?

Where did you get that part number from, as a search on it gives your description ?

There is, of course, a purge valve in the evaporative emissions control system which recovers fuel vapour, (petrol) into a canister called the EVAP canister, from whence it is purged into the engine via the Canister Purge Valve. This vents the vapours into the inlet manifold. The valve is controlled by the ECM and operation is based on engine operating conditions using: -

- engine speed and load
- coolant temp
- time from engine start-up
- closed loop fuelling.

The EVAP system has no influence on fuel rail pressure, other than the ECM controlling it, bearing in mind that the EVAP purge cycle will be putting fuel into the system as well as that passing via the injectors, but this should be controlled by the ECM.
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