Hi everyone,

I’m having a frustrating issue with my Jaguar and hoping someone here might have come across it before.

The car has ran out of fuel when the gauge shows around 1/4 tank remaining twice now. When I refill it after "running out," it only takes about 60 liters, which is roughly 3/4 of the tank's capacity. This suggests that the right-hand side of the tank is empty while the left-hand side is still half full, suggesting the level sensors are working correctly.

To try and resolve the issue, I've already:

• Replaced the fuel pump and level sensors (about a year ago).
• Run a tank of diesel with biocide and Liqui Moly Pro-Line Diesel Cleaner, just in case it was sludge or contamination causing the problem.

Unfortunately, the issue persists. It seems like the fuel isn’t transferring properly from the left side to the right side of the tank, but I’m not certain. I assume it's something to do with the suction pipe from left to right, maybe it has a split in it, or is partially blocked? Is it possible to remove this pipe to check it?

Has anyone else experienced something like this? Any suggestions would be greatly appreciated!

Thanks in advance! 😊

 

If i remember correct threre are an pump inside of tank for noving fuel from right side of the tank to left side. The pump is located on same assembly than actual low pressure fuel pump / fuel sender.
If that pump do not work your left side of tank do not feed to right side and about 16-20 liters will remain. Note: High pressure diesel pump do not like at all if running dry, so don´t drive with low tank until fixed.

Edit: From service and repair manual:
"Fuel pump module operation description:
The low pressure fuel lift pump is located in the fuel pump module. The lift pump is employed to provide a low pressure supply
at approximately 0.5 bar, to the common-rail high pressure fuel system and maintain an equal fuel level in both compartments
of the saddle tank.
The lift pump operation is controlled by the Engine Control Module (ECM), via the fuel pump relay located in the Rear Junction
Box (RJB). When the ignition is switched on, the fuel pump operates for 25 seconds to build up fuel pressure. As engine
cranking commences the fuel pump stops running until the engine starts. This function is employed to decrease load on the
battery.
A three way connection is located on the top of the module. Two outlets supply the jet pumps, the other outlet is the pressure
feed through the pressure regulating valve to the fuel delivery line. The module incorporates a jet pump which draws fuel from
the Left Hand (LH) side of the tank to the Right Hand (RH) side to be collected by the fuel pump module."

Is your fuel piping original or modified? Is the fuel filter correctly connected? If i understand this correctly: Jet pump work with fuel return flow?

 

Well that would make sense I suppose. I’m assuming if I buy a new low pressure unit, that will also include that jet pump?

 

Check my edited post above

 

Ohh... Yes.
I read the manual forward:
"JET PUMP
The fuel system incorporates twin jet pumps which are integral with the fuel pump module. One jet pump collects fuel from the
RH side of the tank, and the other draws additional fuel from the LH side of the tank through a suction line that is mounted on
the carrier. The jet pump operates on a venturi effect created by the fuel at pump output pressure passing through the jet
pump.
The prime function of the jet pump is to collect fuel from the LH side of the tank and transfer it into the fuel pump module
swirl pot on the RH side of the tank. The jet pump feature ensures that fuel is drained from the LH side of the tank before fuel
run-out on the RH side of the tank."

You just might have lose pipe etc..

 

I’ll take a look tomorrow to see if there’s any loose connections. My worry is, if it’s a split pipe or a blockage, I’m not sure it’s possible to actually remove and replace the pipe to the LH side of the tank. Which would mean a new tank I guess

 

Its very interesting construction. Sneaky way to make transfer pump by jetting.
I suspect that the piping inside of the tank is only snap-on mounted. Maybe pipe have got loose on left side? You can try compressed air against flow direction for blockages.
Btw: x351 service and repair manual have very good pictures. I sent you PM for it.

 

So after a lot of trial and error I may have found what the issue is I hope. Since the initial problem I’ve had a number of other weird issues, such as the service light suddenly saying 900 miles until a service (1 month after it was reset) and then 10 miles later saying service due now. Random intermittent restricted performance mode. Intermittent rough running and idling. Everything leads to an issue with the fuel system.

When the high pressure pump died a few months ago, the garage replaced it but the car didn’t start still. They ended up having to replace the injectors as meta shavings had made their way into them and blocked them. At the same time we replaced the fuel filter (which has been replaced again since when it was serviced), and flushed some of the lines.

I fear that some shavings have made their way down the return lines and either blocked the lines, blocked the pump, or blocked the jets. Either way something isn’t right.

Now I could well be wrong, but I’m just trying to work out what on earth is causing all of these issues, and this is the only theory I can come up with.

It’s booked into Northfield Jag specialists in a couple of weeks, so hopefully with a proper flush, and most likely a new low pressure pump, hopefully that will solve my issues. At least I hope, otherwise I think it’s time for this old jag to finally go.