136000 on the clock now, daily driver for the last two years. Last couple of days it has had a very hard time starting when cold. After a few tries, it will catch and when it does everything is fine. If the engine is warm, it will start right up. This happens when the engine is cold (our temperature here in the Austin area did not drop below the 60s) yet so it is definitely not weather related.

At one occasion, I did turn the key on and off 3 times to see if priming the fuel pump would help and it did. It started right up. The MIL did not turn on.

I am suspecting a marginal fuel pump. I will hook up my IDS / SDD setup to see if there is any record of malfeasance.

Any one else with a similar experience?

 

There's quite a trail of failed fuel pumps but that doesn't say yours is on its way out (though it may be).

 

I just realized that I have been driving without the gas cap on since last fill-up. I had lost it. I ordered one from Amazon. May be it is a contributing factor?

 

I'm amazed it didn't flag any codes.

 

Not only that I'm amazed the fuel gauge is working without the cap. When I didn't screw mine in properly after filling up one time the gauge sat on zero. Screwed it in and up to full.

Getting back to the starting problem. Could also be that the fuel rail is not holding pressure. You can check the fuel pressure via OBD if you have Torque or another app, not necessary to have SDD.

I believe there is a check valve somewhere between the fuel rail and the fuel filter under the front seat (under the car). I took off the filter once and was very surprised to find the rail under full pressure.

 

I just got my replacement gas cap from Amazon and it is an original Jaguar part. Pretty cool. Part #: XR819276.

I did get the fuel cap warning once in the last 400 miles or so I have driven the car w/o a fuel cap.

 

I hooked up my IDS/SDD setup but there were no relevant codes registered. I then registered my AutoEnginuity setup and also hooked up a fuel pressure gauge on the fuel rail (passenger side, rear of the engine) and realized that pressure does not hold at all. When the switch is turned on, on the first time it only goes to about 20 psi and then back to zero and on the second time it goes at about 60 - 70 psi and then immediately goes back to 0. I verified this also with AutoEnginuity....

The supercharged engines have two fuel pumps and I am assuming both have check valves built in? Is there a troubleshooting procedure that will allow me to isolate which of the two pumps is defective?

 

Video link of my fuel pressure readings. I turned the ignition on and off twice and on the third attempt I started the engine. As you can see, the pressure is not being held when the engine is off

 

Some pictures of the new fuel pumps I put in my XJR here https://www.jaguarforums.com/forum/s...-pumps-130587/

It's not obvious to me where the a check valve is located, but it looks like there is a white plastic something on the left hand pump, which could be a check valve. EDIT no after checking all the pictures I see two of them.

There are three lines that run across from the right hand pump to the left hand pump. The left hand pump is where the line to the front of the car gets connected.

Three lines are;

Feed from the right pump to the left pump, the main delivery line.
Transfer from right side of tank to left
Transfer from left side of tank to right

Hope that helps you somehow.

 

Some more info here.



So I guess the two white plastic check valves in the pictures are the ones referred to in the Tech Guide.

 

Lagonia,

Another possible suspect might be the Fuel Rail Pressure Sensor or "transducer," which is mounted at the rear end of the left fuel rail (as viewed from the driver's seat). It has both an electrical connector and vacuum line port. I haven't studied its operation on the X350, but presumably it works in conjunction with the check valve(s) to maintain pressure in the rails even when the engine is shut off. It seems unlikely that its default condition would be to open when electrical power is shut off, but it might be worth at least inspecting the electrical connector and vacuum hose for any obvious problems.

On the earlier cars with mechanical/vacuum operated FPRs, FPR failure is a well-known cause of hard starting. I assume the same may be true on the more modern cars.

Hope it's something easy to diagnose.

Cheers,

Don

 

Awesome! Thanx Cambo, that does help. Need to source fuel pumps now. Gaudin wants over 1K $ for each one of them! I am hoping that there are reasonably priced aftermarket pumps out there....

 

I never found any complete aftermarket pumps, I paid about GBP1000 for the pair from a UK supplier last year. If the pumps are able to deliver 70psi then the motors are still ok, or close enough to it, it's likely just the valves which are a problem.

 

Don,

I believe the "transducer" you are talking about sits further back from the fuel filter. There are no electrical connections to this device. There is two lines going into it, one soft and one hard. See attached image.



I have no idea what this thing does.

 

The fuel pressure sensor is mounted on the fuel rail, left hand side up near the throttle body. It's a differential sensor referencing to the manifold boost pressure after the supercharger.

That thing in the line that has nothing connected to it... I remember doing a search for the part number that is stamped on it when I was having my "fuel troubles" I don't remember exactly what it is now, but it was not anything important enough for me to chase it up.

What's the part number on it?

 

Part number is 2W93-9S446-AC. It appears to be a EMISSIONS FUEL VAPOR PURGE SOLENOID VALVE from my limited search. Probably irrelevant to my fuel delivery problem.

 

Yeah that sounds like it.

 

Just re-read your opening post, 136'000 miles, the pumps are due for replacement anyhow...

 

 

Sorry mate but nothing lasts forever...especially things with moving parts.

The pumps on mine were on the way out at 108'000, I know of another XJR that had them replaced at 150'000.

Your mileage is up there, that's all I meant.