I see them for sale on lots of websites, so I know they exist. The JTIS mentions it but it doesn't show a removal and replacement procedure. I'm thinking that there's a slim chance that it may be causing my hard starting issue. If it is anywhere except the fuel tank I'm going to replace it. If it's in the fuel tank I'm going to replace it at the same time I replace my fuel pump. I just need to know where it is.

 

Sam, it is item #4 on the fuel rail on a 2003.

 

Thanks! Fortunately I have some cool watchmaker tools, including several loupes. I was able to pull out my loupe set, and using the one with the second highest magnification I was able to find #4 on the diagram! It looks pretty easy to change, so I think I'll swing by my local Jag dealer tomorrow to grab one. This is a shot in the dark, but hopefully it will prevent me from having to pull the fuel tank.

Oh yeah... for those of you without jeweler's loupes, it is located at the rear end of the left fuel rail. The fuel rails are right on top of the engine. If you take off the plastic cover they are the hard metal tubes on either side of the engine

 

I really did try to enlarge the image in EPC before I copied it, but it just got clipped in the small viewing window......really I did.

BTW, was your loupe from Harbor Freight?

 

I ran across this and thought it would help. It says it is for 1997 on...

 

Replace the vacuum hose as well. It's possible that a new FPR could solve your hard start problem....

Shop around, they are kinda expensive. I think I paid $140.

 

Well did you find the problem?

 

Actually that thing in the diagram is just a fuel pressure sensor. It tells the ECU what the pressure is, but it doesn't actually regulate the pressure. I know the sensor is good because I can hook my spiffy OBDII thingamajig up to the car and read the fuel pressure. I can see that the pressure is normal once the engine starts, it's zero before the engine starts, and it gradually declines after I turn the engine off. So the sensor is good.

Here are my thoughts, but maybe I'm completely wrong. Even if the check valve in the fuel pump was bad (assuming it even exists), the fuel couldn't flow backward into the tank as long unless there was a vent of some type that relieved the suction of the backward-flowing fuel. Just like with a straw, you can hold water in a straw if you put your thumb over the top end. Something in the Jag is allowing the fuel to drain back into the tank. Whether it's a valve in the tank or a something venting air into the line at the front end, something isn't right.

A complete fuel system diagram would be helpful, but I can't find one in the JTIS.

 

I was unable to find anything on Alldata but I will continue to look. Have you thought about the fuel recovery system & emission systems and a vacuum leak? Use this link to get you to a parts breakdown on the entire system and I think you can put it together and figure it out I looked at 1G. It is better than nothing.

http://www.captainjaguarscathouse.co...F_3/1_G_07.tif

 

Could that part be a sensor AND a regulator combined? I saw contradictory information...EPC listed it as a transducer, a dealer online catalog listed it as a pressure regulator. If it was just a pressure sensor (transducer) why would it have a vacuum connection?

 

It's all the way over at the far end of the fuel rail. For it to be a regulator it would have to be at a point between the fuel pump and the fuel rail. It's measuring the pressure at the farthest point from the pump, therefore I don't see how it could act as a regulator.

 

On my 2000 XK8 (not R) the FPR is on the right side (passenger side) fuel rail at the end nearest the windshield. It's right on top, easy to see and reach, held in place with a retaining ring/tang setup and a small bolt. The end you see is about the size and shape of a large bottlecap and has a 3/8" vacuum hose coming right out of the center of it. (The other end of that 10" hose goes into the throttle body - replace the hose).

Perhaps it is relocated on a MY2003, you should have found it right off...

 

Thanks, Gus, but it looks like that diagram is for a pre-2003 XK8. In 2003 Jaguar changed the fuel system and got rid of the return line to the fuel tank. After 2002 they used a different system that electronically controlled the fuel pressure. That's why the check-valve ended up not working for my car. When I would shut off the engine the heat from the engine would cause the fuel in the line to expand. The check valve prevented it from going back into the fuel tank. Then that pressure prevented the injectors from opening. If I would relieve the pressure by pushing on the shrader valve I could then start the car. Or if I waited a couple of hours for everything to cool down I could start the car. But after I turned off the engine I had about 5 minutes to restart it, otherwise the pressure would build up and I either had to wait or vent in order to start the car. People with the return line wouldn't have to worry about that because excess pressure would just be vented right back to the tank.

Anyway, I'm back to square one. When this problem originally started it would happen intermittently. Now it happens just about every time I start the car. If I start it within 15 minutes or so of the last time I turned off the engine, it will start up instantly. But any longer than that and it takes 5 to 10 seconds of cranking before it finally starts. It always starts, but the cranking can be a little embarrassing.

 

OK, I see now...there is no conventional fuel pressure reguator post-2003. This is the Ford returnless system that controls fuel pressure by Pulse Width Modulating the fuel pump (the controller for this looks like it is in the RH trunk floor area) based on sensor feedback. The sensor is referenced to Manifoild Absolute Pressure...so that is why it has the vacuum hose.

Here is a writeup on the system:
Under Pressure: Maintaining Ford’s Electronic Returnless Fuel System

 

Great write up on the system!

 

Sorry Sam I was not sure if it was the same but thought I would give it a try. I am still looking but I feel the vacuum system may be part of the problem. I will keep an open mind and I hope others chime in.

 

I'm not burdened by much knowledge here, just thinking out loud ...

At least some of these returnless systems have a mechanical regulator in the fuel tank, as well electrical control of pressure (PWM of pump voltage). Don't know if that's so for the XK.

Seems like there must be some way designed in for fuel to flow back to the tank on shutdown, otherwise as it sits there heating up in the fuel rail there would be tremendous pressure buildup going along with that.

Have you measured fuel pressure at these times?
- cold start
- during that interval after shutdown, when you know car will start easily
- during the interval when you know it will be hard to start
(If I missed this above, sorry)

On the other hand, if pressure is not held high enough, fuel in the rail could be vaporizing as it sits there getting hot, which would certainly make for hard starting. (some systems detect high fuel temp and raise pressure to prevent vaporization as needed, but when everything is shut down??)

 

Yep, I've measured the fuel pressure at various times. Before a cold start it is zero. with the engine running it's around 40 PSI. After turning off the engine it quickly declines back to zero. When I had the check-valve installed it would climb after I turned off the engine, peaking around 60 PSI. That's when it wouldn't start at all. I learned that by venting a tiny bit of fuel from the Shrader valve on the fuel rail I could then start the car. I don't know this for a fact, but I assume that the high pressure prevented the fuel injectors from opening. Relieving the pressure allowed them to open and the car would start instantly. Also, waiting a couple of hours would relieve the pressure and the car would start instantly. The check-valve was keeping the fuel up at the fuel rail, it just wasn't allowing the fuel injectors to open when the car sat for a few minutes after turning off a hot engine.

 

I was thinking of the pressures measured after turning the key to on but before engaging the starter. Should they / do they sort of match up in all cases?

Can high pressure keep an injector from opening? (I don't see how, just don't know)

 

Right now, with a cold engine, the pressure is zero. I know this because when I press on the Shrader valve nothing comes out. When I turn on the key the pressure goes up to 3-5 PSI as measured by my OBDII tool which is getting the pressure from the sensor on the rail. When I crank the engine the OBDII tool cuts out because it's not getting power, but the engine cranks for 5 to 10 seconds. Towards the end it starts to fire. It acts like it's about to start. Then it finally fires up, runs rough for about a second, then it runs fine.

But check this out: Each time you turn on the key the ECU runs the fuel pump for a couple of seconds to pressurize the fuel line. If I turn the key to "Run" (not "Start"), then turn it off, wait a few seconds, turn it back to "Run" again, turn it back off, and repeat this about 6 or 7 times, the car will start instantly. By turning the key on and off over and over I'm running the pump enough to pressurize the fuel lines. I've confirmed this with the OBDII tool. After several on-off cycles with the key I'll have from 20-35 PSI in the fuel line and the car will start instantly.