Can anyone point me in the direction of the full explanation of the Ford returnless fuel system, I know I got a copy which was linked from here before but can't find it now and remember throwing out the printed version I had. It was a really comprehensive explanation of how the system works, probably running to about a dozen pages.

All I can find linked on here is this one - Under Pressure: Maintaining Ford?s Electronic Returnless Fuel System - but would now really like to read the other again to try and figure why my car is not running as smoothly as it should with fluctuating fuel pressure according to my OBD and the Torque app.

 

If no one knows where it is maybe I dreamt it!

 

This is a very simple explanation of the difference:
Returnless Fuel System comparison Car Gas Flow Diagram

 

Jaguar describe the system as follows in their Introduction to Servicing the XK8/R 2003

Fuel Pump
To support the installation of the 4.2-liter engines and continuing the drive for fuel consumption benefits, a new fuel system including fuel tank, fuel pump, pipes, breather pipes has been installed.

The XK now benefits from the use of the return-less fuel delivery system very similar to the X-Type and S-TYPE models.
One major change on supercharged (S/C) variants is the use of only one fuel pump instead of the usual two as used on all previous S/C models (XJR, XKR and S-TYPE R).

The fuel pump uses the same principle of operation as the on the X-TYPE where the ECM monitors differential pressure across the fuel injectors and the injector pulse width and duration to accurately calculate the fuel quantity being delivered to the cylinders. It uses this to demand a specific fuel flow rate, which it communicates to a fuel pump driver module located in the right hand side rear wheel arch.

The ECM use a frequency of 150 Hz (PWM) signal during average conditions, varying its
duty cycle between 4 and 50% to control fuel delivery rate or turning it to 75% to turn off the pump.

 

Thanks for that, not sure it helps me pinpoint why I am getting rapid fluctuations in fuel pressure but between the two explanations it seems like it may well be the pump, unless there is a sensor problem or the pump driver module isn't working correctly. Unfortunately that leaves a few things to check!

This is screengrab to show how the pressure is fluctuating - I think the graph shows 10 seconds history and this was driving at a steady pace with a constant throttle position:

 

I had a surging problem, which I suspected could possibly be a fuel pressure issue and therefore I have watched and logged my real time fuel pressure extensively while driving. As it turns out, my issue was the throttle body, and had nothing to do with fuel pressure. I can confidently say that your pressures aren't fluctuating any more than normal, and honestly, there is very little variance shown in your graph. The system does minutely continuously adjust pressure based on many variables - just because you are on a flat road with constant throttle doesn't mean the ECU isn't continuously adjusting many engine management parameters. Whatever you are chasing, I suggest, has nothing to do with fuel pressure.

 

Thanks Steve - what was the issue with your throttle body? I've cleaned mine but it made very little difference. It sort of feels like there is an air-leak in the system somewhere but the vacuum readings I am seeing are constant - much more so than the fuel pressure!

Of course, I didn't check the pressure when it was running smoothly so I have nothing to compare the current readings with, just that some of the hesitation seems to correspond with the changing pressure. It only surges on a light throttle, acceleration is OK and it is much smoother at higher revs - anything over 3k and it barely surges at all.

 

I would agree with Steve, the +/- 1psi in your plot is normal for the system.

Is there a speed dependence? The early 6spd had trouble with a seal in the lockup torque converter and it can cause a sort of surging, often accompanied by a sort of rumble strip noise. Usually is worse when the engine/transmission is cold.

 

https://www.jaguarforums.com/forum/x...1229-a-119734/

https://www.jaguarforums.com/forum/x...ighway-118098/

Andy, above are the 2 relevant threads (sorry I didn't keep 1 thread for all, I should have). They should provide you with a good explanation of the problems I experienced. Please ask me additional questions if you don't read about some of your symptoms.

 

Thanks Charlie and Steve.

I read the post from Charlie and can certainly relate to that - on a light throttle I am getting a vibration through the car from about 60 to 75-80mph (a real pain with a 70mph limit in the UK) which goes if I move the gear lever to 5. Sometimes on gentle acceleration at around 50mph it almost feels like their is a wheel badly out of balance, but it doesn't always do that. Both are worse when the engine is warm actually, although when I am driving away from the office soon after leaving, so with a cold engine I do go up quite a steep hill with a 30mph limit and can get some surging but it is a lot less than it was before I had a gearbox oil change and software flash.

Then I read the other threads from Steve and what I am getting sounds just the same.

So maybe I need a new torque converter, gearbox and throttle body. Or maybe it is time to change the car!

At least you have reassured me that the fuel pump may not be the issue, although I sort of hoped that would be it as it is relatively new and therefore still under warranty!

 

There is a TSB for bad torque converters on 2003 MY...you can find it here on the forum.

 

Thanks Steve,

I used the OBD and app today to watch the revs whilst driving at a steady pace and essentially get a graph similar to the one I posted for the fuel pressure so guess the diagnosis of torque converter is pretty much likely to be the case.

With 135k miles on the clock I'm thinking the cheapest solution will probably be a replacement box from a breaker, only one I can see on eBay is from a 2007 car so need to check if it is compatible - I'll start another thread for that though.

 

Gentlemen:
On an 04 XKR car ran fine to the store came out 10 min. later it won't start,starter worked car fired but wouldn't run. took the fuel pump out tested it passed. re-installed and now it doesn't run. ?Query? On the white plug that supplies power to the pump what wire(color) carries current? If there is no power where do I turn to next? I'm getting deperate, thinking of running a switched power line to the pump and bypass the module.
thanks

 

You won't be able to directly connect the power to the pump because this system varies the pump speed to control fuel pressure.

I'm also not sure that the pump is ever meant to see 12V directly, the driver module varies the duty cycle between 0 and 50%, so it would only get a voltage about about 6 or 7 at max. Hope you didn't toast it.

How did you come to suspect the fuel pump? Was the fuel pressure low? Any codes or other symptoms?

Confirming a bad driver module will likely be difficult without having the dealer level scan tool, it helps to know what the ECU is telling it to do so you can determine whether it's an input problem or an output problem.

As a starting point, can you confirm that the driver module has a good power and ground?

 

Thanks for the reply, here's what I've done. I checked the Schrader valve, no gas in the fuel rail. Took pump out through subwoofer(cut some metal), connected 12v. momentarily it worked. No codes. I thought it might be the inertia switch (will check in a bit) will also check driver module for power and ground. I wanted to check power in the white plug but couldn't find a wiring diagram(if you know where to find it let me know)
Thanks for your help

 

FT3 is a 6 way natural color connector, which probably means white. Located on the fuel tank evaporative flange. Is that the one you are looking for?

 

thanks for the diagram, here's what I found. 11.50 v at the red and/blk in the white plug that supplies power to the pump. Noticed that the plastic piece that snaps into the pump(this line supplies gas to the engine) works it way out of the snap connector. Will try to wire it together like Sam1174 did on YOUTUBE. So there's power going to the pump, will try to fix this issue and keep you apprised.
Thanks Again