Hello, hoping someone can help. I currently have a 2005 S-type R 4.2 S/C, the car starts and runs fine but have restricted performance message on dash, have plugged in code reader and get:



p0628 - Fuel pump A control circuit low
p2636 - Fuel pump B low flow performance
at idle:
FRP 70psi
MAP 6.7psi
MAF 0.02


Now my understanding of the system is that there are 2 fuel pumps located in the saddle tank, one is the main pump and the other is a transfer/jet pump but being the S/C model there is also a secondary fuel pump and fuel driver module, my first question is where are these located?


my thoughts are is that the car can not monitor the fuel pressure and regulate it as I believe there is not a fuel pressure regulator fitted to the fuel rail and it is controlled by the fuel driver module that controls the secondary fuel pump and possibly the fuel driver module is at fault or bad wire. the previous owner has replaced a fuel pump but I don't know which one, they have also done some very poor wiring (which I have renewed) looks like they have tried to fix an earth problem with the 2 pumps in saddle tank. my second question is which pump is which in the saddle tank being a RHD uk spec car.


If anyone can point me in right direction would be greatly appreciated.

 

Welcome to the forum, when you get a moment stop by our New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum and introduce yourself.

Now...

Both pumps feed to the engine, both are electrically driven. The naturally aspirated cars have a jet-pump to transfer from right to left, but the supercharged cars have two electric pumps, one in either saddle.

The arrangement is that there are hoses connecting the two pumps together, for transferring fuel between saddles, but these are separate to the high pressure outlets to the engine.

Have a look at the pictures of my pumps here https://www.jaguarforums.com/forum/s...-pumps-130587/

Your 70psi fuel pressure is too high if the car is sitting there idling, it should be about 55psi, you should only get up to 70psi if the engine is at maximum boost and load. The pressure sensor is mounted on the fuel rail, left side (RHD passenger side) and has a vacuum/boost line connected to the supercharger outlet, the fuel pressure is mean to be 55PSI above the manifold pressure, so if you have 15PSI boost, the fuel pressure should be up to 70PSI. At idle no boost, 55PSI is where it should be.

The fuel pump driver is incorporated into the REM (Rear Electronic Module) and it recieves a signal from the PCM (Powertrain Control Module, Engine ECU) as to how much it has to spin the pumps to get the right pressure.

Have you checked the fuel filter for blockages? Also check that the vacuum/boost hose to the fuel pressure sensor on the rail is connected. The sensor is a standard Ford item, also used on the turbocharged Focus, and it has been know to blow the diaphragm and read falsely high...

I had some dramas with my XJR a while back, so I had a thorough look into the fuel system on these cars, the STR and the X350 XJR share all the same fuel system...

 

Thanks Cambo, that makes sense and bit clearer on how it all works thank you.
I did think 70psi did seem a little on the high side, would explain why its flagging up with problem but still happy to run. I did read somewhere that someone had the vacuum pipe come off plenum and cause an issue so know the bit you mean. yes I changed the fuel filter as part of a recent service so hopefully its all ok, will pull vacuum pipe and give it a suck tonight see if I can feel any resistance, doubt its too expensive part so may just replace it anyway.


have another question about auxiliary water/SC coolant pump but will post separate thread.

 

Out of the blue I received the dreaded Restricted Performance warning. Checked for codes and found P1338. Checking further I realized I was out of my league. Took the car to my Indy for a solution. The narration on my service report as follows. "Removed fuel pumps and swapped - high current drawn on main pump. may require replacement in the future."
I Called one of the sponsors to this forum to order a replacement pump in case I have a failure and they need to know it I want a left or right pump. I told them it was the primary pump. After several frustrating minutes being schooled on the difference between a one pump car and a two pump car I gave up.
My question to any learned member who would like to chime in, is the primary pump left or right. I would like to have a replacement in case of a failure.
I don't have access to the free download JTSC as I can't get it to load on Win10.
Thanks in advance. Harry.

 

So I have order a new fuel pressure sensor as they are only £43 from jag but in the mean time I though I'd have a look at the wiring. There is a 3 pin plug for the FPS and with the ignition off there is no power to the left or right terminal and the middle one gives continuity to ground (from battery), with ignition on the left and right terminals are both showing 4.8v which I wasn't expecting with it unplugged, I was only expecting 5v ish to one as a reference feed, also with ignition on the ground shows resistance of 151ohms. I've been using wiring diagrams from jagrepair.com which seem very comprehensive but they don't show this FPS anywhere on diag that I can see but my guess is that it feeds back to the ECM which in turn talks to the REM/fuel driver module. also in my checking I found that the ground from fuel driver module gives 15ohms resistance which I'm guessing is not a good thing!


I'll be honest when it comes to spanner work I consider myself to be very competent but electrics are just witch craft to me.

 

It may have several names. IP perhaps?

 

If your fuel pressure sensor is bad it will set a code. I had that happen with my 2005 STR. Your codes are different and point to fuel pump problems. I would follow what Cambo suggested.

Your mechanic does not understand how the STR fuel system works if he used the term main pump. There is no main pump on an STR. Read Cambo's description as the R is different from all other S types.
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Ok so what i've discovered so far is i have 2 problems! the first is someone else's dodgy wiring and the second what they were trying to fix.

The reason for 70psi fuel pressure at idle is because someone has decided to ground both pumps by splicing into Yellow ground wire at pump and earthing it to the body by seatbelt anchors so they run flat out from moment you turn ignition on, my guess is they had a problem and thought this would get pumps running.

So there are 2 pumps, a primary and a secondary both of which have a wiring connector with 4 wires each, Red supplies power and Yellow is ground, the other 2 wires i'm guessing are for float level (fuel gauge works ok). Now the one on the right (drivers side) is controlled\feed power from the REM, this i think is the primary and the one on the left (passenger side) is controlled\feed power from the fuel driver module, this i think is the secondary. Now the way i understand it is that both fuel pumps are switched on and off by their control modules to vary the rate of fuel being delivered to the engine based on signals received from the ECM, this in turn is feed information from other sensors such as the fuel pressure sensor. All of which is to keep a constant fuel rail pressure but with out having to send unwanted fuel back to the tank (as with older style cars that would have a fuel return pipe and pressure regulator).

ok a few questions:
1. What i don't fully understand is why a different control module for each pump, why does the secondary pump need to have a fuel driver module? why not control both from 1 module.
2. In order to vary the pumps speed do the control modules switch the ground supply on\off?
3. I've checked continuity from wires at both pumps back to their relative modules and all is ok, so i don't think the wires are the problem but more than likely one of the modules is bad, if i have to get a replacement REM or FDM will they need to be programmed to the car?

Before i get too carried away i'm going to remove all the extra wiring that's been added and see what runs and what doesn't, will also check the wiring harness for ECM in front passenger bulkhead in case any poor connections, water damage and continuity back to REM.

 

I recall they're PWM so should never be grounded. If you can get it back to how it was designed to be and fix anything broken you'll have a good car.

Workshop manual may have a lot of useful info & tests plus consider OBD or even IDS/SDD.

 

Good work in finding the previous messed up repair! I think you are on the right path now.

1. I don't know but the second pump is suppose to kick in around 3000 rpm and up on the STR. I don't think the second pump even runs until that RPM is reached.

2. The pumps are driven with a PWM signal on the power side. Yes REM sends the PWM signal.

3. Yes the REM for sure will need programming. Not sure about the FDM. Have not heard of the FDM before? Where is it located?
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I believe the driver modules are very simple so won't need any reprogramming. They're known as fuel pump modules in the Electrical Guide.