Merrion1,

I have read through the thread you linked there once but will read through it again a couple of times, there's a lot of interesting stuff in there, thanks. The final solution for Cambo's pinging seems to have been new cats, with the REM code P1235 being mentioned mid thread, but the discussion of this seemed to trail off somewhat. Although he did replace a lot of stuff along the way including both fuel pumps with the oem jag ones (buckets, pipes and all) which are an eye watering price.

Don,
I looked in the powertrain section of the workshop manual again and can't find any reference to P1235 (P1234 and then P1236 were there, but P1235 isn't !!) I did this by searching the PDF so could have missed something. The bit about P1235 that I put in my recent post was something I found in the electrical section of the manual but there are no pinpoint tests identified that I can find so far that refer to P1235.

I drove for a while today with the scanner showing live figures for fuel level 1 (FL1), fuel level 2 (FL2), pump duty cycle (PDC) & pump duty cycle 2 (PDC2). Driving at around 60mph for about 10 minutes and the figures changed as follows;

FL1 started at 74% and dropped to 80% by the end of the drive, FL2 started at 58% rose gradually to 52%. So fuel level on the right hand side rising and fuel in the left hand side dropping as I drive, that's for certain.

PDC/PDC2 at idle as before 26%/52% (give or take 2 decimal places)
PDC/PDC2 cruising at 60mph 29/58% (give or take 2 decimal places)

When I turned off the engine;
PDC/PDC2 74.9%/0%
This are the same values as when I floored the accelerator in the garage (or maybe very shortly afterwards)

I also looked at live data for the ECM and found one item for the signal from the ECM to the fuel pump(s). It was around 26% at idle, same as PDC on the REM. I cant look at the ECM and REM simultaneously but they seems to be very close or the same. So I'm wondering are PDC/PDC2 the PWM signals to Pump 1 and Pump 2 or is one the signal from the ECM (PDC) and the other (PDC2) the 'doubled' signal from the REM to both pumps?

Looking at Engine Management wiring diagram it shows;
1. a cable from the ECM to the REM (White/Red)
2. two cables from the ECM to FUEL PUMP 2 module, (White/Blue & Yellow)
Two connectors en route in each wire.
So a first step is to check continuity/resistance of these, the connectors to the REM and FUEL PUMP 2 module and associated earths.

I am considering starting a separate thread on the PWM signal used to control the fuel pump outputs and maybe somebody could hook up a carsoft i930 to their car and see if my figures are normal or not? I have searched and read all I can find but still not sure exactly what I'm looking at on the scanner (PDC and PDC2) and whether it's normal or not or relevant to my problem!
ARGHHH!!

 

Jaguar issued some TSBs years ago.

bob

 

Hi Bob
I had the fuel gauge senders and pumps out and bench tested the sender resistance according to the jag TSB.
The left sender tested OK, the right had a bit of a blip in the resistance reading while sweeping the float arm so I replaced this one.
Both pumps ran OK on the bench with 12v applied.
Reassembled and reinstalled the buckets etc after cleaning the internal and external sock filters
Unfortunately I still have the problem.

 

Hi Chris,

Isn't that helpful that P1235 is omitted! The pinpoint tests G251562p3 that apply to P1234 and P1236 should probably also apply to P1235.

You don't have DTCs P008700/P008800 and P0192/P0193, which also deal with fuel pump drive and fuel pressure regulation, but it might be worth at least looking at the pinpoint tests G552275p6 and G206886p2, which involve measuring voltages and resistances at the Fuel Rail Pressure sensor electrical connector, just to rule out a problem with the FRP sensor circuit. Also, with your i930 you can watch the fuel rail pressure indicated by the FRP sensor. The pressure should be around 55psi under most conditions, rising to 70psi or so under hard acceleration, then dropping again, sometimes into the 40s, then back up to around 55psi.

Cheers,

Don

 

This from a Fixya answer re Fords.


Electronic Returnless Fuel Systems (ERFS) utilize a Fuel Pump Driver Module (FPDM) to control fuel pressure. The PCM uses a Fuel Rail Pressure Sensor (FRP) for feedback. The PCM outputs a duty cycle to the FPDM to maintain the desired fuel rail pressure. During normal operation, the PCM will output a FP duty cycle from 5% to 51%. The FPDM will run the fuel pump at twice this duty cycle, e.g. if the PCM outputs a 42% duty cycle, the FPDM will run the fuel pump at 84%. If the PCM outputs a 75% duty cycle, the FPDM will turn off the fuel pump.

If the FPDM does not out any diagnostic signal, (0 or 100% duty cycle), the PCM sets a P1233 DTC. This DTC is set if the FPDM loses power. This can also occur if the Inertia Fuel Switch is tripped.

If the FPDM outputs a 25% duty cycle, it means that the fuel pump control duty cycle is out of range. This may occurs if the FPDM does not receive a valid control duty cycle signal from the PCM. The FPDM will default to 100% duty cycle on the fuel pump control output. The PCM sets a P1235 DTC.

If the FPDM outputs a 75% duty cycle, it means that the FPDM has detected an open or short on the fuel pump control circuit. The PCM sets a P1237 DTC.

This will give you an idea of what's involved on a Ford:

https://www.justanswer.com/ford/1e3h...gini-lite.html

 

In the Jaguar implementation, the FPDM for fuel pump 1 is built into the REM, and the FPDM for fuel pump 2 in early S/C cars is known as the Fuel Pump 2 Module, mounted behind the REM.

Cheers,

Don

 

Just to give an update on this;

In my earlier post detailing the readings from my carsoft i930.
I'm pretty sure that the two percentages that I was seeing are
1. the signal from the ECU to the REM and
2. the signal from the REM/Fuel pump 2 module out to the fuel pumps
and both are behaving normally after reading the great links posted by meirion1.

I took out both the REM and the Fuel pump 2 module and cleaned all the connectors and earth connections on the right hand side of the boot where they are located.
Also cleaned the connectors to the fuel pumps which I didn't do when I had them out.
Also listened to the operation of the pumps using a screwdriver against the top of the units under the back seat. I can hear both pumps running, they sound the same, give the throttle a good bit of gas and you hear them increase in speed then cut out as the max fuel pressure is reached, then cut in again immediately afterwards.

My conclusion at this point is that as indicated by the original fault code displayed on the IC that I have a jet pump fault. So in the right hand pump unit/bucket I think the nozzle that induces flow to the right hand side of the tank is blocked, resulting in low or no flow to the left hand side of the tank.
So when I next get the chance I'll take out the right hand side pump bucket and see if I can clean the nozzle.
In the meantime I'm just filling up when the gauge hits the halfway mark and everything's running well.

 

So another update to this thread

I've had both fuel pump modules out again.
Last year I concluded that the jet pump in the right hand module that transferred fuel to the left hand side of the tank was blocked.
Not so I'm afraid, the jet pump nozzle was clear.

Getting code P1235, stored in the REM, which is the signal from the ECM to the REM which drives the right hand pump, P1235 is that the signal is out of range and low. Checked all the other wiring between the REM and the right hand pump and the left hand pump and the second fuel pump driver module fitted to the xjr.

The pinpoint tests for P1235 are for the wire between the ECM and the REM, and if it's not this the manual says the ECM is at fault, which seems very unlikely??
So got to the ECM connector but couldn't go any further as I didn't have a 5 point torx bit, so had to put it all back. But I'll have another go at testing this wire this weekend.
Car is running OK but need to see of there's any hesitation at WOT.

I'm suspecting if it's not the wiring between the ECM and the REM the right hand pump is on the way out. Then there's the issue of sourcing two suitable replacement pumps.. Phew!

 

Tonight I removed the back seat and plastic covers over each fuel pump to take some readings with a DMM for each pump, left and right to see if there was any difference with a view to establishing a problem with either of the power feeds;

Measured voltage across the pump connections by back probing at the pump connector;
Ignition switch on, no voltage
Engine start, voltage peaks up to 13V and then settles down to approx 6.85 volts.
car is in the garage, give the throttle a blip and the voltage rises momentarily to over 7 volts, then back to 6.8 volts at idle
Exactly the same for the right and left hand pumps, no difference;


Then I switched the meter to duty cycle;



And it showed 53% at idle
Blip the throttle and it rose to around 69-70%
Then settled back down to 52-53%
Exactly the same for the right and left hand pumps, no difference;

So I'm investigating the code P1235 (pump control signal from the ECM is out of range and low) in the REM which supplies the right hand pump.
There seems to be no difference in the power signal to either pump, the left hand pump is supplied by a separate and second fuel pump driver module in the early xjrs.

These readings were taken with the car in the garage with no real load on the engine and I have no idea whether the voltage and duty cycle readings I recorded are 'normal'.

As the power to the pumps is PWM are the voltages shown on my simple DMM an average of the on and off periods, ie the pumps are getting around 12v but only for 53% of the time resulting in an average voltage of (applied voltage) x (duty cycle/100) being shown on the meter?

 

Have you tried ENGINEERING TEST MODE?

You can 'see' the level sensors individually as the INST PK 'sees' them.

Many more parameters included in the test mode.

bob

 

Hi Chris,

Here are the definition and possible causes of P1235:




According to the manual, ECM failure is a possibility, but it seems more likely that P1235 is caused by an issue with the pump drive electrical circuit, which could include a problem in the the wiring, a loose or intermittent electrical connection, or a problem inside the fuel pump motor itself.

Did you ever look at the pinpoint tests for P1234 and P1236 to see if they might be applicable to P1235?

I would think that one easy test would be to check the resistance to body ground between each of the wires at the fuel pump electrical connector to see if you find any low resistance readings (say, 5K ohms or less). You could also measure between each of the wires for low resistance indicating a possible short somewhere in the harness.

Cheers,

Don

 

Bob

Yes I've been looking at the fuel senders using engineering mode on the Instrument Cluster and it confirms the level in one side of the tank drops at a much greater rate than the other.

 

Don

I've tested all the wiring save the wires running from the ECM to the REM and the second Fuel pump Module.
I got as far as the ECM connector but didn't have a 5 point torx to remove it.
I have one now and am going to try to finish off testing the wiring according to the pinpoint tests for P1234 and P1236 this weekend

 

Ok so I've just finished the pinpoint tests for codes P1234 and P1236. I had code P1235, but there are no pinpoint tests for this code. P1235 has not reappeared in the last few days since I cleared it.
So all the tests on the wiring were positive, no lack of continuity between the ECM and the REM on the pump control circuit, no short to ground or B+.

So, the manual says possible ECM failure but none of my investigations so far point to that. The electrical signals to the pumps from the REM and FPM I monitored and reported in post 29 seem to be OK as far as I know. The only thing that would be good to know is what duty cycle should I have at idle? I measured around 50%.

So I've checked out pretty much everything I can on this. Now I'm concluding that the right hand pump is knackered although I can hear it running and have had it running out of the fuel tank in a bucket of petrol and it pumped fuel.
So I suspect that the left hand pump is doing all the work and transferring fuel to the right hand side via the jet pump and transfer pipe. Right hand pump is running but is not transferring any fuel to the left hand side so the fuel level is dropping quickly in the left hand side and staying at full on the right hand side. (which is what I am seeing from monitoring the left/right hand fuel senders). The result of this is that the fuel gauge gets to half full then drops to zero when there is no fuel in the left hand tank and I get a fault code for jet pump failure in the IC.

Is there anything I'm missing here?
It's driving me nuts.
Any comments very welcome.
The schematic of the early xjr fuel system is shown in post 7 of this thread for anybody who's interested.

The only thing that would be really useful to know is what duty cycle should I have at idle to the pumps from the REM/FPM? I measured around 50%.
If my suspicions are true that only the left hand pump is delivering fuel to the rail then on a car with both pumps working properly it would only need to be half of this, ie around 25%.
Anybody get an early xjr with the two pump set up willing to read the live data on the REM using their scantool to see what the duty cycle signal to the pump is at idle??
I'd be very grateful and you might have a hand in saving me from the madhouse!

 

Hi Chris,

From post #20 in this thread - from the research I had done, it appears that the duty cycle from the ECM has a range of 4-51%, which is doubled by the REM so you would expect 8-100% if that is the signal you are measuring. Your 50% at idle may be about right - I would assume that a duty cycle of 8% would be under overrun conditions or possibly at WOT when the injectors are cut off.

Cheers,

Don

 

Hi Don,

Yes I agree, the 50% duty cycle I measured could be right, but on the other hand it might not be!
I'm pretty sure that the pump flowrate is directly proportional to the PWM signal.
I don't know but would have thought that the fuel flow demand at idle would be less than half of that required at WOT?
It would be useful if somebody with a two fuel pump xjr could look at the duty cycle signal from the REM at idle either on a scantool (the carsoft will do it) or by back probing the power supply to the pumps at the connectors to one of them or at REM connector.

 

The pump pressure is NOT the only determining factor in fuel/air ratio.
The injector pulse width is the ultimate arbitrator. Fuel pressure can rise and the pulse width can narrow to get the same amount of fuel through the injector.
The ECM just performs a 'balancing-act' between the two.

bob

 

So another installment on this problem.
Having checked out all the wiring according to the pinpoint tests associated with code P1234, 1235 & 1236 went back to basics;
Cleared the code P1235 and it didn't reappear.

1.
Checked the level senders on the left and right hand side of the tank by cross checking the RAW 1 & RAW 2 values in Engineering Mode on the IC against the resistance of the senders at the pump connectors and against the % level readings on the REM for Fuel Level 1 & 2 on my scan tool.

So I discovered that all along I have been getting the left and right fuel sender readings the wrong way round.
RAW 1 on the IC is the LEFT hand of the tank, RAW 2 is the RIGHT hand side of the tank
Fuel level 1 read on the scantool from the REM is the LEFT hand of the tank, Fuel level 2 is the RIGHT hand side of the tank.

For the last year I had assumed that the RAW 1 was the same side of the tank as Pump 1.. silly me. So all along I've been blaming the right hand pump when all along the left hand pump has been the culprit.

2.
I checked the level in both sides of the tank and then ran the engine at idle for 10 minutes and got the following results;
Start: Left 67% Right 58%
After 10 mins: Left 93% Right 44%

I turned off and let the fuel settle in the tank for 20 minutes. This allows the levels in the two sides to even out due to siphon effect as they are connected by the transfer pipes in the tanks;

I checked the level in both sides of the tank again, then disconnected the left hand pump electrical connector, started and ran the engine at idle for 10 mins;
Start: Left 67% Right 58%
After 10 mins: Left 93% Right 44%

I turned off, reconnected the left hand pump and let the fuel settle in the tank for 20 minutes.
I then checked the level in both sides of the tank again, then disconnected the right hand pump electrical connector, started and ran the engine at idle for 10 mins;

Start: Left 67% Right 58%
After 10 mins: Left 65% Right 59%

So the car runs fine, peddle to the metal and it goes like a train. car starts and runs fine with either just the left or just the right hand pump connected. Both pumps are working and running OK.
BUT the LEFT hand pump is not transferring any fuel to the right hand side which results in the right hand side becoming empty when the left is still full, fuel gauge drops from half to zero.

So I've had the pumps out twice so far but have always concentrated on there being something wrong with the right hand pump.
Also again after a year of pondering this one have only just noticed a label on top of the right hand pump with a 2004 date on it when the car was registered in 2003!. The same label on the left hand pump has a 2003 date on it. So the right hand pump has been replaced..

So I'm going to get the left hand pump out AGAIN and see of I can spot anything inhibiting the jet pump action that is not working.
The problem is with the left hand pump/transfer mechanism NOT the ECM.
Its possible that if its not a physical blockage then the left hand pump is failing but still has enough life left so that the car runs OK.
One thing I have noticed from driving around and watching the RAW 2 (right hand tank level) drop is that if I floor it this does seems to transfer some fuel from the left to the right side. This could be due to the fuel being pushed back in the tank and flowing over the center of the saddle rather than the pump transferring the fuel.

So I'll get the left hand pump out again and report back.
I think I'm on the verge of solving this ... about time.

 

Hi Chris,

I haven't thought this through like you have, but it does seem that your symptoms could be caused by an obstruction in the left-to-right crossover line, or an obstruction of the suction jet pump inlets on the bottom of the left pump module. I can't remember if you have tested that crossover line for free flow. Could another suspect be the parallel pressure relief valve in the left-to-right fuel delivery line?

On an '06 XJR I worked on (single pump), I found that one of the hoses from the left tank was kinked in the saddle area over the driveshaft tunnel where it could not normally be seen. I put a hose clamp at the point of the kink to force the hose back into round and that seemed to do the trick.



Another thing I'm trying to ponder is whether a problem with the ORVR/EVAP system could cause your symptoms. Have you looked into the operation of that system? Could a pressure or vacuum problem cause your symptoms? I assume the fuel tank pressure sensor signal can be read via Live Data - have you checked for any unusual behavior?



Sorry for the wild guesses and if you've already covered these questions. Just hoping to prompt some line of inquiry that may help.

P.S. The above diagrams are from the Technical Guide, which you can download at the link below if you don't already have it:

Jaguar X350 Technical Guide 2004

Cheers,

Don

 

So an update on my problem.
I got hold of a pair of used early xjr pumps from Ebay
Put them in today
And same old problem. All the fuel gets pumped over to the left hand side of the tank. No transfer is taking place from left to right.

So .... it's not the pumps and I now have a good set of spares that I don't need!! At least I have eliminated the pumps as the cause. The set of used pumps cost me 350 euro but I suppose I can sell them on. They seem to all go for this amount or more.

Next port of call is the fuel pump driver module that feeds the left hand pump. Then the REM, then the ECU
Does anybody know if the fuel pump module on the xjr needs to be programmed?
Also I am assuming that if I find a used REM it will need to be programmed to the car, am I correct?