Non Starter low rail pressure

Jaglad23 · Dec 29, 2023

Hi all
I’m come to this forum as getting no joy on the Jaguar forums, just usually being told to take to Jaguar independent.
Anyway my issue is non starting.
The engine is the 3.0d twin turbo model kicking out 275bhp
A few weeks ago going into work cruising down motorway at 70 when engine fault came on dash and car came to a standstill. Tried to restart but nothing, turned over but wouldn’t fire.
Got AA to recover me home, they checked codes and he said said low fuel rail pressure but didn’t give me full code then he cleared them.
I’ve checked lp pump in tank got good flow to filter, and good flow from filter to hp pump.
When cranking live data shows between 11psi and 15 psi so I’m guessing that’s just from the lp pump.
Thought hp pump had failed so swapped hp pump with another from a good running engine. Still wouldn’t start.
Isolated each injector one by one with a sealing nut on the rail, made no difference rail pressure not increasing. It’s like all the fuel is going straight through the hp pump and up the return line.
What am I missing or what should I be checking.
Thanks

marjon · Dec 30, 2023

Not familiar with the V6 but there should be some sort of Fuel Pressure Regulator on the rail to hold pressure.
If its similar to others then 15psi is nowhere near enough to get it to start.
Do you get a squirt out of the rail when you were doing your testing or does it drop to 0psi.

@gstuart or @tyregeezer may have some documentation to help.
J

Jaglad23 · Dec 30, 2023

marjon said:
Not familiar with the V6 but there should be some sort of Fuel Pressure Regulator on the rail to hold pressure.
If its similar to others then 15psi is nowhere near enough to get it to start.
Do you get a squirt out of the rail when you were doing your testing or does it drop to 0psi.

@gstuart or @tyregeezer may have some documentation to help.
J

There is fuel in the rail but not at the pressure I need, I’m not sure if it drops to 0psi as head was under bonnet while I was putting test but on. I’ll crack an injector pipe and see if it drops, as the lp pump stops running after about 10-20 seconds so what pressure is there should disappear

marjon · Dec 30, 2023

Jaglad23 said:
There is fuel in the rail but not at the pressure I need, I’m not sure if it drops to 0psi as head was under bonnet while I was putting test but on. I’ll crack an injector pipe and see if it drops, as the lp pump stops running after about 10-20 seconds so what pressure is there should disappear

From what I know (TDV8) the rail should hold pressure and its a dam sight more than 15psi. (dont get your face in the way type pressure)
If you have fitted a known good HPFP then its not holding it at the other end (or controlling it electronicky)
Although I would also say 15psi seems pretty low for a LP fuel pump but it could just be cos it has no resistance and going straight through?

Oh and you need to be seeing many bars not low psi.

J

Jaglad23 · Dec 30, 2023

marjon said:
From what I know (TDV8) the rail should hold pressure and its a dam sight more than 15psi. (dont get your face in the way type pressure)
If you have fitted a known good HPFP then its not holding it at the other end (or controlling it electronicky)
Although I would also say 15psi seems pretty low for a LP fuel pump but it could just be cos it has no resistance and going straight through?

Oh and you need to be seeing many bars not low psi.

J

Yea should be about 300 bar running pressure, I think it’s about 150 bar to start it so well down.
I’m guessing something is passing somewhere or something has failed electronically

Graculus · Dec 30, 2023

Firstly, check you are getting fuel up to the HP pump from the LP side - and at what pressure, don't rely on measured values unless you know which sensor you've viewing.
If you have the correct LP value (15psi / ~1 bar is too low) at the inlet to the HP pump, check the supply voltage to the fuel solenoid on the pump, if OK, check the fuel rail pressure sensor supply voltages, if OK, check the pressure control valve supply voltage.
There is a return line from the PCV, briefly clamping this off during cranking will show if it's open or closed (it should be fully closed with FRP <150bar. In general, actuators have battery voltage supplies, sensors have 5V (+/- 0.25V) supplies, don't forget to check the ground connections.

It's too big a scope to list every possible test, you need to confirm good low pressure fuel first - look for 4-6bar at the HP pump inlet and go from there.

Jaglad23 · Dec 30, 2023

Graculus said:
Firstly, check you are getting fuel up to the HP pump from the LP side - and at what pressure, don't rely on measured values unless you know which sensor you've viewing.
If you have the correct LP value (15psi / ~1 bar is too low) at the inlet to the HP pump, check the supply voltage to the fuel solenoid on the pump, if OK, check the fuel rail pressure sensor supply voltages, if OK, check the pressure control valve supply voltage.
There is a return line from the PCV, briefly clamping this off during cranking will show if it's open or closed (it should be fully closed with FRP <150bar. In general, actuators have battery voltage supplies, sensors have 5V (+/- 0.25V) supplies, don't forget to check the ground connections.

It's too big a scope to list every possible test, you need to confirm good low pressure fuel first - look for 4-6bar at the HP pump inlet and go from there.

Ok thanks for that, is it best to check voltages with a meter or see if it’s giving a reading on the live data (not sure if it does).
I could be wrong but I’m sure the lp pump on the Jag produces between 0.5 and 1 bar of pressure

Graculus · Dec 30, 2023

You could be right - the 2.7 TDV6 has that spec., I had it in my head that the EU5 had a higher pressure 'for emissions reasons', the marque I work for currently certainly has a higher LP side on EU5 vehicles - as do most, 1bar is quite 'lethargic' TBH, of course, the flow rate is just as important, as is lack of air in the fuel! IIRC there is a temperature sensor on the injector leak-off pipe that had a habit of causing problems, although that may have just been low power, not no power.
Always check voltages with a meter, don't rely on live values unless you've confirmed them accurate first.

You say the AA cleared the DTC's (I hate it when they do that!), have you re-read to see if any have come back? quite a lot won't appear until the engine is running but if there are any, it'll point to a fundamental issue.

Jaglad23 · Dec 30, 2023

Graculus said:
You could be right - the 2.7 TDV6 has that spec., I had it in my head that the EU5 had a higher pressure 'for emissions reasons', the marque I work for currently certainly has a higher LP side on EU5 vehicles - as do most, 1bar is quite 'lethargic' TBH, of course, the flow rate is just as important, as is lack of air in the fuel! IIRC there is a temperature sensor on the injector leak-off pipe that had a habit of causing problems, although that may have just been low power, not no power.
Always check voltages with a meter, don't rely on live values unless you've confirmed them accurate first.

You say the AA cleared the DTC's (I hate it when they do that!), have you re-read to see if any have come back? quite a lot won't appear until the engine is running but if there are any, it'll point to a fundamental issue.

I’ll get the meter on it in the morning.
And I’ll have a look around for temp sensor on the leak offs.
I’ve tried reading codes again but nothing is coming up. Is it worth giving a squirt of brake cleaner to fire up or not worth it as the injectors won’t operate as there’s not enough pressure to make them fire. Was hoping to fire up to throw some codes up

marjon · Dec 30, 2023

As I said earlier. There will be a regulator and the end of the rail. If the hpfp is good then it’s probably go straight out.

J

Graculus · Dec 30, 2023

Firstly, don't unplug any piezo fuel injectors with the engine cranking or running, you can kill them and / or the piston.
Have you the means to carry out a 'lift pump reset'? this usually occurs when the tank has been run low on fuel or the rail pressure is below the 'danger' threshold. The HP fuel pump is locked out along with the injectors to prevent it running dry and causing damage due to the molecular-level clearances required to get the fuel pressure up to 300bar. if you have fuel pressure up to the HP pump, can you backprobe an injector on AC volts to see if there's activity?

marjon · Dec 30, 2023

Graculus said:
Firstly, don't unplug any piezo fuel injectors with the engine cranking or running, you can kill them and / or the piston.
Have you the means to carry out a 'lift pump reset'? this usually occurs when the tank has been run low on fuel or the rail pressure is below the 'danger' threshold. The HP fuel pump is locked out along with the injectors to prevent it running dry and causing damage due to the molecular-level clearances required to get the fuel pressure up to 300bar. if you have fuel pressure up to the HP pump, can you backprobe an injector on AC volts to see if there's activity?

As much as I can see some good info in your posts, some of it sounds very, “AI” or lost in translation.

Lift pump reset ??
How can you lock out the HPFP it’s mechanical isn’t it ??

J

Jaglad23 · Dec 30, 2023

Graculus said:
Firstly, don't unplug any piezo fuel injectors with the engine cranking or running, you can kill them and / or the piston.
Have you the means to carry out a 'lift pump reset'? this usually occurs when the tank has been run low on fuel or the rail pressure is below the 'danger' threshold. The HP fuel pump is locked out along with the injectors to prevent it running dry and causing damage due to the molecular-level clearances required to get the fuel pressure up to 300bar. if you have fuel pressure up to the HP pump, can you backprobe an injector on AC volts to see if there's activity?

What do I need to do the lift pump reset?
I can get meter on injector tomorrow but I’m assuming I won’t get any readings as there isn’t enough pressure in rail for injectors to operate

Jaglad23 · Dec 30, 2023

marjon said:
As much as I can see some good info in your posts, some of it sounds very, “AI” or lost in translation.

Lift pump reset ??
How can you lock out the HPFP it’s mechanical isn’t it ??

J

It is mechanical yeah, driven from camshaft, but maybe electronically a valve opening and bypassing fuel back to tank?

Graculus · Dec 30, 2023

marjon said:
As much as I can see some good info in your posts, some of it sounds very, “AI” or lost in translation.

Lift pump reset ??
How can you lock out the HPFP it’s mechanical isn’t it ??

J

Mechanical, yes, but electrically controlled.

The other comment, whilst slightly patronising, I have no idea what you're on about.

Graculus · Dec 30, 2023

Jaglad23 said:
What do I need to do the lift pump reset?
I can get meter on injector tomorrow but I’m assuming I won’t get any readings as there isn’t enough pressure in rail for injectors to operate

The injectors will trigger regardless of fuel pressure - unless they're locked out. The 'lift pump reset' is poorly named in this context, most diagnostic tools will have the ability, for older LR I use Autologic which will work on Jaguar too.

These might help.

Jaglad23 · Dec 31, 2023

Checked some voltages today got 7.8v at the pcv and the volume control valve on the hp pump. What I did find was the pcv wouldn’t operate at this voltage but does with 12v supply. Is this a voltage too low or a faulty pcv?

Graculus · Dec 31, 2023

The PCV is operated by a PWM signal so may be correct, putting 12V to it will cause it to fully open (or close, can't remember which) I think you need to check upstream of that and have a look at the HP pump control, what is the voltage during cranking?

marjon · Jan 1, 2024

Graculus said:
Mechanical, yes, but electrically controlled.

The other comment, whilst slightly patronising, I have no idea what you're on about.

Well if I upset you then I will take it as a translation issue. But then **** happens and we all get over it.

So I see you have posted a couple of docs.
Could you post the "fuel charging controls " section, I find that as much help as the 1 you have posted. Also the wiring dia is helpful to see the PCV and volume valve work together and are actually interlinked.

I have recently posted them both for the TDV8 and so far the working principle and logic seems similar.
But I have still to come to terms with the, "fuel pump lock out" & "lift pump reset".

Happy new year to you both.

J

Jaglad23 · Jan 1, 2024

marjon said:
Well if I upset you then I will take it as a translation issue. But then **** happens and we all get over it.

So I see you have posted a couple of docs.
Could you post the "fuel charging controls " section, I find that as much help as the 1 you have posted. Also the wiring dia is helpful to see the PCV and volume valve work together and are actually interlinked.

I have recently posted them both for the TDV8 and so far the working principle and logic seems similar.
But I have still to come to terms with the, "fuel pump lock out" & "lift pump reset".

Happy new year to you both.

J

The wiring diagram would be helpful I agree. I’m thinking my pcv could have failed open and the fuel
Is returning to tank as that’s why it won’t build pressure.
Happy New Year

Non Starter low rail pressure

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