Sport Fuel pressure problems

2010 3.0L Diesel L320

Been having fuel pressure problems for a few weeks now.

It started on the motorway and went into limp mode.

When home I got the code and it was - fuel rail pressure too low.

This morning I have changed the following parts
- Fuel filter
- Fuel pressure sensor
- Fuel pressure regulator

Now, I am getting the opposite code (P0088-17) Fuel rail pressure too high!! (quite frustrating) - and it is consistently doing it, if you clear it, comes back a few minutes later and it is always too high now - which is never was before this morning.

I am right in thinking the probably cause of this is the high pressure fuel pump or am I missing something?

Also if that is the only possible problem - i seem to remember reading somewhere it is a body off job!?


Thanks

Are there any leaks around the engine for diesel?
Try some good injector cleaner and see if there are any changes. Rail pressure can be down to a sticking Injector also. Jamming internally.

Mark Piercy said:

Are there any leaks around the engine for diesel?
Try some good injector cleaner and see if there are any changes. Rail pressure can be down to a sticking Injector also. Jamming internally.

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But he now says he has pressure too high?

Hope u dont mind me asking but in that case has the fuel filter connections been put back correctly

also should be able to test the LPFP at the shrieder valve at the back of the engine when the ign is turned on

Datatek said:

But he now says he has pressure too high?

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Also an effect of an injector not opening fully when it should. The fuel pump pressure control valve can also give issues if it sticks open longer than it should. Live data could help to verify the requested pressure and the actual pressure.
The rail pressure sensor can also give a false reading.

Mark Piercy said:

Also an effect of an injector not opening fully when it should. The fuel pump pressure control valve can also give issues if it sticks open longer than it should. Live data could help to verify the requested pressure and the actual pressure.
The rail pressure sensor can also give a false reading.

Click to expand...

Thank you, every day a learning day

Sorry for the delay in response. Have only just now had a quick chance to look at it again.

@Mark Piercy - No leaks around the engine I can see. I did have a leak from the bottom of the filter where the sensor screws in because the thread was cracked but thats sorted now. Would a sticking injector not through a code of its own?

There is actually already some injector cleaner in the tank and has been run for quite a while with it - not sure if it was a good one or not!! (Nitrox Diesel Power clean)

I will try and get some live data for you tomorrow after work.

@gstuart - I didn't take any of the connections to the filter off - it just twists onto its housing, however I have double checked they all looked fine. How much pressure am I expecting to be coming out of that valve? I will take a look at it.



Some more information. I took it for a drive today, had the code on the entire time to it had reduced performance. For the first 20 minutes it behaved completely normally for a car in Limp mode (pulled off ok in first and got up to 30 with little problem but after that didn't really have much power)

However after about 20 minutes it just stalled when I was trying to pull off. On restarting I could move about 5 metres and it would stall again, the revs would just go down until it couldn't keep running. At this point I was about 150m from my house and it took me over 20 starts to get home.

Then after sitting on the drive for 5 minutes I thought I would have another go and magically it was back to behaving like a normal car in limp mode.


Thanks for your help all.

lj5000 said:

Sorry for the delay in response. Have only just now had a quick chance to look at it again.

@Mark Piercy - No leaks around the engine I can see. I did have a leak from the bottom of the filter where the sensor screws in because the thread was cracked but thats sorted now. Would a sticking injector not through a code of its own?

There is actually already some injector cleaner in the tank and has been run for quite a while with it - not sure if it was a good one or not!! (Nitrox Diesel Power clean)

I will try and get some live data for you tomorrow after work.

@gstuart - I didn't take any of the connections to the filter off - it just twists onto its housing, however I have double checked they all looked fine. How much pressure am I expecting to be coming out of that valve? I will take a look at it.



Some more information. I took it for a drive today, had the code on the entire time to it had reduced performance. For the first 20 minutes it behaved completely normally for a car in Limp mode (pulled off ok in first and got up to 30 with little problem but after that didn't really have much power)

However after about 20 minutes it just stalled when I was trying to pull off. On restarting I could move about 5 metres and it would stall again, the revs would just go down until it couldn't keep running. At this point I was about 150m from my house and it took me over 20 starts to get home.

Then after sitting on the drive for 5 minutes I thought I would have another go and magically it was back to behaving like a normal car in limp mode.


Thanks for your help all.

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the mechanical side of the injector can stick or be blocked and the ecu cant sense this. this is when a possible high or low rail pressure case can happen. a leak off test on the injectors can reveal any physical issues.
the test has to be done on all the injectors at the same time to measure the fuel being returned to the fuel system. this can be done on the vehicle. any difference in the fuel return from any one or more injectors will result in a or all injectors to be replaced. the fuel return quantities should all be very similar.

Both high & low faults at same time is usually the pressure sensor ?

I am no expert, but if you had low pressure then changed sensor and now have high pressure, surely you should be looking at the new part?
Genuine or copy part?

Genuine Bosch part.

I’ve just plugged in the genuine Land Rover diagnostics tool.

It’s telling me it’s a short on the fuel pressure sensor circuit.

I’m not an electrician and have no idea how to actually locate a short but going to do some googling

So, there is no short on the pressure sensor circuit.

3 wires…
1 power - 4.99 volts
1 ground - it is a good ground
1 signal - 0.81 volts

Not sure what voltage the signal should be from the sensor.

Really annoying because I thought that was going to be it.

Wiring diagram below

lj5000 said:

So, there is no short on the pressure sensor circuit.

3 wires…
1 power - 4.99 volts
1 ground - it is a good ground
1 signal - 0.81 volts

Not sure what voltage the signal should be from the sensor.

Really annoying because I thought that was going to be it.

Wiring diagram below

Click to expand...

The return signal is usually between the 5v power.
never 0v or 5v.

somebody maybe able to come up with a volts v pressure graph.
was that reading taken at the sensor with engine running or not running? Or was it taken from the end of a long loom at another plug?
how did you get the signal reading? Did you piggyback into a plug somewhere?

J

It was take about 10cm from the plug that goes directly into the pressure sensor… I have a needle attachment for my metre so just when straight into the wire

Have you tried the same at the ecu?
ground is good, power is good. But is the signal v the same getting back.

engine running or not when you did the test?

J

Engine running.

I’ve just swapped the sensor back to the original (as I changed 3 parts at one I’m not sure anything was wrong)

I’m now getting a different fault code (see picture) it will not clear at all.

Voltage on signal is now 4.66. Measured at same point with engine running.

I’ve come inside now to do some more reading but when I’m out again I will read at the other end…

lj5000 said:

Engine running.

I’ve just swapped the sensor back to the original (as I changed 3 parts at one I’m not sure anything was wrong)

I’m now getting a different fault code (see picture) it will not clear at all.

Voltage on signal is now 4.66. Measured at same point with engine running.

I’ve come inside now to do some more reading but when I’m out again I will read at the other end…

Click to expand...

As your code reader is now showing a different fault.
to me 4.6 is probably on the upper end of what I would expect on a 5v sensor. As was .81v on the lower range.
but as your reader is seeing a different fault then the loom could be ok, (my thinking) ?

I need to read a bit more, but as you have changed your fuel regulator as well have you/can you check fuel pressure with a proper gauge?

J

Unfortunately I don’t have a pressure guage that can read this.

The loom is fine in every measurable way using my multimetre. All continuity is perfect to the ECM, no signs of a short on any of the 3 wires.

It’s weird the fault has changed, to me it says one sensor is dodgy (probably the old one that’s in now) but I’m not sure.

From the start, I was thinking it’s the high pressure fuel pump so I started replacing cheaper, easier parts mainly in hope. And it’s clearly having an effect. There’s this and also the problem originally started with a low fuel rail pressure code so now I’m not so sure.

lj5000 said:

From the start, I was thinking it’s the high pressure fuel pump so I started replacing cheaper, easier parts mainly in hope. And it’s clearly having an effect. There’s this and also the problem originally started with a low fuel rail pressure code so now I’m not so sure.

Click to expand...

From your readings 1 of those sensors is duff (any sane person would think that).
As I said maybe somebody can come up with a graph, high v don’t always mean high pressure so I am not sure which way they work.

hope @gstuart may have some files to help you.

reading the pressure on a good ole fashioned gauge would probably help a lot to be honest.

J