Thread: LR3 2006 4.4ltr, fuel issues which Land Rover cannot diagnose

Hmmm, the fuel tank replacement is a bit of a story:

I first tried to clean out and back-flush the original pump and halo-filter -- which was a moderate success. I replaced the pump into the tank, and then installed the tank back into the vehicle. This was the first effort made after the flooding.

The original pump ran up and was measured as delivering 80ps from an external gauge fitted inline with the fuel rail. This powered the vehicle for about 10 minutes on its first test drive but began to run lean and stumble. I first thought that this was caused by a shortage of fuel (hence the fuelling up), but after filing up with gas (petrol) at the fuel station, she stalled on her way out of the station. After the vehicle quit on me in the middle of lights, she started back up again after a few seconds but turning off the key and turning it back on again (though I did not know I was resetting anything at the time). She only had enough power to get me back to the shop. The following morning, we tried the car again, and she started and drove fine and we again tested the vehicle with the fuel pressure gauge inline. The gauge read 80psi, but as the vehicle started to become lean, the fuel pressure gauge lost pressure. However, all this happened within the first 5 minutes, and while still in the yard. We presumed the pump repair and cleaning had not gone well, and sought a second pump.

Sourcing a second hand fuel pump was possible and I found a 2006 donor, but when the tank arrived, it was clear that the pump and tank were different. The donor vehicle had been fitted with a 2010 tank and pump after a recall was issued on certain vin numbers. We were given the entire tank, fuel pump, electric harness and all of the evap. pipes and fuel lines. It is this tank and pump (which are not interchangeable) which is currently fitted to the vehicle -- not the original tank. The donor tank was placed into the vehicle and the fuel pressure was inspected before the vehicle was taken out of the shop; the inline fuel pressure gauge measured 80psi at idle in neutral. It is possible that the gauge is slightly out, but not excessively as it is a Snap On kit.

What is interesting from all of this, is that the first tank and cleaned pump, presented with similar symptoms (but more severe and happening sooner) than the second tank. The second tank was selected also, in part, due to the difficulty of washing out the first tank to remove the clay like sediment which would be in all of the weird baffles and plastic tubes shown in your diagram above.

Of further interest:

Tonight's test run was conducted with little fuel in the tank, and after re-cleaning the throttle body and the MAF sensor. It was only 15 degrees outside and the vehicle drove seamlessly for 50 miles without any fault presenting. However, coming into the next town the vehicle started faintly hesitating, and I turned around only for the vehicle to quit on me fully as I accelerated out of the town on the highway. Having switched off the vehicle and re-started it, I was able to drive 50 miles home before any further symptoms presented. The fuel temperature reached 63degrees, and the ECM temperatures were also normal -- The only difference between tonight's and last night's test runs, are the external temperature, and the cleaner MAF sensor -- yet last night I struggled to drive 25km after 10 minutes idling, and tonight I idled for 20 minutes and drove 80km before symptoms occurred.

I hope this information is helpful to you all -- though I am sensitive to your position on too greater fuel pressure, I find it difficult to understand why too much pressure (which is maintained by the pressure regulators inside the tank and pump) would sometimes permit the car to drive for 2 hours or more, and sometimes only 25 minutes.

There does seem to be an ambient air temperature correlation: The more fuel in the tank, the longer the time taken for issues to present. The colder the ambient air, the longer it takes for symptoms to present.

After speaking to a friend in the UK, I have ordered a new MAF sensor (hence the re-cleaning tonight) -- but after tonight's performance, I am reluctant to believe it is the MAF. Indeed, I have ordered a CPS as well as a MAF, but I cannot actually source any other relevant sensors in the US other than the throttle position sensor (which I am reluctant to try at $591).

Originally Posted by Cambo351

I suppose there isn't a pressure sensor in the 4.4L it's just the regulator in the tank and the pressure is fixed. That's how it looks in this document ==>> http://www.disco3.co.uk/gallery/albu..._Operation.pdf

This is really helpful, Cambo. Thanks! Do you think it would be possible to steam out the original tank properly without damaging any of the internal components (once the fuel pump is removed). The clay is water soluble, but not soluble in fuel (it turns into a gloopy paste which clogs everything up). I am contemplating buying a new fuel pump and putting it in the old tank (fewer ROV and evap. nonsense), but I am concerned about the level of clay dirt in there.

I wouldn't use steam to clean out the tank. Hot/warm water but not steam. The tanks are made of plastic and getting them too hot wouldn't be good for them.

The fuel pressure regulator is meant to give you 65psi, but it's giving you 80psi instead. Why?

It seems rather implausible that high fuel pressure could cause fuel starvation, but you are chasing a weird problem, and here's one thing that is "out of spec" so you can't rule it out until it's "within spec", in my opinion.

I've been told that it's not unheard of for injectors to not open properly if there is too high a pressure pushing against them AND there is a driver / power supply issue to the injectors themselves. I would not expect this to happen with these modern injectors in an AJV8, but you never know...

So the high fuel pressure would not be the cause, but it could be a contributor... maybe...

Have you checked that the injectors are actually opening & cycling as they should? the power/signal to the injectors is good & strong?

You said you've had the ECU "re-mapped to avoid stored data glitches" why? what was done exactly? The ECU files were modified? or just re-flashed with the standard files?

Highly doubt it could be related to the TPS. They either work or they don't (running fine or limp mode, not really anything in between).

There should be a purge solenoid that lets the engine breathe in fuel vapour from the fuel tank. If the solenoid is not working properly, as in an open state for example, it will let in unmetered air and may cause a lean fuel state or at least poor idle and drivability issues.

If you haven't already done so, isolate the solenoid and block off where its hose meets the inlet manifold. For the time being, let the fuel vapours vent naturally ie, into the atmosphere. Reset the engine management and go for another drive.

There is clearly a relationship between ambient temperature and the way your rig operates and the purge solenoid may be to blame as the fuel vapour in the tank increases with outside temperatures. Give it a go and report back.

Originally Posted by Cambo351

I wouldn't use steam to clean out the tank. Hot/warm water but not steam. The tanks are made of plastic and getting them too hot wouldn't be good for them.

Gotchya. Theres a rad cleaning place that I was thinking of taking it too -- they do tanks too. I was concerned about the front fuel sender which I cannot get out.

The fuel pressure regulator is meant to give you 65psi, but it's giving you 80psi instead. Why?

I am not sure -- the other pump on tank 1 read about that too -- it is possible that the gauge is a bit out -- but 15 psi is a fair margin! I shall double check when my friend with the pressure gauge returns from holidays.

Have you checked that the injectors are actually opening & cycling as they should? the power/signal to the injectors is good & strong?

No, I have no tool to check this. I know the injectors were cycling properly at Land Rover -- though when we ran the tests there, the injector delay was only 7ms, even though we she was running to the point of stalling in the shop. My code reader does not look at injector times. The injectors were replaced with used ones, but off a running vehicle. The electrical plugs were checked when we changed the injectors -- but I have no harness or mechanism to check the ECM pulses to the injectors -- I am working on a bit of a shoestring budget as I am a student, and I have already dumped $2500 into her to try and fix her, and I am no better off now than when I started. .

You said you've had the ECU "re-mapped to avoid stored data glitches" why? what was done exactly? The ECU files were modified? or just re-flashed with the standard files?

The ECM was flashed with standard files. I wanted to ensure that there was no logging of improper data due to any spurious data from the flooding. The ECM took the flashing with no issues, which helps me think that the ECM is not at fault (I'd have expected difficulty with the flashing if there were ground issues or something with the ECM).

Highly doubt it could be related to the TPS. They either work or they don't (running fine or limp mode, not really anything in between).

No, I don't either -- but I want to check every fuel related sensor. If I rule out all of these sensors, it has to be fuel supply -- but I've never heard of a resetting fuel supply issue!?

Hmmm....

80psi - 65psi = 15psi which is about 1 atmosphere...

Is the gauge they're using an "absolute" pressure gauge by any chance?

Originally Posted by Cambo351

Hmmm....

80psi - 65psi = 15psi which is about 1 atmosphere...

Is the gauge they're using an "absolute" pressure gauge by any chance?

I'm actually not certain! I can't check until Monday when my friend (the owner of a shop, returns from holiday. What are you thinking?

Originally Posted by banarcus

If you haven't already done so, isolate the solenoid and block off where its hose meets the inlet manifold. For the time being, let the fuel vapours vent naturally ie, into the atmosphere. Reset the engine management and go for another drive.

How do you reset the engine management?

There is clearly a relationship between ambient temperature and the way your rig operates and the purge solenoid may be to blame as the fuel vapour in the tank increases with outside temperatures. Give it a go and report back.

Yes, this had crossed my mind, but I didn't think it would be enough to stall the engine. I've actually ordered the purge valve, and shall inspect the carbon canister while I'm at it. Can you tell me where the engine draws in the evap. air? Maybe I've missed a hose..... The one I disconnected was in the hose before the throttlebody.