Intermittent limp mode

[chigs]

We got 120 ks into our 3000ks road trip when after going over Cunningham gap the 2.7 D4 goes into limp mode and comes to a complete stop. It says transmission fault but when the racq diagnosed it , it came up with throttle position sensor and injector pressure low. The transmission place couldnt work it out so it is now with a landrover specialist but it is still proving very difficult to get a proper diagnosis. The codes say something wrong with high pressure fuel pump but when the pressures are tested the indications are nothing is wrong with the pump. Trying a new ECU next week.

[coopers1969]

Could be low pressure pump in the fuel tank. That is where my issues started from.

[scarry]

Could be low pressure pump in the fuel tank. That is where my issues started from.

My thoughts as well,not common for the ECU to be faulty.

I hope the 'Indie' is experienced with these vehicles, or you may get the run around,unfortunately.

[chigs]

The pump in the tank was tested. I have full confidence in my mechanic as he has specialised in Landrovers for 25 years.

[Discodicky]

Big potential trap here which I only just found out about today. After the fuel enters the fuel filter from the low pressure pump, the fuel goes to the High pressure pump. However the excess fuel which the HPFP doesn't need gets returned from the fuel filter back to the tank. HOWEVER, in the return line to the tank there is a minute Restrictor which is designed to maintain the approx 4-6psi to the HPFP. I have a friend who has on two occasions on a D3 and D4 been chasing an apparent LPFP/HPFP problem and found that this restrictor has come loose from within its "Cage" and thus caused the pressure to drop. Looking at it today, the hole diameter in the restrictor is only approx/roughly .015" (15 thousands of an inch) and the actual restrictor is a very small component which fits within the fuel line to the tank and just before it enters the tank.
Soooo, bear this in mind when chasing potential HPFP/LPFP issues.

[shack]

Big potential trap here which I only just found out about today. After the fuel enters the fuel filter from the low pressure pump, the fuel goes to the High pressure pump. However the excess fuel which the HPFP doesn't need gets returned from the fuel filter back to the tank. HOWEVER, in the return line to the tank there is a minute Restrictor which is designed to maintain the approx 4-6psi to the HPFP. I have a friend who has on two occasions on a D3 and D4 been chasing an apparent LPFP/HPFP problem and found that this restrictor has come loose from within its "Cage" and thus caused the pressure to drop. Looking at it today, the hole diameter in the restrictor is only approx/roughly .015" (15 thousands of an inch) and the actual restrictor is a very small component which fits within the fuel line to the tank and just before it enters the tank.
Soooo, bear this in mind when chasing potential HPFP/LPFP issues.

Are you talking if the relief valve in the tank?

[Discodicky]

Are you talking if the relief valve in the tank?

No no, it is a small "bullet" if you like, only around 8-10 mm long and approx 4-5mm in diameter and with the orifice hole approx .015" hole through its centre. It is within the fuel line and just before the fuel tank.
Definitely not in the tank, however it is necessary to drop the tank to gain access. It is clipped to the external part of the fuel sender unit and is within the fuel return line which is also clipped to the sender unit (for support).
It comes loose within the "cage/housing" (sorry, can't think of a better description) that it sits, which allows fuel to "bypass" it to some extent which causes the pressure to drop.
Thus it gives all the symptoms of a failed LPFP/HPFP!!

If I knew how to successfully post photos etc I'd send it together with a sketch of the fuel system circuit. (am not tech savvy! Groan!)