Disco 2 TD5 Low Fuel pressure!!

so in a previous post (here) i discussed where best to fit a fuel pressure sensor to a td5. now after i have it running i m noticed the pressure is way below the ideal 4bar. I have replaced the pressure sender (both quality SAAS senders connected with a T to the temperature temp port) and also using a manual gauge connected to the Fuel feed line. In all cases im getting a readout of around 1.5Bar which drops to 1Bar when i put my foot down. The pump is a genuine Siemens pump, 4-5 years old. I had also replaced the fuel filter housing and everything attached there a bit before and everything seems fine. Car starts fine but i do think its a little down on power. How do i diagnose what the problem might be without loading the parts cannon (if possible?)

SO in summary:

Low fuel pressure measured at the FPR.
FPR has been recently (a month) serviced with a new Bosch diaphragm.
VDO pump had been replaced around 5 years ago
Fuel filter housing replaced around 5 years ago
Fuel filter replaced earlier this year (bosch or mahle, cant remember).

how can i diagnose the issue?

See the pump's drain cos it sems it's running only on LP : https://www.landyzone.co.uk/land-rover/check-td5-fuel-pump-hp.358086/ .... though what's that 114*C reading ???

thanks for the tip! the 114 degree Celsius is from the exhaust manifold.

Checked and its showing 14.4 mV. Could it be caused by corrosion in the fusebox itself maybe?

Check the voltage on the pump's connector across the two pins while it's running, if it drops below 12V check between the live pin and body and if it's the same it's a contact issue somewhere if OK against earth the problem is on the earth path but if it doesnt drop i'd say that the pump is gone even though with that reading it's in the "grey zone"

if the voltag edrops at the pump check on the fuse too against earth

thanks ill do that later as its set up as an overlander with cabinets in the back so i will need to take out a few stuff lol. btw, now the f***er wont start, i suspect it is something to do with disconnecting the Fuel feed line and reconnecting it... but i had done that a couple of weeks ago when i serviced the fpr due to a minor leak i had and did not have any problems purging the system then. to be clear the mV reading is while purging the system,

mad85 said:

now the f***er wont start, i suspect it is something to do with disconnecting the Fuel feed line and reconnecting it.

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That's classic symptom for LP cos untill the system was sealed it ran on residual pressure once released and no HP present they used to not start anymore

sierrafery said:

That's classic symptom for LP cos untill the system was sealed it ran on residual pressure once released and no HP present they used to not start anymore

Click to expand...

So non starter issue kinda made it a priority so i got to work lol. After several attempts it started and seems happy now. Retested the mV at the fusebox and with the engine running it is now 17.4mV, which is still low. Voltage at the fuel pump is 13.5V

I tested the voltage at fuse and noticed that at when end it 14.38V while at the other is 14.36V. is a .02 V drop normal?

Edit: from a little research a 0.02V is acceptable drop, so it seems like the fusebox might not be an issue