Water in fuel filter warning lamp

Hi,

Apologies if this is a simple query - have only just got a 2001 TD5 and have noticed that the water in fuel filter occasionally flashes on. Usually only for a second or two and often when I’m going round a corner. Do you think anything to worry about?

Ben

Drain it, the sensor is telling you there is water present in the fuel filter.

That sensor is too sensitive and can give erratic warnings when it gets old hence LR gave up fitting them on late facelifts, As long as you service your vehicle with care and change filters at decent periods that sensor is useless. I binned mine when it failed and i connected the warning lamp to a coolant level sensor so i know that when i see it the coolant is low

GaelicGinge said:

Hi,

Apologies if this is a simple query - have only just got a 2001 TD5 and have noticed that the water in fuel filter occasionally flashes on. Usually only for a second or two and often when I’m going round a corner. Do you think anything to worry about?

Ben

Click to expand...

It came up for me a few times last summer - fuel tank had been running low for a while and we had a humid spell. I figured with the humidity and a low level tank there might have been a bit of moisture in the tank. Anyway, filled the tank to the brim with diesel, screwed off the sensor and put it back a couple of times and all was fine after that. Only other time it came on was when I was driving for a while in a torrential downpour - where it's positioned behind the rear wheel the sensor gets a bit wet and dirty and the connecting wires are stretched (bent) to the limit when the plug is inserted into the sensor. Not sure if the sensor serves much purpose, and I can see how it could be tempremental! [Like the idea of re-purposing the wire/input for a coolant sensor - sierrafery]

GaelicGinge said:

Hi,

Apologies if this is a simple query - have only just got a 2001 TD5 and have noticed that the water in fuel filter occasionally flashes on. Usually only for a second or two and often when I’m going round a corner. Do you think anything to worry about?

Ben

Click to expand...

Diesel (hydrocarbon) is non-conductive whilst water is conductive. Water is denser than diesel and sinks to the bottom - hence water should technically build-up at the low point: the sensor below the fuel filter. The water will allow the sensor circuit to become complete and the warning light comes on. That's the theory I understand. [I assume any water that ultimately gets through might potentially damage the injectors (as steam)?]

The sensor reacts to the water which was already sedimented and got to the bottom of filter so that water will not get into the injectors unless you don't change the filter at time and it gets full of water(that's why i mentioned decent servicing) and as LR gave up on it i think it's not so important. So change the fuel filter at least once a year and it will be OK.

The sensor has an electronic circuit within to controll the current at the limit and they had something in mind as if the warning stays illuminated for a longer time(i dont know exacly how long) the current will melt the fuel pump's fuse cos it's on the same ciruit(maybe LR thought to protect the injectors this way)... though i've seen a case when a friend ended up with engine not running in deep water especially due to the way the circuit of this sensor was made cos water shorted the circuit between pins 2(earth) and 3(live from F10) in the plug not through the sensor's drop down circuit.
I cut the W/P wire and isolated it well also i cut the OG wire at C0378/0392 - 11 which goes to the warning lamp and connected the coolant level sensor there(an earth input is needed to illuminate the warning), here are the schemes to make it clear:

Most diesels I see at work have water in fuel sensors.
Not sure if D3 has it, know D4 does.

Lots of moden trucks have water in fuel sensors, and when they see water they open the valve and allow thw water out into a charcoal canister, until that overflows onto the road!

And on how many of those modern trucks the water sensors would blow the fuel pump's fuse in certain conditions? I binned mine knowing exactly it's futility, which seems that was realised by LR too at the end

sierrafery said:

And on how many of those modern trucks the water sensors would blow the fuel pump's fuse in certain conditions? I binned mine knowing exactly it's futility, which seems that was realised by LR too at the end

Click to expand...

Pumps mechanical, electric would not go the distance.