Fuel gauge temperamental...

virtualme123 · Mar 30, 2011

Fuel gauge tempermental ...
Have a P38 2.5 DSE and ran out of fuel the other day after the gauge decided not to tell me I was low. Now since then I haven't been trusting it and also wanted to change the fuel filter last night because after running low assumed that changing it was a sensible idea.

Although I didn't have time to take the fuel filter off because it was so tight I accidentally left the heater and MAP plugs out, then drove to work this morning! I did find it a little sluggish but otherwise was surprised it worked, but also surprised that the fuel gauge came to life. Does anyone know why the fuel gauge would suddenly work and whether it could be related to the plugs being left out? Haven't tried the gauge with the plugs back in yet but be interested to see if it works again now.

Tried posting this on another landrover forum but had no luck, hoping someone here can help.

Thanks

wammers · Mar 30, 2011

virtualme123 said:
Fuel gauge tempermental ...
Have a P38 2.5 DSE and ran out of fuel the other day after the gauge decided not to tell me I was low. Now since then I haven't been trusting it and also wanted to change the fuel filter last night because after running low assumed that changing it was a sensible idea.

Although I didn't have time to take the fuel filter off because it was so tight I accidentally left the heater and MAP plugs out, then drove to work this morning! I did find it a little sluggish but otherwise was surprised it worked, but also surprised that the fuel gauge came to life. Does anyone know why the fuel gauge would suddenly work and whether it could be related to the plugs being left out? Haven't tried the gauge with the plugs back in yet but be interested to see if it works again now.

Tried posting this on another landrover forum but had no luck, hoping someone here can help.

Thanks

Cannot think of any reason why fuel gauge should be inflenced by that. Mine also has a mind of it's own around the half full mark. Goes from one mark over half to one mark less than half in about four miles. That's because the tight git who had it before me only ever filled it to half full. It's worn out around there. New pump i am afraid if you want to change sender. Unlike petrol they are not available seperatly.

virtualme123 · Mar 30, 2011

Well it does seem strange because I've recently popped both the plugs back into the fuel filter housing and now fuel gauge is conpletely screwed again. Wondering if the MAP sensor is the culprit but can't think how, doesn't seem like a short circuit, more like logic is mixed up. Is the fuel gauge sensor just driven by the sender? Would the fuel pressure have been different if MAP sensor was disconnected, fuel maybe behaving differently? Clutching at straws a bit

Thanks

wammers · Mar 31, 2011

virtualme123 said:
Well it does seem strange because I've recently popped both the plugs back into the fuel filter housing and now fuel gauge is conpletely screwed again. Wondering if the MAP sensor is the culprit but can't think how, doesn't seem like a short circuit, more like logic is mixed up. Is the fuel gauge sensor just driven by the sender? Would the fuel pressure have been different if MAP sensor was disconnected, fuel maybe behaving differently? Clutching at straws a bit

Thanks

Without trawling through the wiring diagrams can't answer that. But obviously sender unit signal is used by fuel computer, to give you a range from quantity of fuel in tank, compared to fuel being used by engine. The MPG is measured by comparing fuel used to miles covered. All this is put together by ECU so i suppose thinking about it it could be an ECU problem. But you would have to study diagrams to find out exactly what is connect to what and where.

Datatek · Mar 31, 2011

I never trust fuel guages, I always reset the trip when I fill up, I know how far it will go before I need to refuel unless of course something goes wrong like leak off pipes failing, but it's a good back up to the fuel guage.

virtualme123 · Mar 31, 2011

Well thanks for your thoughts, I am used to fuel gauges not working but thought the P38 one might be more reliable. Suppose it could be the sender unit playing up and not having the MAP plug in might have been a coincidence. I'll look into the ECU's but no holding out much hope understanding the wiring ...

If I find a solution I'll let you know.

Cheers

Derek Ward · Mar 31, 2011

The fuel gauge sender is a normal resistance type and feeds into the BeCM, It then converts this analogue signal to a digital one to drive the gauge itself. Can't for the life of me figure out how the MAF could affect this as that feeds into the ECU, not the BeCM. However, I'm sure much stranger things have happened on a P38

virtualme123 · Apr 6, 2011

Think this might be the sender not working correctly as there might be a difference when I have the fuel over a certain level, problem is diesel is not so cheap so when I have a windfall I might try half a tank to see if that proves the theory

Cheers

blackburnbertie · Feb 25, 2017

Mine is a bit dicky too but it under reads. I can put 50 notes in and it'll go to half way then after about 10 mins it pops up to three quarters. It's not the sender as I've had a new in tank pump and float put in. Been told it may be a matter of voltage.

Fuel gauge temperamental...

virtualme123

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wammers

No longer with us, RIP

virtualme123

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wammers

No longer with us, RIP

Datatek

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Derek Ward

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