Fuel gauge randomness

[Piggy]

After doing the gearbox on the Racetractor ...

I have fuel gauge randomness.

Which seems totally unrelated. 

Basically, fuel gauge reads almost full when you turn ignition on. After some driving it gradually, in increments, goes down to what it it actually is. 

Turn ignition off, it doesn't drop down to its stop. 

Physically you can't push it back, it just springs back to max.

Any ideas?!

[TommiePuglet]

Could the clock have given up I have just stripped a clock from a HDI and no matter what if i pull the needle up to half the clock slowly drops down...

[Piggy]

It's working...sort of.

Today it has showed empty with light on just once... Now back to 3/4 tank lol

[welshpug]

I would imagine its just a coincidence it happened when you had the box out.

[TommiePuglet]

It's working...sort of.

Today it has showed empty with light on just once... Now back to 3/4 tank lol

Simple way to find out remove clocks from Lemon and put them in race tractor and see if it imitates if it doesnt id say its clocks.

[Piggy]

I would imagine its just a coincidence it happened when you had the box out.

Serious coincidence.... 


May have to do clocks change which is a total pita

Just broken down as run out of fuel. Went by mileage but obviously been hooning too much

[cully]

short the sender out in the tank plug turn ign on should read 100%
open circuit turn on ign 0%

[Piggy]

short the sender out in the tank plug turn ign on should read 100%
open circuit turn on ign 0%

Yeah was going to try this today.

Odd thing happening is it's been reading 100% with ignition off!

[Piggy]

Unplugging the sender/shorting the plug...

Makes no difference what soever.

[cully]

clocks supply the voltage to the sender and read the return from the sender to give you the fuel level
probably clocks issue
or could be loom if its been tampered or damaged

[Mighty306]

If it's the clock Piggy would a quick temporary fix be to wire a simple voltage display like this directly across the sender unit & stick it somewhere on the dash?

https://m.ebay.co.uk/itm/WATERPROOF-DC-3...mwBanner=1

I assume sender reads gives 12v at full tank n 0v at empty or vice versa?

[Mighty306]

Mmm, a little more research on rheostats reveals I've most likely simplified things but am sure Cully will shine some light on it

[cully]

clocks may send 5v to the variable resistor in the tank im not sure
with in theory you could use any electric oil pressure or temp gauge and wire it into the tank resistor

[Piggy]

There was 10volts at the plug pin for the fuel level sender.
12 for the pump.

[Piggy]

Clocks do appear to have failed. Most random that it happened when I did the gearbox change.