Morris Minor Owners Club

After replacing the fuel tank ( after welding work ) the fuel gauge doesn't register . ( there is fuel in the tank ! ).
How do I test to see if :
(a) gauge is defective ?
(b) if the sender unit is defective ?
(c) wire is broken, somewhere ?

Any assistance would be appreciated . Many thanks
Arfron

Arfon,

Grab a multimeter (you know, measures volts, amps & resistance).

Check that resistance of the fuel sender unit (in the tank) between the contct and the tank (IIRC it uses the fuel tank as an earth contact). Slosh the tank & see if the reading changes (Please use only a 9v battery type resistance meter - I'd hate to read that you used 240v and burnt Monmouth to the ground!).
If that's ok, then check that there is voltage to the sender unit form the regulator on the back of the speedo.
If that's ok, check that the fuel guage reads empty without the regulator supply and moves when there's power (connect the other side to earth.
That should give you the basics, you should also note if there's power where it should be all thriugh the wiring.

Colin

The power supply goes through the gauge and earths at the sender.
Therefore you can check the whole circuit up to the sender by removing the wire from the sender and connecting it to ground - this should give 'full' reading on the petrol gauge. If it doesn't then it's not the tank or the sender causing the problem.
I would guess that your gauge does read full and therefore something on the tank or sender is not making a circuit (as these are the bits that were worked on). Try connecting the body of the sender directly to a good earth to see if that changes anything.

Once you've done these simple checks then use the multimeter to check the parts you suspect as described in Colins post. Otherwise you may end up stripping the dash when the problem is in the boot or vice-versa.

Many thanks for your help Colin + Ray-L'ton. I will check the system ,as suggested . Cheer ! Arfron

Did you refit your original tank or a different one? If the original
have you painted/undersealed everything in sight so that the tank
is no longer in metal to metal contact with the body? This would
prevent the gauge from working. ( The petrol feed pipe could have
a plastic section in it which would prevent it from supplying an earth).

Yup ! It was the original tank + 2 coats of Hammerite + sealed into the boot recess with silicone sealer -- I guess I have insulated the tank?? !! Any ideas for earhting the tank -- I'm not taking it out again !!! I gusee an earth lead from one of the tank screws to earth would do the trick ? Unless anyone has another solution . Be polite !! I haven't had a chance to do the other electrical checks ! Regards Arfron

I haven't had a chance to do the other electrical checks !

I'd do the checks before making any mods - I'm sure we've all done it at least once (fixed the wrong thing only to find it was something else that was the problem)

As Ray said do the simple check 1st it only takes 30 seconds.

by removing the wire from the sender and connecting it to ground - this should give 'full' reading on the petrol gauge

Hi , Fair point Ray . I will do the suggested checks first: with any luck, today ? Regards Arfron

Hello Arfron,
you are quite right, all it would need is a length of (preferably black) wire from the sender securing screw to the body or earth on your wiring loom.

Alec

Good news guys . My fuel gauge is back on - line !! I did the suggested checks , and discovered that the tank was not earthing ,owing to the copious amount of paint/silicone sealer around the tank. The solution was to cleaan out 2 tank screw holes , and put in two slightly larger screws to make a better earth -- BINGO . 'ER in the car' reported a 'twitch of the needle' and I'm back in business. ( I also cleaned the spade connectors on the tank end .)
Many thanks to everyone who helped-- your advice is always helpful and appreciated !! Regards Arfron

Great stuff Arfon, there is nothing like a simple solution to put a put smile on the face

[quote="Arfron"] Good news guys . My fuel gauge is back on - line !! I did the suggested checks , ...

Well done Arfron. Encouraging to read successes.

I spoke too soon when I announced my needle twitching, then working perfectly this week.

Not working today. I shook, wriggled, rocked and rolled [not literally] but no twitch! Not sure what passers by thought. I did all of that while at my allotment. Steamy windows! Cue Tina.

Ho hum. I guess I have to 'do the checks'

Or maybe tomorrow it'll work

Chrissie n HUT

1952 Series MM, 918cc side valve, 4 door saloon, split screen, spoilt monster...