Fuel tank gauge

[Tiger]

Back working on my Ruby Mk2 
Can anyone help with the best way to test the tank unit.
If possible I don’t want to remove the tank.
No access hole in the floor.
I have tested the wire from the unit BUT no electrical path to body earth.
I also have a black wire attached to the unit side.
Regards
            Tim

Thanks in anticipation

[Chris KC]

http://www.austin7.org/Technical%20Artic...20Working/

Any help?

[John Cornforth]

Hi Tiger

The sender body earths via its multiple screws to the tank, which in turn earths to the engine block via the copper petrol pipe. The tank was originally mounted with rubber "dogbone" washers, so may or may not also earth to the body/chassis at its fixings. The black wire on the unit side may be a supplementary earth to the body/chassis that someone has added in the past.

The sender resistance ranges from 2 or 3 ohms minimum to 25 to 30 ohms maximum. Depending on which variant you have, maximum resistance may equate to a full tank or an empty tank. The gauge therefore has to match the sender.

[DaveT]

I had problems with my sender unit on my MK1 Ruby and the easiest solution is to carefully measure the position of the unit in relationship to the back seat floor then using a small drill to cut a hole in what you think is the centre, stick a rod through to confirm your measurements. 

Then using a shortened jig saw blade cut a circle approximately 7" over the unit. once done the access is easy to remove the unit. To complete the job I then cut a thick cover of hard plastic, drilled 6 holes around the parameter and using gasket between them screw the plate onto the floor. 

It's never leaked and it's allowed me to remove the unit on several occasions when problems like a leaking float have occurred. It also allows you to inspect the inside of the tank.

Problems solved

[Tiger]

Thank you very much for such a quick response.
Very helpful.
Tim