Trouble shooting gas gauge...any hints?

[Healey_Z]

My gauge moves some, bounces a lot, reads full when full and never reads below half full, even when empty.

Any trouble shooting hints; what to check and in what order?

p.s. how many gallons does the BJ7 tank hold?

thx,
Ken

 

[AUSMHLY]

Hi Ken,
It's natural for the needle to bounce around, because of the tank not being baffeled enough.
Check the fuel sending unit, in regards to only reading half when it should read empty. The dash gauge may be off too, but I'd look into the sending unit first. As always, check the ground wires.
The tank holds 14 us gallons.

 

[glemon]

The less sophisticated among us have been known to adjust the guage reading by bending the wire to to float and trial and error.

There is also some good information on fuel guage adjustment on the MGA Guru site. Go here https://mgaguru.com/mgtech/electric/electr_1.htm and scroll down.

 

[gra]

If you know the gauge worked properly in the past this comment is not applicable.

When I first acquired my BJ8, the gauge read as yours does from full to 1/2 full at empty. After trying many things and sending gauge to Nosinger (sp) I learned the gauge was not the right part number for the car and would not read accurately using the correct sending unit. I acquired a proper gauge which fixed the problem. George

 

[Johnny]

Hi Ken, remove the sending unit on top of the gas tank. Mine just needed to be cleaned up, as the wipers on the sides weren't making contact. Also check the small wire that protrudes away from the unit towards the edge, mine was broke. That small wires is grounded to the tank when the screws are tightened. I also added an additional ground strap from one of the mounting screws to the rear bulkhead.

Another thing to check is whether the float attached to the rod isn't filled with gasoline.

Hope this helps, let us know what you find.

 

[Healey_Z]

Thank you for the replies. The bouncy, inaccurate gauge is two down on the "todo" list, and I will post what I find when I dig into it.

I will start at the sending unit and work my way toward the gauge. Does anyone know the resistance measurements at empty / full. The car has been converted to negative ground.

thx,
Ken

 

[AUSMHLY]

Hi Ken, remove the sending unit on top of the gas tank. Mine just needed to be cleaned up, as the wipers on the sides weren't making contact. Also check the small wire that protrudes away from the unit towards the edge, mine was broke. That small wires is grounded to the tank when the screws are tightened. I also added an additional ground strap from one of the mounting screws to the rear bulkhead.
Another thing to check is whether the float attached to the rod isn't filled with gasoline.
Hope this helps, let us know what you find.

Here's a photo of the inside of the unit, for reference.
My sending unit wire was broken. I soldered it back together. You can see the silver solder at the end. Works fine now.

Good luck,
Roger

 

[BigGreen]

... Does anyone know the resistance measurements at empty / full. ...

Look at the document following the link in Glemon's answer ;-)

Hans

 

[Healey_Z]

Big,

I had read that document. It was for MGA's. Do they use the same gauges and sending units as Healeys?

 

[BigGreen]

I looked for the senders and gauges for BJ8 and MGA at the Moss website
Both senders have the same number and informationsheet
The gauges are different, but the resistance might be the same because of the senders being the same

Hans