Gas Gauge Broken on '58 Bugeye.??

[BugeyeNJ58]

Problem: Gas gauge always at "E". (Gas is positive ground)

From what I've researched, and read on this site, the gauge doesn't have a voltage stabilizer. I have a green wire in the back of the Bugeye -it wasn't connected. I ran a wire from that and attached it to the post labeled "T" on the gauge. I attached a hot wire to the post labeled "B", and attached a good ground to the center screw that is used for attaching the bracket to the instrument to keep iton the dash.

Turn key on, gauge still at E (all the way). I have another wire going to a good ground, when I touch it to the "T" post, gauge goes all way to F.

Does this indicate that the sending unit from the tank is bad?

thanks....

 

[Sarastro]

I think you have it almost right. There should be a green-black wire to the sending unit and a green wire from the power source. If you connected a hot lead to the B terminal and the solid green to the T, it won't work because you have power-source wires to both terminals. The "T" post means "tank"; i.e., the wire to the sending unit goes there.

There is no voltage stabilizer and no ground is needed.

Are you sure the fuse is OK?

 

[dklawson]

Actually the ground is VERY important on the early gauge system but not the way you normally think of. The CASE of the early fuel gauge MUST have a ground or the gauge will not work correctly. Likewise, the sending unit MUST have a ground or the gauge will not work correctly. Some BMC cars have a ground wire going directly to the sending unit, others have a ground connection for the tank. Some of the Austins pushed the limit by passing the ground on the braided cover of the Petroflex fuel line. When owners replaced that with 'regular' fuel line their fuel gauges typically stopped working.

The wiring is as Steve described. Switched 12V green to the "B" terminal of the gauge, green/black from the "T" terminal on the gauge to the insulated terminal on the sending unit. The gauge case must have a good earth connection (run a new/separate wire if necessary). Finally, make sure the sending unit has a connection to ground and it should work.

More in depth explanations and details can be found on Barney Gaylord's MGA-Guru web site. He has an extensive section covering the early gauge system.

 

[smaceng]

I have heard that some of the new "replacement" gas sending units for the tank are made of plastic, and for that reason, one needs to actually run a wire to the sender. I have a seperate ground wire to the mounting nut on the gas gauge, as my dashboard is not a good ground. BTW, for those that have trouble getting the green flasher light to work, the original cars relied on the ground of the dashboard...I soldered on a ground wire to keep that working a little while longer.
Scott in CA

 

[BugeyeNJ58]

I've got a wire going directly to the sending unit, attached to T. I've got a hot wire going to B, and a ground wire going to the center screw post. Still no good. How can I test the wire from the sending unit?

 

[smaceng]

The sending unit should have a resistance of zero ohns when the tank is empty, and approximately 70 ohms when the tank is full. So take off the T wire from the gauge and measure the resistance to ground.
Scott in CA

 

[nomad]

Ditto on the early guage finicky-ness!! My bugeye guage would'nt work correctly because PO had attached the ground wire somewhere else. Put it under the nut to the screw that clamps the guage into the dash as original and the problem was cured!
Kurt.

 

[Sarastro]

Doug is right about the ground. Dunno where my brain was.

 

[BugeyeNJ58]

Just to double check I'm using the wire from the tank sending unit. When I look up from under the car, I see a green car that is between the top of the tank and the floor. It goes towards the back of the car, then goes into the back of the boot through a hole in the floor.

I'll go measure its resistance now. I'll also check the grounding around the fuel pump.

 

[regularman]

Just to double check I'm using the wire from the tank sending unit. When I look up from under the car, I see a green car that is between the top of the tank and the floor. It goes towards the back of the car, then goes into the back of the boot through a hole in the floor.

I'll go measure its resistance now. I'll also check the grounding around the fuel pump.

That green wire should go to the gauge. There is no ground wire, the sender gets its ground from the tank held by the tank straps. You need to run another wire from somewhere else on the frame to one of the screws holding the sender in place on the tank for a separate and better ground to the sender. That green wire should go through the floor and make its way to the gauge. It should be the same color at the gauge. I don't think any of the spridgets had factory break in this wire.