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MG MGA - Fuel sending unit

Shucks, on a test run with my bride, the fuel gauge "flickered" for a while and finally pegged to the right. Once at home, I measured "open circuit" at the terminal and "0" ohms to ground on the housing. Now the question; Can I remove the cover plate without spilling the contents of the tank or do I have to drain the tank to look for a broken wire? Thanks, Tom
Thomas McNamara


Unfortunately the latter, you will need to drain most of the gas from the tank. Read through the background on Barney's web site, .

You may need a small amount of sealant on the threads of the mounting screws. Take care to not let any stray gasket sealant get into the tank, it will plug up a filter.


If the tank was only about half full you could jack up the right side of the car to remove the sender unit (or sender unit cover) without draining the tank. There will be fuel inside of the small rectangular cover on the sender unit.
Barney Gaylord

Hey all, using Barney's advice, I jacked up the right side and removed the wheel and then the sender unit. I could find no broken wires or such. It works when I put it all together? Could it be that there was sealant enough to not allow the mounting screws to ground the unit? Thoughts? Thanks, Tom
Thomas McNamara

I suppose I neglected to recommend that you test some things before removing the sender from the tank.

If the gauge sometimes works and sometimes not, then the fault is possibly in the wire connections, power input and grounding of the gauge, grounding of the fuel tank, and a snap connector near the starter switch connecting front harness to side harness.
Barney Gaylord

Hey all, I tested the entire circuit wiring before removing the unit and all was good. The one thing I failed to test was the ground on the sender housing. The tank is/was definatly grounded. Upon inspection, it appears that combined with the insulating gasket, the mounting screws "could" also be insulated by sealant?

All's well that ends well, it seems to work at the moment. If it fails again, a clip cord will tell the tale. Thanks to all. Tom
Thomas McNamara

I thought I saw some time ago that Moss Motors was supplying nylon washers with sender unit mounting screws, intended to seal under the screw heads to stop fuel leakage. Between base gasket and nylon washers it could electrically isolate the sender unit from the tank, defeating the ground connection. I don't think sealant on the screw threads would kill grounding of the screws.
Barney Gaylord

You are disconnecting the battery before working on this right?
Keith Lowman

This thread was discussed between 13/04/2013 and 19/04/2013

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