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MGA Fuel gauge question

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C

Coastalman

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My latest project in fixing the little things that are not working on my 1962 MGA is the fuel gauge. The car has been driven about once a year for the last 20 years for no more than 1000 miles until I acquired it a few months ago. The fuel gauge indicator does move sightly in the right direction when the key is turned on. I have put gas in the car so I know there is at least a half a tank. I figured that the float might be stuck after sitting so long in one place. Today I cleaned off the tank sending unit exterior and ran a wire from the post on the sending assy to a ground. My reasoning was that if I grounded the sending unit, the gauge would read full. It did not move past where it has been moving to. What would be my next step in trouble shooting the problem?
Thanks,
Charlie
 
You might check to see if the float has gas in it. I had a similar problem with my TR6.... I knew there was gas in the tank but it read very low. The problem was that the plastic float had fuel in it. I replaced it with a brass float which fixed my problem.
 
I did a test of the gauge by putting a ground lead to the side of the gauge going to the sending unit. My expectation was that the gauge would read full if I grounded the sending unit side. The gauge did not move after the slight forward move that it has been doing when I turn the switch on. Did I have a false expectation that the gauge should read full if grounded?
I'm not going to pull the sending unit until I have another one in hand because I know the gasket will break when I remove it. I'm just checking other parts out before I do that.
 
If the sending unit is stopped in one position for a length of time, the rheostat can get "stuck" in position. Not uncommon with oddly mixed fuel (ethanol) Just had an old Rolls with that issue in Sarasota. Soaked the sending unit in CRC 2-26 for a day, finally got the arm to budge, then worked it GENTLY a bit at a time, got it to move through a complete arc and now it works again.

But the gauge should have gone full travel with the lead grounded. Try the same thing at the gauge itself.
 
That's what I thought! I grounded the wire to the sending unit and, when that produced no result, I grounded the gauge on the down leg side. No movement on the gauge. Someone suggested putting a resistor in line when grounding, but my thoughts, just like you mentioned, was a straight ground would show maximum reading on the gauge. I am ordering a replacement sending unit and try that, but, right now, I don't feel like that is the problem. Most of my knowledgeable friends think it is. A step at a time.
Thanks,
Charlie
 
Resistors are useless. Is it a Lucas or Jaeger? Look to Joe Curto or Nisonger for a gauge replacement.
 
DrEntropy said:
Resistors are useless. Is it a Lucas or Jaeger? Look to Joe Curto or Nisonger for a gauge replacement.
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runs and hides - back to the conversation.
 
:lol:
 
A bit late here, but in case you haven't figured it out yet, then MGA uses a magnetic fuel gauge, and it works backward from what you might expect. Grounding the sender wire drives the gauge to "E". Increasing resistance moves it higher. About 70-ohms resistance takes it up to "F". Higher resistance drives the needle past the "F" mark. Disconnection the sender wire will slam the needle hard against the "F" peg. For full description of the magnetic fuel gauge see here:
Function: > Fuel gauge function - a <
Calibration: > Fuel gauge calibration - a <
Wiring: > MGA fused ignition circuit, petrol gauge <
Trouble shooting: > MGA petrol gauge troubleshooting <
Sender unit: > Fuel sender unit - general notes <
 
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