MG Car Repair: Fuel gauge, fuel gauge, temp gauge

Question
QUESTION: My fuel gauge does not register full. I replaced the push on connector at the gas tank, the sending unit, and the fuel gauge, and still have the same problem. It goes up between half and 3/4 full and stops. Any ideas?

ANSWER: Hi Bob,
What kind of MG is this?

---------- FOLLOW-UP ----------

QUESTION: My have a 1977 mgb

Answer
Hi Bob,
When you had the sending unit out, did you connect up the wires and try to hand operate the float and watch the fuel gauge operate? This is a test of the system. If you did this and it still did not operate to it's full scale, (Empty to Full)then check the voltage on the fuel gauge and the temp gauge. (light green w/green tracer wire)
The voltage should be about 10 volts. If it is check the grounds on the fuel and temp gauges and the ground on the sending unit to see that they are good grounds. If the voltage is off, replace the instrument voltage stabilizer mounted on the firewall just behind the fuel gauge. (three wires on it, two green and one light green w/green tracer)
Howard