MG Car Repair: Fuel Pump Versus Fuel Sending Unit, low pressure gauge, fuel sending unit

Question
I just bought a 1970 MGB to restore that had been stored since 2005 and the first step is to get it running again. It is not sending fuel to the carbs, so I started checking with the fuel pump. After trying to start the car with about 1 gallon of fuel in the tank, the gas line to the fuel pump is dry and the rest of the way to the carb as well. I checked the lines to make sure I could push compressed air through it freely to the tank and carb's. Everything seems fine.

My question is, how do I tell if it is the fuel pump or the fuel sending unit? The fuel pump makes the clicking noise, but it had been replaced with some after market fuel pump. Does the clicking noise mean that it is working fine? How would I tell if the fuel sending unit is bad?

Answer
Hi Robert,
The fuel sending unit is an electrical device that tells the fuel gauge how much fuel is in the tank and only one gallon will probably not even register on the gauge and the one gallon probably will not even reach the end of the pick up tube for the fuel pump. The original pump clicking is what they did when trying to pump air instead of gas since you didn't put enough gas in the tank to even find out if it worked or not.

Standard procedure would have been to put at least 5 gallons of gas in the tank and then remove the fuel line from the carburetor and put in into a jar or can and turn the ignition on and you should hear the pump click rapidly until gas starts to go into the can and at that time the clicking should slow down. Then turn off the ignition and put a low pressure gauge on the line and turn on the key again and you should hear the pump click a little and then slow to a stop and then click on occasion and the fuel pressure should be between 1.5 PSI and 3 PSI but not over 3 PSI. Turn the key off and reconnect the line to the carburetor and turn on the key again and listen to the pump which should start clicking slowly for a few seconds and stop and then only click occasionally.
Howard