I'm not sure if he factory-installed electric fuel pump is working correctly in my 73. I removed it and if I apply 12v, it pumps fine, I'm just not sure if the relay is working correctly, and haven't had the car running to find out if it kicks on when it should.

So when exactly is the electric fuel pump supposed to come on?

And....

If the electric pump is not working properly, does it restrict the flow of the gas from the mechanical pump, or will the mech. pump still work fine?

I believe it gets it "turn on Signal" from the tach wire, if I remember correctly. When the tach gets sufficiant signal (car is running) the relay for the pump turns on.

As for the Mech. fuel pump. It works on a diaphram valve (kinda like the one way valve on a gas mask. so fuel can be pushed past the diaphram if the mech pump fails and the Electric pumps is working properly. The electric pump should allow fuel to pass if it's being sucked to the front by way of mechanical pump.

not 100% sure but it sounds right to me. Anyone else wanna chime in?

Dave