How does the fuel shut off solenoid work?

[Sparky95]

I know that when the solenoid loses electrical power, it cuts the fuel off. But does it allow the fuel to bypass the plungers in the IP? Or does shut off the fuel before the plungers? Or what?

Basically, I unplugged the solenoid today while bleeding the filter housing. After I filled the filter up cranking the engine over, I plugged it back in. The truck fired up in about 10 seconds without cracking injector lines. Then I got to wondering about how bad that was on my almost brand new pump, and discovered I can tell you what it does, but not necessarily how it does it.

 

[Black dawg]

Losing power to the fss moves linkage in the pump and forces metering valve closed. no fuel to plungers.

I always unhook fss after filter change and crank (with power to advance solenoid) so that air goes easily out the return of the pump and not into the fuel charging side of the pump.