This fuel shutoff valve is a part of the injection pump that functions as the shutoff of fuel and engine. It is operated by a current from the battery through the ignition switch.
When the ignition switch is on and current goes to this shutter it opens and fuel will flow to the injection pump that supplies the nozzles spraying fuel to the combustion chambers. When the ignition switch is off this valve will close and no fuel will flow to the injection pump.
How do you know this?
I would like to share with you our experience in the Toyota L engine. We have just overhauled it, the radiator was overhauled too, and the injection pump calibrated. Everything should have been fine as expected. The engine was cranked and it started smoothly, the engine noise is just right, the thick white smoke is gone and is about to be on a road test.
But as the engine is warmed up it suddenly stalled, no matter how you crank it in order to start it didn’t. Because it’s newly overhauled maybe the fuel has not yet fully saturated the injection pump and air maybe inside. The remedy is to loosen the nozzles so that air may be blown out.
This process if the air had been totally out from the injection pump fuel should follow to come out of the nozzles. If there are no bubbles coming out it’s time to tighten it. Loosening the nozzles to test if there is fuel in it should be done one after the other.
However, this time there was no air coming out and there was no fuel too. So how would the engine start if there is no fuel supplied by the nozzles? It will not. It’s good the fuel hose is transparent and obviously, the fuel is still sufficiently available from the tank.
The next step is to check if there is a current going to the fuel shutoff valve. So we checked it and there was no current. Upon examination, it was the wiring connected to the shutoff valve that has been cut off inside, however, it was not obvious until we stretched it out and it was only connected temporarily through the insulation of the wiring.
When the connection was restored the engine was cranked and it started until it was tested on the road and until this time of writing the engine did not stall.