There is no "shutoff" internal to the pump. ECU just stops providing current to the pump to shut it off. If you do not have a scope, try placing an amp clamp on one of the injection pumps solenoid wires. Do you read amperage while in the crank no start mode? Below is a screenshot from an injection pump that received its orders from the ECU, but did not start. You can see what amperage to expect when cranking. From this test, hopefully you can determine if it is electrical or mechanical.