Which test validates that an injector is functioning properly during cranking?

The noid light flash test is designed specifically to verify that the fuel injector is receiving the proper electrical signal from the engine control unit (ECU) during cranking. This test involves connecting a noid light to the electrical connector of the injector. If the fuel injector is functioning correctly, the noid light will flash in response to the signals sent by the ECU, indicating that the injector is opening and closing as it should. This is critical for ensuring that the correct amount of fuel is being delivered to the engine during the cranking phase, which is necessary for starting.

The other tests provided serve different purposes. For instance, the spark plug test checks for spark generation in the ignition system rather than fuel injection, while the pressure gauge test is used to measure fuel pressure in the fuel system as a whole. Lastly, the fuel pressure regulator test evaluates the operation of the regulator itself and its ability to maintain the correct fuel pressure but does not specifically confirm the operational status of individual fuel injectors during cranking. Therefore, the noid light flash test is the correct method to confirm the proper function of an injector during cranking.