1. Run the engine to idle.
2. Use a stethoscope to check the operation of each individual valve. Clicks indicate the opening and closing of the injector valves.
3. If a stethoscope is not available, you can carry out the same operation using a screwdriver or a finger.
4. If unusual sounds are detected or no sounds are detected at all, then it is necessary to check the voltage, resistance and tightness of the injectors.
Voltage and resistance test
1. Check the voltage. To do this, disconnect the injector connectors and connect a diode control lamp between both wire contacts. Turn on the starter (assistant). The LED should flash.
2. If the LED does not blink, the fault may be in the wire itself or in the control unit.
3. Turn off the ignition.
4. Attach an ohmmeter to each injector between the contacts and measure the resistance. If any injector has a different resistance, replace it.