The Common Rail system uses special injectors with hydraulic boost and an electric start element (solenoid valve) to ensure that the correct amount of fuel is supplied to the combustion chamber.
To ensure the correct amount of fuel injected, the injector must open very quickly, which requires high voltage from the ECU. After the spray needle is fully opened, the current supplied to the solenoid valve is reduced to a value sufficient to hold the solenoid valve in the open position. The amount of injected fuel is determined by the opening period of the nozzle and the pressure in the system. After the voltage supply to the solenoid valve is cut off, the atomizer needle goes down and hermetically shuts off the high pressure fuel supply to the combustion chamber.
Function test
1. Using the clamp meter on the engine tester, check the operation of the fuel injectors. Clamp meters must meet the following requirements:
- measurement range over 25 A;
- frequency range over 100 kHz.
2. Connect the connector to the injector. Place a clamp meter around the injector head, run the engine at idle, and measure the current drawn by the injector and compare the current curve with the curve shown in the figure.
- Current consumption phase value (maximum 12 A) depends on the engine speed.
- The first section of the curve shows the pre-injection of fuel.
3. Check the injector for fuel injection. Disconnect the connector from the injector and connect to an additional injector.
- If the operation of the engine has not changed, the injector being tested does not inject fuel.
- If the operation of the engine has changed, then the injector being checked is working and is injecting fuel.
- This test does not allow you to set the amount of fuel injected by the injector.
- Replace all fuel injectors if necessary.
4. With the ignition off, measure the supply voltage on pins 33 (cylinder #1), 36 and 39 (cylinder #3), 40 (cylinder #2) and 37 ECM. Voltage: 0 V.
5. If the voltage does not match the required, check the condition of the wiring. If the wiring is good, replace the ECM.
Resistance measurement
1. Disconnect the electrical connector from the injector.
2. Measure the resistance between the connector pins. Resistance: 0.3-0.6 ohm at 20°C.
3. Connect the electrical connector to the injector.