2. Disconnect the fuel shut-off solenoid valve (immobilizer) connector.
3. Disconnect the high pressure fuel pipes and plug all connections.
Fig. 4.12. Location of the connector (arrow) of the injector needle lift sensor
4. Disconnect the connector from the injector needle lift sensor (Fig. 4.12).
5. Remove the fuel return hoses and plug all connections.
6. Using special tool MB996041, unscrew the injectors.
7. Remove the heat shield.
8. Cover the injector holes with a clean rag and after turning the crankshaft with the starter, check for foreign particles on it.
Caution: When turning the crankshaft with the starter, stay away from the injector holes.
Attention! If coolant, oil, fuel, etc. get into the cylinder during compression measurement (as a result of cracks), these substances will heat up and splash out of the hole under pressure, which is very dangerous.
9. Install the heat shield and seal ring onto the cylinder head.
10. Install and secure the compression tester to measure compression in diesel engines.
11. While turning the engine crankshaft with the starter, measure the compression in each cylinder, which should be at least 2000 kPa.
12. After measuring the compression in all cylinders, check that the compression difference between the cylinders is no more than 400 kPa.
13. If the compression in any cylinder exceeds the maximum permissible value or the difference in compression between cylinders exceeds the maximum permissible value, then pour some engine oil into the injector hole of that cylinder and repeat the measurements.
14. If the compression has increased after adding oil, the cause of the malfunction is wear or damage to the piston ring and/or cylinder bore.
15. If the compression does not increase after adding oil, then either the valve seat is burnt out or damaged, or there is a gas (pressure) leak through the cylinder head gasket.
16. Remove the compression gauge.
Fig. 4.13. Position of the thermal pad before installing the injector: A – cylinder head side; 1 – thermal pad flange
17. Install a new thermal gasket into the cylinder head with the flange towards the swirl chamber (Fig. 4.13).
18. Using a special tool, tighten the injectors to a torque of 70 Nm.
19. Reinstall the fuel return hoses.
20. Connect the connector to the injector needle lift sensor.
21. Connect the high pressure fuel pipes.
22. Connect the fuel shut-off solenoid valve (immobilizer) connector.
23. If the check engine light is flashing, clear the diagnostic trouble codes using the MUT-II.