Warning! The fuel system is under high pressure. Before disconnecting any of the fuel system components, it is recommended to place rags around the connection. Then relieve the pressure by carefully loosening the connection.
1. Disconnect the fuel line (with a white mark) 1 and seal it (Fig. 4.40).
2. Connect the VAG 1318 pressure gauge using the 1318/10 adapter to the fuel line and, using the 1318/11 and 1318/16 adapters, to the fuel delivery line (Fig. 4.41). Open the pressure gauge valve (the handle should point in the direction of the arrow).
3. Start the engine and let it idle.
4. Measure the fuel pressure. It should be approximately 2.5 bar.
5. Disconnect the fuel pressure regulator vacuum pipe (arrow) (Fig. 4.42). The fuel pressure should increase to approximately 3.0 bar. Switch off the ignition.
6. If the specified value is not reached, check the fuel pump supply.
7. If the set value is reached, check for leaks and the holding pressure by observing the pressure drop on the pressure gauge. After 10 minutes it should be at least 2 bar.
8. If the holding pressure is less than 2 bar: start the engine and let the engine idle.
9. Turn off the ignition after the pressure has increased. After a while, close the pressure gauge valve (the handle should point in the direction of the arrow) (Fig. 4.43).
10. Observe the pressure drop on the pressure gauge.
11. If the pressure does not drop: check the fuel pump bypass valve.
12. If the pressure drops again: open the pressure gauge valve (handle in the direction of the arrow) (Fig. 4.41).
13. Start the engine and let it idle.
14. Turn off the ignition after the pressure has increased. After a while, close the fuel drain line (with blue markings) 2.
15. If the pressure does not drop: replace the fuel pressure regulator.
16. If the pressure drops again: check the fuel line connections, the sealing rings on the high-pressure fuel line and the injectors. Check the pressure gauge for fuel leaks.
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