Releasing fuel pressure in the low-pressure circuit of gasoline models
Attention: The pressure in the low-pressure circuit of the FSI models can be up to 6 bar!
1. Remove the fuel pump fuse or fuel pump control unit from the relay and fuse box (see chapter 12).
2. Start the engine and let it run until the gasoline remaining in the fuel lines is completely used up (until the engine shuts down).
3. Crank the engine over with the starter for about 5 seconds to make sure the pressure in the fuel rail is completely relieved.
4. Install the fuel pump fuse.
5. Even after relieving fuel pressure, when disconnecting the fuel lines, wrap a cloth around the joint and slowly loosen the joint, allowing the fuel to soak into the cloth.
Releasing fuel pressure in the high-pressure circuit of gasoline models
Attention: The pressure in the high-pressure circuit can be up to 120 bar (on models 1.4 and 3.6l) or 150 bar (on models 1.8 and 2.0 l)!
6. On engines 1.8, 2.0 and 3.6 l, disconnect the valve connector "N276" fuel pressure adjustment (on the injection pump. see Section 10), then start the engine and let it idle for about 10 seconds. The pressure is thus reduced to approximately 6 bar.
7. On 1.4L engines, connect the diagnostic tool VAS5051 (see chapter 5), execute its function "Remove high fuel pressure" ("High Fuel Pressure Relief"), and then turn off the ignition. The pressure is thus reduced to approximately 6 bar.
8. Wrap a cloth around the high pressure circuit connection and slowly loosen the connection, allowing the fuel to soak into the cloth.
9. After finishing work, read the ECM trouble codes and clear them (see chapter 5).
Air removal (pumping) from the fuel supply system of diesel models
10. Bleeding the fuel supply system is necessary after removing the parts located between the fuel tank and the injection pump. The purpose of bleeding is to prevent the injection pump from running dry, which can lead to its breakdown, and to ensure reliable engine starting.
11. When bleeding, the DSG must be set to "R", the fuel tank must be filled and the fuel temperature must be at least 15°C.
12. To bleed, connect the VAS505X diagnostic tool to the vehicle's diagnostic connector, turn on the ignition, select in the self-diagnosis "Engine electronics > 006 - Basic settings > "Test of fuel pump for predelivery". and then successively press "Start". The fuel pump will run for about a minute. Repeat this procedure three times.
13. Start the engine, let it idle for a few minutes and turn it off. Make sure there are no fuel leaks.
14. Clear Trouble Codes and Do a Road Test (see Section 20 of Chapter 1), at which at least once accelerate once with the gas pedal fully depressed. If there is air in the fuel supply system, the engine may switch to emergency operation during a road test. In this case, clear the trouble codes and repeat the road test.
15. After a road test, check again for fuel leaks and erase the trouble codes again.
Pumping out fuel from the tank
Note: The procedure is described on the example of petrol models: for diesel models, the steps are similar.
Note: If the fuel pump is faulty, the fuel can be pumped out with a suitable tool such as the VAS5190.
16. Turn off the ignition and electrical appliances. remove the key from the ignition.
17. Fold back the rear seats and their backs. remove the floor covering underneath.
18. Unhook the lid (4 to resist. illustrations) with block "J538" (1) fuel pump control. On models with an additional heater, additionally disconnect the 2-pin connector of the metering pump "V54", and if the fuel tank is to be removed, remove the rubber seal from the cap and pull out the wiring.
3.18 Cover with fuel pump control unit
19. Disconnect the 5-pin connector (1 per resist. illustrations) and disconnect the black supply line (2), by pressing on its retaining ring.
3.19 Fuel delivery module connector
20. Connect adapters VAG1318/16 and VAG1318/17 to the fuel supply module and lower the end of this "drain hose" into the fuel collection tank (see resist. illustration). Apply voltage to the fuel pump by connecting it to pin #1 (1) positive wire, and to pin No. 5 (5) - negative wire.
3.20 Extracting fuel