If pressure drops below 1.2 in. mercury:
- Check/replace fuel filler cap.
- Pressurize system to 1.3 in. mercury.
If pressure still drops below 1.2 in. mercury:
- Remove hose from the top of the gravity vent valve and plug hose.
- Pressurize system to 1.3 in. of mercury.
If pressure still drops below 1.2 in. mercury:
- The leak is between the gravity vent and charcoal filter.
If pressure does not drop below 1.2 in. mercury:
- Check hoses/connections at fuel separator, fuel tank and fuel filter with soapy water.
- After tests are completed, close both valves on tester.
The leak which you have repaired may have allowed contaminants to enter the fuel system, therefore:
Inspect the inside of the fuel tank for fuel contamination.
- Remove the fuel gauge sending unit.
- Carefully inspect the interior of the fuel tank with a flashlight.
If the fuel is contaminated but the interior of the tank is not corroded:
- Remove the fuel tank including the fuel pump supply hose.
- Check the inside of the fuel filter neck, replace if corroded.
- Remove and clean the in-tank fuel strainer. (Replace in-line fuel pump filter on Audi 4000).
- Thoroughly flush the tank and fuel pump supply hose.
- Reinstall the in-tank fuel strainer, make sure that it is completely seated.
- Reinstall the fuel tank.
- Fill tank with clean fuel.
- Run engine for about 15 seconds, then replace fuel filter.
If the fuel is contaminated and the interior of the tank is corroded:
- Replace the fuel tank.
- Check the inside of the fuel filter neck, replace if corroded.
- Inspect and flush all lines between the fuel tank and fuel distributor.
- Replace the fuel filter.
- Disconnect the injector lines at the fuel distributor. Replace the fuel distributor if corrosion is found inside.
- Check for corrosion at the fuel inlet to the control pressure regulator.
- Replace the control pressure regulator if corrosion is found inside.
- Disconnect the injector lines at the fuel injectors. Replace injectors which have corrosion inside.
Reconnect all lines and check for leaks – then return to step 2 of basic checks on page 12.
Add appropriate repair time from SRT manual