System Pressure and Holding Pressure, Checking

System Pressure And Holding Pressure (vehicles As Of 07.03), Checking

NOTE: Fuel pressure regulator is integrated in fuel filter (under fuel tank) and cannot be replaced individually.

Recommended special tools and equipment

- Fuel Inj. Pressure Gauge-CIS V.A.G 1318 with adapters V.A.G 1318/6 and V.A.G 1318/7

Test requirements:
- Fuel Pump (FP) Relay OK; checking.
- Delivery quantity of transfer Fuel Pump (FP) OK
- Fuel filter OK
- Vehicles with automatic transmission: Selector lever in position "P" or "N".
- Battery voltage at least 12.7 V

Test sequence

- Remove rear engine cover (arrows).

Checking system pressure
- Open fuel filler cap briefly (pressure release).

WARNING: Fuel system is under pressure! Before opening system, place rags around the connection. Then release pressure by carefully loosening connection.

- Unscrew fuel hose from connection on fuel rail pipe. To do so, counterhold using an open-end wrench at each hex head -1- and -3- and unscrew union nut -2-.

- Connect V.A.G 1318 Fuel Inj. Pressure Gauge-CIS in supply line using adapters 1318/6 and 1318/7.

- Open shut-off valve of pressure gauge. The lever points in the direction of flow.
- Start engine and let run at idle.
- Measure fuel pressure.
- Specified value: 3.8 to 4.2 bar
- Switch ignition off.

Checking holding pressure
- Check for proper seal and residual pressure by observing pressure drop on pressure gauge.
- Specified value with a cold engine: approx. 2.2 bar
- Specified value with the engine at operating temperature: approx. 3.0 bar

NOTE: Pressure increase for an engine at operating temperature due to fuel expansion is normal.

If holding pressure sinks below 2.2 / 3.0 bar positive pressure:
- Start engine and let run at idle.

- Wait until pressure has built up, and then switch off ignition. Simultaneously close shutoff valve of V.A.G 1318 Fuel Inj. Pressure Gauge-CIS (lever perpendicular to direction of flow -arrow-).
- Observe pressure drop on pressure gauge.

If pressure drops again:
- Check pressure gauge for proper seal.
- Check line connections and fuel injectors for proper seal.

If pressure does not drop now:
- Check pressure regulator in fuel filter:
- Vehicles with Front Wheel Drive (FWD)
- Vehicles with All Wheel Drive (AWD)

Checking fuel pressure regulator - vehicles with Front Wheel Drive (FWD):

Sedan:
- Remove luggage compartment lining.
- Push forward the right backrest of rear seat, if necessary.

Station wagon:
- Remove left 1/3 backrest.
- Remove left side trim in luggage compartment and dirt tray.

All:

- Remove cover for connector flange (arrows).

- Disconnect fuel return line (arrow) (press release button).

- Connect V.A.G 1318/17-1 adapter piece to return line.
- Pinch off adapter piece using 3094 hose clamps up to 25 mm dia.

NOTE: 3094 hose clamps up to 25 mm dia. must not be placed directly on fuel line, otherwise it may be damaged.

- Start engine and let run at idle.

- Wait until pressure has built-up, and then switch off ignition. Simultaneously close shutoff valve of V.A.G 1318 Fuel Inj. Pressure Gauge-CIS (lever perpendicular to direction of flow -arrow-).
- Observe pressure drop on pressure gauge.

If pressure drops again, check-valve of fuel pump is leaky.
- Replace Fuel Pump (FP).

If pressure does not drop now:
- Replace fuel filter with integrated fuel pressure regulator.

Assembly is performed in the reverse order of removal, noting the following:

NOTE: Before disconnecting pressure gauge, release pressure by opening shut-off valve. Hold a container in front of connection for this.

- Secure fuel hose to connection on fuel rail pipe. To do so, counterhold using an open end wrench at each hex head -1- and -3- and tighten union nut -2- to 22 Nm.

Checking fuel pressure regulator - vehicles with All Wheel Drive (AWD):
- Remove rear seat bench.

- Remove cover for left connector flange (arrows).

- Disconnect fuel return line (arrow) from connector flange (left side of vehicle).

- Secure fuel hose to connection on fuel rail pipe. To do so, counterhold using an open end wrench at each hex head -1- and -3- and tighten union nut -2- to 22 Nm.