System Pressure and Holding Pressure, From 07.03, Checking
System Pressure and Holding Pressure, from 07.03, Checking
• Fuel pressure regulator is integrated in fuel filter (under fuel tank) and cannot be replaced individually.
Special tools, testers and auxiliary items required
• Fuel Inj. Pressure Gauge-CIS (VAG1318) with adapters (VAG1318/6) and (VAG1318/7)
Test requirements:
• Fuel Pump (FP) Relay OK; checking. Refer to => [ Fuel Pump Relay and Activation, Checking ] Fuel Pump Relay and Activation, Checking.
• Delivery quantity of transfer Fuel Pump (FP) OK. Refer to => Fuel Delivery and Air Induction Fuel Delivery and Air Induction
• 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).
CAUTION!
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 Fuel Inj. Pressure Gauge-CIS (VAG1318 ) in supply line using adapters (VAG1318/6) and (VAG1318/7).
- 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
• 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 shut-off valve of Fuel Inj. Pressure Gauge CIS (VAG1318) (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:
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 adapter piece (VAG1318/17-1) to return line.
- Pinch off adapter piece using hose clamps up to 25 mm dia (3094).
• hose clamps up to 25 mm dia (3094). 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 shut-off valve of Fuel Inj. Pressure Gauge CIS (VAG1318) (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:
• 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).
- Connect adapter piece (VAG1318/17-1) to return line.
- Pinch off adapter piece using hose clamps up to 25 mm dia (3094).
• Hose clamps up to 25 mm dia (3094). 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 shut-off valve of Fuel Inj. Pressure Gauge CIS (VAG1318) (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:
• 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.