System Pressure, Fuel Pressure Regulator and Residual Pressure, Checking
System Pressure, Fuel Pressure Regulator and Residual Pressure, Checking
• Fuel pressure regulator is integrated in fuel filter and cannot be replaced individually.
Special tools, testers and auxiliary items required
• Hose clamps up to 25 mm dia. (3094)
• Fuel Inj. Pressure Gauge-CIS K-Jetronic (V.A.G 1318) with adapters (V.A.G 1318/11), (V.A.G 1318/17) and (V.A.G 1318/23)
Test Conditions
• Fuel Pump (FP) Relay OK.
• Fuel filter OK.
• Battery voltage at least 12.5 V.
Test Sequence
Measuring fuel pressure:
- Pull off cover over fuse holder in left instrument panel and pull out Fuse 27 (on fuse panel C) SC27.
Fuel system is under pressure! Before opening system, place clean rags around the connection. Then release pressure by carefully loosening the connection.
- Disconnect fuel supply line - 2 - at right rear in engine compartment, to do so pull up release button.
• Ignore - 1 -.
- Disconnect fuel supply line - arrow - on fuel rail line.
- Install a fuel-resistant assisting hose on fuel rail line.
• Use hose clamps - arrows - to secure assisting hose.
- Connect Fuel Inj. Pressure Gauge-CIS K-Jetronic (V.A.G 1318) with adapters (V.A.G 1318/11), (V.A.G 1318/17) and (V.A.G 1318/23).
- Open shut-off valve of pressure gauge set.
• The lever points in the direction of flow.
- Start engine and let run at idle.
- Measure fuel pressure.
• Specified value: Approximately 4.0 bar positive pressure
- Switch off ignition.
If specification is not obtained:
Checking seal and residual pressure:
- Check for leaks and for residual pressure by observing pressure loss on the pressure gauge.
• After 10 minutes there must be a residual pressure of at least 3.0 bar.
If residual pressure drops below 3.0 bar:
- Start engine and let run at idle.
- Wait until pressure has built-up, and then switch off ignition. Simultaneously close shut-off valve of pressure gauge K-Jetronic (V.A.G 1318).
• Lever stands perpendicular to direction of flow - arrow -.
- Observe pressure drop on pressure gauge.
If pressure drops again:
- Check line connections and O-rings on the fuel rail and fuel injectors for leaks.
- Check pressure gauge for leaks.
If pressure does not drop:
- Open shut-off valve of pressure gauge (lever in direction of flow).
- Remove rear seat bench
- Unclip catches - arrows - of right connector flange cover.
- Disconnect fuel return line - arrow - by pressing release button.
- Connect adapter piece (1318/17-1) to fuel return line.
- Clamp off adapter piece using a 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.
- Cover return line connection with a cloth.
- Start engine and let run briefly at idle.
- Wait until pressure has built-up, and then switch off ignition.
- Observe pressure drop on pressure gauge.
If pressure does not drop now, check-valve of fuel pump is malfunctioning.
- Replace fuel pump.
If pressure drops again:
- Replace fuel filter with integrated fuel pressure regulator.
• Before disconnecting pressure gauge, release pressure by opening shut-off valve. Hold a container in front of connection for this.
- Assembly is in reverse order of disassembly, noting the following:
- Insert Fuse 27 (on fuse panel C) SC27 again in fuel holder in left instrument panel.
- Install rear seat bench