Fuel Pressure: Testing and Inspection
Fuel Pressure and Residual Pressure before High Pressure Pump, Checking
Special tools, testers and auxiliary items required
• Pressure gauge K-Jetronic (V.A.G 1318)
• Pressure gauge adapter (V.A.G 1318/10-12)
• Remote Control (V.A.G 1348/3A) with adapter cable (V.A.G 1348/3-3)
• Measuring container, fuel-resistant
Test Conditions
• Battery voltage min. 12.5 Volts.
• Fuel Pump (FP) Control Module (J538) OK; check in "Guided Fault Finding" with Vehicle Diagnosis, Testing and Information System (VAS 5051B).
• Fuel filter OK.
• Fuel tank at least 1/4 filled.
• Ignition switched off.
Fuel Pressure, Checking
- Remove cover of right luggage compartment side trim - arrows -.
- Remove cover - 2 - above battery.
• Ignore - 1 -.
- Remove trim for luggage compartment floor.
- Unbolt cover for left locking flange - arrows -.
- Disconnect electrical harness connector - 2 - at left locking flange.
• Ignore - 1 -.
- Unbolt cover for right locking flange - arrows -.
- Disconnect electrical harness connector - 2 - at right locking flange.
• Ignore - 1 -.
- Connect Remote Control for VAG 1348 (V.A.G 1348/3A) with adapter cable (V.A.G 1348/3-3) and adapter cables from Connector Test Set (V.A.G 1594C) to terminal - 4 - (ground) on left and right delivery unit.
- Route Remote Control (V.A.G 1348/3A) switch forward in engine compartment.
- Connect alligator clip to ground point in engine compartment.
- Connect terminal - 1 - (positive) on left and right delivery unit using a self-made adapter cable to vehicle battery "+". For safety reasons, install a fuse - A - (10 A) in the wiring.
- Remove fuel filler cap from fuel filler tube.
- Remove rear engine cover - 2 - - arrows -.
• Ignore - 1 -.
CAUTION!
The fuel system is pressurized (low pressure). Wear protective eyewear and clothing in order to avoid injuries and contact with skin. Before opening system, place clean rags around the connection. Then release pressure by carefully loosening the connection.
- Disconnect fuel supply line - arrow - at fuel rail.
CAUTION!
Note rules of cleanliness for working on the fuel injection system.
- Connect Fuel Inj. Pressure Gauge-CIS (V.A.G 1318) with Adapter (V.A.G 1318/11) and (V.A.G 1318/12) in fuel line.
- Connect assisting hose - arrow - on pressure gauge and hold it in a container.
- Open pressure gauge shut-off valve. Shut-off valve faces in direction of flow.
- Bleed fuel system by pressing remote control briefly.
- Close pressure gauge shut-off valve. Shut-off valve is perpendicular to direction of flow.
- Press remote control switch until pressure gauge no longer shows pressure increasing.
• Specified value: Approximately 6 bar (5 to 7 bar) positive pressure.
If specification is not obtained:
- Check delivery quantity of Fuel Pumps (FP).
Residual Pressure, Checking
- Check for leaks and residual pressure by observing pressure drop on Fuel Inj. Pressure Gauge-CIS K-Jetronic (V.A.G 1318).
• After 10 minutes there must be a residual pressure of at least 3.75 bar.
If residual pressure drops below 3.75 bar:
• Check connection between Fuel Inj. Pressure Gauge-CIS K-Jetronic (V.A.G 1318) and fuel line for leaks.
• Check pressure gauge for leaks.
• Check fuel lines and their connections for leaks.
• Replace fuel filter with integrated fuel pressure regulator. Then repeat test.
• Replace right Fuel Pump (FP) (G23) if necessary.
Assembly is in reverse order of removal, note the following:
- Switch off ignition.
• Before disconnecting pressure gauge, release pressure by opening shut-off valve. Hold assisting hose in a container.
- Re-install fuel supply line (ensure cleanliness).
Tightening Specifications
