Generic Scan Tool

Diagnostic Procedures



Fuel Pressure Regulator and Residual Pressure, Checking

• Work on the fuel system must only be performed when engine is cold!

• Fuel system is under pressure! Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.

CAUTION!
Safety precautions => [ Safety Precautions ] Safety Precautions.

Rules for cleanliness => [ Clean Working Conditions ] Clean Working Conditions.

Special Tools and Equipment

• Fuel Inj. Pressure gauge (V.A.G 1318)





• Adapter (V.A.G 1318/26)

Test Conditions

• Fuel pump relay OK.=> [ ] Safety Precautions and => [ ] Safety Precautions

• Fuel Pump (FP) OK.

• Fuel filter OK.

• Battery voltage at least 11 Volts.

• Parking brake engaged.

• Vehicles with automatic transmission: Selector lever in position " P" or "N".

• Electrical consumers switched off (Radiator fan must not run during test).

• A/C system switched off.

• Ignition switched off.

• Safety precautions => [ Safety Precautions ] Safety Precautions.

• Rules for cleanliness => [ Clean Working Conditions ] Clean Working Conditions.

System Pressure, Checking

- Remove engine cover.

- Briefly open fuel filler cap (pressure release).

CAUTION!
• Work on the fuel system must only be performed when engine is cold!

• Fuel system is under pressure! Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.

• Safety precautions => [ Safety Precautions ] Safety Precautions.

• Rules for cleanliness => [ Clean Working Conditions ] Clean Working Conditions.

- Open fuel supply line and absorb exiting fuel using a rag.





- Connect Fuel Inj. Pressure gauge (V.A.G 1318) to fuel supply line.





- Open shut-off tap on pressure gauge. The lever points in direction of flow.

- Start engine and let run at idle.

- Measure fuel pressure.

• Specification: approx. 4.0 bar positive pressure

- Switch ignition off.

- Check for leaks and for residual pressure by observing the pressure loss on the pressure gauge.

• After 10 minutes there must be a residual pressure of at least 2.5 bar

The holding pressure drops below 2.5 bar:

- Start engine and let run at idle.

- Wait until pressure has built up, then Switch ignition off. At the same time, close Fuel Inj. Pressure gauge (V.A.G 1318) cut-off tap (lever at right angle to through-flow direction - arrow -).





- Observe pressure drop on pressure gauge.

If pressure does not drop:

- Check pressure gauge for leaks.

- Check line connections and fuel injectors for proper seal.

If pressure drops again:

- Check pressure regulator in fuel filter:

• Check fuel pressure regulator.

Check Fuel Pressure Regulator

• Fuel pressure regulator is integrated in fuel filter

- Remove carpeting in luggage compartment.

- Unbolt cover for locking flange - arrows -.





- Disconnect fuel return line - 1 - (press release button).





- Position adapter piece - 2 -adapter (V.A.G 1318/26) on fuel return line - 1 -.





- Disconnect adapter piece with hose clamp 3094 at adapter V.A.G. 1318/26.

CAUTION!
Hose Clamps Up To 25 mm Dia. (3094) must not be placed directly on fuel line, otherwise it may be damaged. It may only be disconnected at adapter (V.A.G. 1318/26)!

- Start engine and let run at idle.

- Wait until pressure has built up, then switch ignition off. At the same time, close fuel Inj. Pressure gauge (V.A.G 1318) cut-off tap (lever at right angle to through-flow direction - arrow -.





- Observe pressure drop on pressure gauge.

If pressure drops again, check-valve of fuel pump is leaky.

- Replace fuel pump.

If pressure does not drop:

- Replace fuel filter with integrated fuel pressure regulator.

Assembly is performed in reverse order of removal. Note the following:

• Before disconnecting pressure gauge, release fuel pressure by opening shut-off valve. Hold a container under the connection.

• To avoid damage to the catalytic converter vehicles with engine code BSB may only be started with a cold engine after working on fuel lines or fuel filter.

• Starting the engine can take up to 15 seconds the first time.

- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.