Fuel Pressure Regulator and Residual Pressure, Checking

Fuel Pressure Regulator and Residual Pressure, Checking

The fuel pressure regulator controls the fuel pressure relative to the Manifold Absolute Pressure.

Special tools, workshop equipment, test and measuring appliances and auxiliary items required







- VAG 1318 Pressure gauge
- 1318/10 Adaptor
- 1318/11 Adaptor
- 1318/16 Adaptor


WARNING!
Fire hazard. Do NOT have anything in the area that can ignite fuel!


Requirements
- Fuel pump delivery rate OK

Test sequence


WARNING!
Fuel system is underpressure! Before opening the system place a cloth around the connection, then release pressure by carefully loosening the connection.







- Disconnect supply line/hose -1- and collect leaking fuel with a cloth.
- Connect VAG 1318 pressure gauge using VAG 1318/10, /11 and /16 adaptors.







- Open pressure gauge cut-off.
- Handle points in direction of flow -arrow-
- Start engine and let idle.
- Measure fuel pressure.
- Specification: approx. 2.5 bar

If specification obtained







- Disconnect fuel pressure regulator vacuum hose -1-
- Fuel pressure must increase to approx. 3.0 bar
- Switch OFF ignition.
- Check for leaks and residual pressure by observing pressure drop on gauge.
- After 10 minutes residual pressure must be 2.0 bar minimum.

If residual pressure drops below 2 bar
- Start engine and let idle.







- Switch ignition off after pressure builds up while simultaneously closing pressure gauge cut-off handle
- Handle perpendicular to direction of flow -arrow-
- Observe pressure drop on gauge.

If pressure does not drop
- Test fuel pump check valve.

If the pressure drops again







- Open pressure tester VAG 1318 shut-off handle.
- Handle in throughflow direction
- Start engine and let idle.
- Switch OFF ignition after pressure has built-up, simultaneously pinch/seal the return line.

If pressure does not drop
- Replace fuel pressure regulator.

If the pressure drops again
- Check line connections, O-rings on fuel rail and fuel injectors for leaks.


WARNING!
Fuel system is underpressure! Before disconnecting the pressure gauge, place a cloth around the connection, then release pressure by carefully loosening the connection.


- Check pressure gauge for leaks.