Fuel Pressure Regulator and Residual Pressure, Checking
Fuel Pressure Regulator and Residual Pressure, Checking
Special tools, testers and auxiliary items required
• Hose clamps up to 25 mm dia. (3094)
• Pressure gauge for K-Jetronic (V.A.G 1318)
• Adapter (V.A.G 1318/26)
Conditions
• Fuel Pump (FP) Relay OK.
• 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).
• Air conditioning system switched off.
• Ignition switched off.
CAUTION!
Fuel system is under pressure! Before loosening hose connections or opening the test connection (for fuel pressure testing), place rags around the connection area. Then release pressure by carefully loosening the connection.
- Briefly open fuel filler cap (pressure release).
- Remove engine cover.
- Cover threaded connections that hold fuel pressure (fuel supply) with a shop rag.
- Open fuel supply line threaded connection - arrow - and catch escaping fuel using a shop rag.
- Install fuel injection pressure gauge (V.A.G 1318) with appropriate adapters between fuel supply line and fuel rail line.
• The shut-off valve of the fuel injection pressure gauge (V.A.G 1318) must be installed on the fuel supply line side!
- Open shut-off valve of pressure gauge. The lever points in the direction of flow.
- Start engine and run at idle speed.
- 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 run at idle speed.
- Wait until pressure has risen, and then switch ignition off. Simultaneously close shut-off valve of fuel injection pressure gauge (V.A.G 1318) (lever perpendicular to direction of flow - arrow -).
- Observe pressure drop on pressure gauge.
The following malfunctions are possible if the pressure does not drop:
• Check pressure gauge for proper seal.
• Check line connections and fuel injectors for proper seal.
If pressure drops again, the following malfunction is possible:
• Check fuel pressure regulator.
Fuel pressure regulator with fuel system without return flow, checking
- Remove carpeting in luggage compartment.
- Unbolt cover for locking flange - arrows -.
- Disconnect fuel return line - 1 - (press release button).
- Place adapter (V.A.G 1318/26) - 2 - on return line - 1 -.
- Clamp adapter (V.A.G 1318/26) with Hose Clamps up to 25 mm dia. (3094).
• The Hose Clamps up to 25 mm dia. (3094) should not be placed directly on the fuel line - this could cause damage.
- Start engine and run at idle speed.
- Wait until pressure has risen, and then switch ignition off. Simultaneously close shut-off valve of fuel injection pressure gauge (V.A.G 1318) (lever perpendicular to direction of flow - arrow -). If not connected, first connect fuel injection pressure gauge (V.A.G 1318) => [ Fuel Pressure Regulator and Residual Pressure, Checking ] Fuel Pressure Regulator and Residual Pressure, Checking.
- Observe pressure drop on pressure gauge.
If pressure drops again, the following malfunction is possible:
• Check-valve in fuel pump leaks, replace fuel pump.
If pressure does not drop now, the following malfunction is possible:
- Replace fuel filter with integrated fuel pressure regulator.
Assembly is performed in reverse order of removal. Note the following:
- Before removing pressure gauge, relieve fuel pressure through shut-off valve opening. Hold a container under the connection.
• Starting the engine can take up to 15 seconds the first time.
- Check fuel system for leaks.
Fuel system, checking for proper seal
- Start engine and let it run a few minutes at average RPM.
• At the beginning, engine may run roughly due to air in fuel supply system.
- Turn engine off and check fuel system for leaks.
- Check DTC memory and erase, if necessary.
- Perform test drive, fully depressing the accelerator pedal at least once.
CAUTION!
Observe safety precautions that apply to road tests => [ Safety Precautions ] Multiport Fuel Injection
- After road test, check fuel system again for leaks.
- Check DTC memory again and erase, if necessary.