Fuel Pump, Checking

Fuel Pump, Checking

Special tools, testers and auxiliary items required

• Pressure gauge (VAS 6550)

• Remote control connection (V.A.G 1348/3A)

• Test instrument adapter/DSO (5-pin) (VAS 5565)

• Multimeter (V.A.G 1715)

• Wrench (T10202)

• Torque wrench (V.A.G 1332)

Special tools, testers and auxiliary items required

• Voltage tester (V.A.G 1527B)

• Vehicle diagnostic tester

• Measuring container, 3 liter

Checking function and voltage supply => [ Function and Voltage Supply, Checking ]

Fuel Delivery, Checking, refer to => [ Fuel Delivery, Checking ]

Checking current draw => [ Current Draw, Checking ]

Fuel Pump (FP) check-valve, checking => [ Fuel Pump Check Valve, Checking ]

Function and Voltage Supply, Checking

• Battery voltage at least 11.5 V

• Fuel pump fuse on the fuse panel OK.

Perform the following:

• The output diagnostic test mode checks the fuel pump.

- Connect the Vehicle Diagnosis Tester - 1 -.

- Connect the diagnostic cable connector - 2 - to the diagnostic connection inside the footwell on the driver side.

- Switch the ignition on.

- On the "OBD" screen, press one button after the other: "01 - engine electronics" and "output diagnostic test mode".

- Press the right arrow button on the display to initiate fuel pump activation.

• Fuel Pump (FP) must run.

• The fuel pump runs quietly.

- Turn off the ignition.

If Fuel Pump (FP) does not start up

- Remove the bench seat. Refer to; Seat Bench, Removing and Installing.

- Remove the cover - 1 - from the fuel delivery unit. Arrow - 2 - points in direction of travel.

- Make sure the connector - arrow - is secure. Pull on the connector without pressing the catch. Repeat the fuel pump functionality test if the connector was not connected correctly.

- Pull on the connector.

- Check the contacts on the connector and on the fuel delivery unit for damage.

- Connect the test instrument adapter/DSO (5-pin) (VAS 5565) to the connector and to the fuel delivery unit.

- Connect a voltage tester (V.A.G 1527 B) to wires - 1 - and - 5 - on the test instrument adapter/DSO (5-pin) (VAS 5565).

- Switch the ignition on.

• LED must light up briefly.

If LED does not light up briefly:

- Locate and repair open circuit in wiring using wiring diagram.

LED lights up briefly (voltage supply OK):

- Remove the fuel delivery unit => [ Fuel Delivery Unit, Removing and Installing ] Service and Repair.

- Check if the electrical wiring between the flange and fuel pump is connected.

If no open circuits are found:

- If the fuel pump is faulty, replace the fuel delivery unit. Refer to => [ Fuel Delivery Unit, Removing and Installing ] Service and Repair.

Fuel Delivery, Checking

• Voltage supply OK.

• Fuel pressure regulator and residual pressure OK => [ Fuel Pressure Regulator and Residual Pressure, Checking ] Fuel Pressure Regulator and Residual Pressure, Checking

• Fuel filter OK.

Perform the following:

- Remove the cover from the fuel filler tube.

- Remove the bench seat. Refer to; Seat Bench, Removing and Installing.

- Remove the cover - 1 - from the fuel delivery unit. Arrow - 2 - points in direction of travel.

- Make sure the connector - arrow - is secure. Pull on the connector without pressing the catch. If the connector was not connected correctly, it could cause a fault.

- Connect the VAG 1348 remote control (V.A.G 1348/3A) to the test instrument adapter/DSO (5-pin) (VAS 5565) and to the positive (+) battery terminal.

• This work step allows the fuel pump to run when the engine is not running.

• The fuel pump delivery rate is measured at 4 bar. Measure the fuel pressure before measuring the delivery quantity. Refer to => [ Fuel Pressure Regulator and Residual Pressure, Checking ] Fuel Pressure Regulator and Residual Pressure, Checking.

Fuel system is under pressure!

• Wear protective goggles and protective clothing in order to avoid injury and contact with the skin.

• Before loosening line connections, place cloths around the connection point. Then release pressure by carefully pulling off the line.

- Remove the return line - 1 - from the fuel pressure regulator.

• Press in securing ring to disengage the fuel line.

- Connect the adapter (VAS 6550/1) to the fuel pressure regulator and hold the end of the adapter in a measuring container.

- (V.A.G 1348/3A) Operate the remote control for approximately 5 seconds to fill the fuel filter.

- Empty measuring container.

- The fuel pump delivery rate depends on the voltage. Therefore, additionally, connect the Multimeter (V.A.G 1715) to the test instrument adapter/DSO (5-pin) (VAS 5565) connectors - 1 - and - 5 -.

- Operate the remote control for 60 seconds while measuring the battery voltage.

- Compare the delivered quantity of fuel with the specified value.

*) Minimum delivery rate cm3/60 s

**) Voltage on the fuel pump with engine running in idle and the pump is on.

Example:

During test, a voltage of 10.5 Volts is measured. This results in a minimum delivery quantity of approximately 1200 cm3/60 s.

If the minimum delivery rate is not attained:

- Check the fuel filter. Proceed as follows:

Fuel system is under pressure!

• Wear protective goggles and protective clothing in order to avoid injury and contact with the skin.

• Before loosening line connections, place cloths around the connection point. Then release pressure by carefully pulling off the line.

- Disconnect the fuel supply line - arrow - from the fuel filter.

- Connect the pressure gauge (VAS 6550) to the fuel supply line with the adapter (VAS 6550/1). Hold the adapter (VAS 6550/2) in the measuring container.

- Make sure the drain is closed and the shut-off valves are open.

- Operate the remote control (V.A.G 1348/3A). Close the shut-off valve - A - slowly until the pressure gauge read 4 bar. From this point on do not move position of shut-off valve.

- Empty measuring container.

- Repeat the fuel delivery test.

If the minimum delivery rate is now obtained:

- Replace the fuel filter.

If minimum delivery rate is again not obtained:

- Remove the fuel delivery unit and check the filter screen for dirt.

Only when up to now no malfunction has been detected:

- Replace the fuel delivery unit => [ Fuel Delivery Unit, Removing and Installing ] Service and Repair.

- Reconnect all disconnected fuel lines.

- Fuel System, Bleeding. Refer to => [ Fuel System, Bleeding ] Service and Repair.

The fuel delivery rate is attained. If a fault in the fuel supply is still suspected (for example, intermittent loss of fuel supply):

- Check fuel pump current draw; refer to => [ Current Draw, Checking ].

Current Draw, Checking

Perform the following:

- Remove the bench seat. Refer to; Seat Bench, Removing and Installing.

- Remove the cover - 1 - from the fuel delivery unit. Arrow - 2 - points in direction of travel.

- Make sure the connector - arrow - is secure. Pull on the connector without pressing the catch. If the connector was not connected correctly, it could cause a fault.

- Connect the current probe - A - to the red cable labeled "current probe" for the test instrument adapter/DSO (5-pin) (VAS 5565).

- Start engine and let run at idle.

- Measure current draw of fuel pump.

• Specified value: max. 9 amps.

• If the malfunction in the fuel system only occurs sporadically, the test can also be performed during a road test. A second person is needed to do this.

If the current draw is exceeded:

- If the fuel pump is faulty, replace the fuel delivery unit. Refer to => [ Fuel Delivery Unit, Removing and Installing ] Service and Repair.

Fuel Pump Check Valve, Checking

Perform the following:

- Remove the bench seat. Refer to; Seat Bench, Removing and Installing.

- Remove the cover - 1 - from the fuel delivery unit. Arrow - 2 - points in direction of travel.

- Make sure the connector - arrow - is secure. Pull on the connector without pressing the catch. If the connector was not connected correctly, it could cause a fault.

- Connect the VAG 1348 remote control (V.A.G 1348/3A) to the test instrument adapter/DSO (5-pin) (VAS 5565) and to the positive (+) battery terminal.

Fuel system is under pressure!

• Wear protective goggles and protective clothing in order to avoid injury and contact with the skin.

• Before loosening line connections, place cloths around the connection point. Then release pressure by carefully pulling off the line.

- Disconnect the fuel supply line - arrow - from the fuel filter.

- Connect the pressure gauge (VAS 6550) to the fuel supply line with the adapter (VAS 6550/1). Hold the adapter (VAS 6550/2) in the measuring container.

- Close the shut-off valve - A - on the pressure gauge (VAS 6550) so the lever is perpendicular to the direction of flow.

- Operate remote control at short intervals, until a pressure of approximately 4 bar has built up.

Danger of spraying when opening shut-off valve.

• Wear protective goggles and protective clothing in order to avoid injury and contact with the skin.

• Hold container in front of free connection of pressure measuring device.

- If pressure builds up too high, lower excess pressure by carefully opening the shut-off valve.

- Observe the pressure drop on the pressure gauge.

• After 10 minutes the pressure must not drop below a 3 bar decrease.

If the pressure drops further:

- Check the connections for leaks.

If no fault is detected in the wiring:

- If the fuel pump is faulty, replace the fuel delivery unit. Refer to => [ Fuel Delivery Unit, Removing and Installing ] Service and Repair.