Fuel Pump with One Piece Intake Manifold, Checking
Fuel Pump with One Piece Intake Manifold, Checking
=> [ Function and Voltage Supply, Checking ]
=> [ Fuel Pressure, Checking ]
=> [ Residual Pressure, Checking ]
=> [ Fuel Delivery, Checking ]
=> [ Current Draw, Checking ]
Special tools, testers and auxiliary items required
• Wrench (T10202)
• Fuel Injection Pressure Gauge (V.A.G 1318)
• Adapter (V.A.G 1318/6+7)
• Adapter (V.A.G 1318/12)
• Remote Control (V.A.G 1348/3A)
• Multi-Meter (V.A.G 1715)
• Torque Wrench (40-200 Nm) (V.A.G 1332)
• Connector Test Set (V.A.G 1594C)
• Voltage Tester (V.A.G 1527B)
• Measuring Container
• Wiring Diagram
- Read the safety precautions before beginning work. Refer to => [ Safety Precautions ] Fuel Supply.
- Observe the rules for cleanliness. Refer to => [ Clean Working Conditions ] Fuel Supply.
Function and Voltage Supply, Checking
Conditions
• Battery voltage at least 11.5 volts.
• Fuel pump fuse is OK, fuse assignment.
• Fuel pump control module (J538) is OK.
• Low fuel pressure sensor (G410) is OK.
Sequence
- Read the safety precautions before beginning work. Refer to => [ Safety Precautions ] Fuel Supply.
- Observe the rules for cleanliness. Refer to => [ Clean Working Conditions ] Fuel Supply.
- Connect the vehicle diagnostic tester.
- Turn on the ignition.
- Press the following buttons on the vehicle diagnostic tester screen one after another.
Vehicle Self Diagnosis
On Board Diagnosis (OBD) >
01 - Engine Electronics >
Output Diagnostic Test Mode >
- Press the right arrow button on the display until output Diagnostic Test Mode (DTM) of fuel pump electronics.
Fuel pump must now accelerate slowly up to maximum RPM.
- Turn off the ignition.
If fuel pump does not start:
- Fold the rear seat bench forward. On vehicles from 12.06, the rear seat bench must be removed.
- Cut open the carpet on the right side from points - A to B - in the pre-cut area - arrow -.
- Remove the fuel delivery unit cover nuts - 1 - on the right side. It may be necessary to remove the backrest support - 2 - or the support mounting.
- Disconnect the connector from the fuel pump control module (J538) - 5 -.
- Turn the ignition on.
- Check the voltage supply between connector terminals - 3 and 4 - using the (V.A.G 1527B). The Light Emitting Diode (LED) must light up.
- Turn off the ignition.
LED does not light up:
- Locate and repair the open circuit.
LED lights up (voltage supply OK):
CAUTION!
The fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before disconnecting the connection, wrap a cloth around the connection. Then release pressure by carefully disconnecting the connection.
- Disconnect the fuel supply line - 1 -, auxiliary heater fuel line - 2 -, fuel pump connector - 3 - and vent line - 4 -.
• Press in the securing ring to disengage the lines.
- Remove the locking ring using the (T10202).
- Check whether the electrical wires between the flange and fuel pump are connected.
If no open circuits are found:
- Replace the fuel delivery unit if the fuel pump is faulty. Refer to => [ Fuel Delivery Unit and Fuel Level Sensor ] Fuel Delivery Unit and Fuel Level Sensor.
Fuel Pressure, Checking
• Output Diagnostic Test Mode (DTM) activates the fuel pump.
- Read the safety precautions before beginning work. Refer to => [ Safety Precautions ] Fuel Supply.
- Observe the rules for cleanliness. Refer to => [ Clean Working Conditions ] Fuel Supply.
CAUTION!
The fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before disconnecting the connection, wrap a cloth around the connection. Then release pressure by carefully loosening the union nut.
- Lay a cloth around the threaded connection and loosen the union nut - arrow - from the fuel supply hose. To do so, counter hold on the fuel supply line using a wrench.
- Install the (V.A.G 1318) with the (V.A.G 1318/6) and the (V.A.G 1318/7) as shown.
- Open the shut off lever - A - on the (V.A.G 1318).
- Connect the vehicle diagnostic tester.
- Turn on the ignition.
- Press the following buttons on the vehicle diagnostic tester screen one after another.
Vehicle Self-Diagnosis
On Board Diagnosis (OBD) >
01 - Engine Electronics >
Output Diagnostic Test Mode >
- Press the right arrow button on the display until output Diagnostic Test Mode (DTM) of fuel pump electronics.
Fuel pump must now accelerate slowly up to maximum RPM.
Fuel pressure must increase up to a maximum pressure of 6 bar.
If fuel pressure is OK, check the residual pressure. Refer to => [ Residual Pressure, Checking ].
• The fuel pressure decreases to about 5.6 bar after output DTM.
If the specification is exceeded:
- The pressure relief valve in the flange is faulty, replace the flange - item 15 -=> [ Flange ] Description and Operation.
If the specification is not obtained:
- Check the fuel lines for possible restrictions (kinks) or blockages.
- Check all fuel lines in the fuel tank for leaks.
- Check the fuel filter for leaks.
If no malfunction can be found:
- Replace the flange with the pressure relief valve - item 15 -=> [ Flange ] Description and Operation.
- Repeat the test.
If fuel pressure is not obtained again:
- Replace the fuel delivery unit if the fuel pump is faulty. Refer to => [ Fuel Delivery Unit and Fuel Level Sensor ] Fuel Delivery Unit and Fuel Level Sensor.
Residual Pressure, Checking
Conditions
• (V.A.G 1318) still connected.
• Fuel pressure of approximately 5.6 bar is displayed on the (V.A.G 1318), checking. Refer to => [ Fuel Pressure, Checking ].
Sequence
- Watch the pressure decrease on the (V.A.G 1318). After 10 minutes the pressure must not drop below a 4.0 bar decrease.
If the pressure drops further:
- Repeat the fuel pump electronics output Diagnostic Test Mode (DTM). Fuel pressure must increase up to a maximum pressure of 6 bar.
- Immediately close the (V.A.G 1318) shut off lever - arrow -. Lever will then point in position - B -.
• The fuel pressure decreases to about 5.6 bar after output DTM.
If the pressure drops again:
(Leak on engine side)
- Check the connections to the fuel rails and high pressure pump for leaks, refer to => [ Fuel Rail, Injectors and High Pressure Pump Overview ] Fuel Rail, Injectors and High Pressure Pump Overview.
If no malfunction can be found:
- Replace the high pressure pump.
If the pressure no longer drops:
(Leak on fuel tank side)
- Check the fuel filter for leaks.
- Check the fuel lines to the flange - item 15 -=> [ Flange ] Description and Operation for leaks.
- Check all additional fuel lines in fuel tank for leaks.
If no malfunctions are found on fuel line:
- The pressure relief valve inside the fuel delivery unit flange is faulty.
- Replace the flange with pressure relief valve - item 15 -=> [ Flange ] Description and Operation.
Fuel Delivery, Checking
Sequence
- Read the safety precautions before beginning work. Refer to => [ Safety Precautions ] Fuel Supply.
- Observe the rules for cleanliness. Refer to => [ Clean Working Conditions ] Fuel Supply.
- Fold rear seat bench forward. On vehicles from 12.06, the rear seat bench must be removed.
- Cut open the carpet on the right side from points - A to B - in the pre-cut area - arrow -.
- Remove the fuel delivery unit cover nuts - 1 - on the right side. It may be necessary to remove the backrest support - 2 - or the support mounting.
- Disconnect the connector from the fuel pump control module (J538) - 5 -.
- Disconnect the connector - 3 - from the flange on the fuel delivery unit.
- Connect the (V.A.G 1348/3A) with adapter cables from the (V.A.G 1594C) to terminal - 1(+) - of fuel pump and to terminal - 3(+) - of the harness connector for the fuel pump control module.
- Connect terminals - 4(-) - of the harness connector and - 4(-) - of the fuel pump using an adapter cable from (V.A.G 1594C).
CAUTION!
The fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before disconnecting the connection, wrap a cloth around the connection. Then release pressure by carefully loosening the union nut.
- Lay a cloth around the threaded connection and loosen the union nut - arrow - from the fuel supply hose. To do so, counter hold on the fuel supply line using a wrench.
- Install the (V.A.G 1318) with the (V.A.G 1318/6), (V.A.G 1318/7) and (V.A.G 1318/12) as shown.
CAUTION!
Danger of spraying when opening the shut off lever; wear protective goggles and protective clothing to prevent injuries and contact with skin. Hold container in front of free connection of pressure measuring device.
- Open the shut off lever on the (V.A.G 1318). Lever will point in direction of flow - A -.
- Turn the ignition on.
• A second mechanic is needed for the following task.
- Hold the end of the (V.A.G 1318/6) in a measuring container.
- Operate the (V.A.G 1348/3A). Slowly close the shut off lever, until the (V.A.G 1318) shows 4 bar. From this point on do not move the position of the shut off lever.
- Empty the measuring container.
- Operate the (V.A.G 1348/3A) for 15 seconds: the minimum delivery quantity must be 350 cm 3/ 15 seconds
If the minimum delivery rate is not attained:
- Check the fuel lines for possible restrictions (kinks) or blockages.
If the lines are OK:
- Replace the fuel filter. Refer to => [ Fuel Filter ] Removal and Replacement.
- Repeat the test.
If the specified value is again not obtained:
- Replace the fuel delivery unit if the fuel pump is faulty. Refer to => [ Fuel Delivery Unit and Fuel Level Sensor ] Fuel Delivery Unit and Fuel Level Sensor.
Delivery rate has been obtained, but malfunctions are still suspected in the fuel supply (for example, intermittent loss of fuel supply):
- Check the fuel pump current draw. Refer to => [ Current Draw, Checking ].
Current Draw, Checking
- Check the current draw of the fuel pump as follows:
- Reconnect all disconnected fuel lines.
- Connect the (V.A.G 1715) and the current probe to the wire for the 4 pin connector contact - 1 - - arrow - on the right fuel delivery unit wiring harness.
- Start the engine and run at idle speed.
- Measure the current draw of the fuel pump. Specified value: maximum 11 amps
If the current draw is exceeded:
- If the fuel pump is faulty, replace the fuel delivery unit. Refer to => [ Fuel Delivery Unit and Fuel Level Sensor ] Fuel Delivery Unit and Fuel Level Sensor.
• If the malfunction in fuel system is sporadic, test can also be performed during a road test, but a second person is required.