Fuel Pump, Checking
Fuel Pump, Checking
Special tools, testers and auxiliary items required
• Wrench (T10202)
• Fuel injection pressure gauge (VAG 1318)
• Pressure gauge adapter (VAG 1318/1)
• Adapter (VAG 1318/11)
• Hose adapter (VAG 1318/16)
• Adapter set (VAG 1318/17A)
• Fuel line feed adapter (VAG 1318/23)
• Torque wrench 40-200 Nm (VAG 1332)
• Remote control (VAG 1348/3A)
• Connector test set (VAG 1594C)
• Multi-meter (VAG 1715)
• Test instrument adapter/DSO (5-pin) (VAS 5565)
• Voltage tester (VAG 1527B)
• Vehicle diagnosis, testing and information system (VAS 5051B)
• Measuring container
• Wiring diagram
• Read the safety precautions before beginning work. Refer to --> [ Safety Precautions ] .
• Observe the rules for cleanliness, refer to --> [ Clean Working Conditions ] .
--> [ Function and Voltage Supply, Checking ]
--> [ Fuel Pressure, Checking ]
--> [ Residual Pressure, Checking ]
--> [ Delivery Quantity, Checking ]
--> [ Current Draw, Checking ]
Function and Voltage Supply, Checking
Test Conditions
• Battery voltage at least 12.0 V.
• Fuse No. SC 27 in the fuse block OK
• Fuel pump control module - 2 - OK.
Test Sequence
• The output Diagnostic Test Mode (DTM) checks the function of the fuel pump.
- Connect the (VAS 5051B) - 1 - as follows:
- Connect the diagnostic cable - 2 - to the Data Link Connector (DLC) in the driver footwell.
- Turn on ignition.
- On the following screens, select:
Vehicle Self-Diagnosis
01 - Engine Electronics >
Output Diagnostic Test Mode >
- Press the right arrow button arrow button on the display until output Diagnostic Test Mode (DTM) of fuel pump electronics.
• The fuel pump must now accelerate slowly up to maximum RPM.
• The fuel pump runs quietly.
- Turn off the ignition.
If the fuel pump does not run:
- Remove the rear seat bench.
- Disconnect the electrical connector - arrow - from the fuel pump control module.
- Check the voltage supply between terminals - 1 - and - 6 - using the (VAG 1527B).
• Light Emitting Diode (LED) must light up.
LED does not light up:
- Locate and repair the open circuit in the wiring using the wiring diagram.
LED lights up (voltage supply OK):
- Remove the cover - 1 - with the fuel pump control module - 2 - from the fuel delivery unit.
• When installing the cover - 1 - be sure to pay attention to the installed position: The arrow - 3 - points in the direction of vehicle travel.
CAUTION!
• The fuel supply line is under pressure. Wear protective goggles and protective clothing to prevent injuries and contact with skin.
• Before disconnecting, place a cloth around the connection point. Then release pressure by carefully disconnecting the connection.
- Disconnect the electrical connector - 1 -, black supply line - 2 - and blue return line - 3 -.
• Press in the securing ring to disengage the fuel lines.
- Seal the lines so that the fuel system is not contaminated by dirt etc.
- Remove the locking ring using the (T10202) and raise the fuel delivery unit slightly.
- Check if the electrical wiring between the fuel delivery unit and the fuel pump is connected.
If no open circuits are found:
- The fuel pump is faulty, replace the fuel delivery unit. Refer to --> [ Fuel Delivery Unit ] .
Fuel Pressure, Checking
Test Conditions
• Function and voltage supply for the fuel pump is OK, checking, refer to --> [ Function and Voltage Supply, Checking ].
Test Sequence
CAUTION!
• The fuel supply line is under pressure. Wear protective goggles and protective clothing to prevent injuries and contact with skin.
• Before disconnecting, place a cloth around the connection point. Then release pressure by disconnecting the connection.
- Disconnect the fuel supply line - 3 - at the supply location and catch any leaking fuel with a cloth.
• Pull the circlip upward to unlock the fuel line.
- Install the (VAG 1318) with the (VAG 1318/17A).
- Open the shut off lever on the (VAG 1318). The lever points in the direction of flow.
- Turn the ignition on and off often until the fuel pressure on the (VAG 1318) no longer rises.
- Read off the fuel pressure on the (VAG 1318):
• Specified value: 3.5 to 6.0 bar.
If the fuel pressure is OK, check the retaining pressure, refer to --> [ Residual Pressure, Checking ].
If the specification is exceeded:
- Check the return line between the fuel filter and the fuel pump for kinks or a blockage.
• Fuel tank and attachments assembly overview. Refer to --> [ Fuel Tank and Attachments Assembly Overview ] .
If no malfunction can be found:
- The pressure relief valve in the fuel filter malfunctioning, replace the fuel filter. Refer to --> [ Fuel Filter ] .
If the specification is not obtained:
- Check the fuel pressure in front of the fuel filter. Connect the (VAG 1318) and the (VAG 1318/17A) between the fuel filter and the fuel supply line.
- Open the shut off lever on the (VAG 1318). The lever points in the direction of flow.
- Start the engine and run at idle speed.
CAUTION!
The shut off lever must only be closed slowly. At a fuel pressure of 8 bar, shut off valve must be opened again immediately to prevent damage to the (VAG 1318).
- Slowly close the shut off lever on the (VAG 1318). The lever then points perpendicular to the flow direction - arrow -:
• Pressure must increase to a min. 6.0 bar.
When 6 bar is reached:
- Open the shut off lever immediately!
If pressure has increased:
- The fuel pump is OK. The pressure relief valve in the fuel filter is malfunctioning, replace the fuel filter. Refer to --> [ Fuel Filter ] .
If pressure does not increase:
- The fuel pump is faulty, replace the fuel delivery unit. Refer to --> [ Fuel Delivery Unit ] .
Residual Pressure, Checking
Test Conditions
• Fuel pressure is OK and the (VAG 1318) is connected. Refer to --> [ Fuel Pressure, Checking ].
Test Sequence
- Turn the ignition on and off often until the fuel pressure on the (VAG 1318) no longer rises.
- Read off the fuel pressure on the (VAG 1318):
• Specified value: 3.5 to 6.0 bar.
- Watch the pressure drop on the (VAG 1318) :
• After 10 minutes the pressure must not drop below a 3.0 bar decrease.
If the pressure drops further:
- Turn the ignition on and off often until the fuel pressure on the (VAG 1318) no longer rises.
- After the pressure has built up, immediately close the shut off lever on the (VAG 1318). The lever then points perpendicular to the flow direction - arrow -.
If the pressure drops again:
- Check the high pressure pump fuel pipe for leaks. Refer to --> [ High Pressure Pump with Fuel Pressure Regulator Valve Assembly Overview ] .
If no malfunction can be found:
- Replace the high pressure pump. Refer to --> [ High Pressure Pump ] .
If pressure no longer drops now:
- Check the fuel filter fuel supply line for leaks.
• Fuel tank and attachments assembly overview. Refer to --> [ Fuel Tank and Attachments Assembly Overview ] .
If no malfunctions are found on the fuel supply line:
- Check the check valve in the fuel delivery unit. Connect the (VAG 1318) and the (VAG 1318/17A) between the fuel filter and fuel supply line.
- Open the shut off lever on the (VAG 1318). The lever points in the direction of flow.
- Turn he ignition on and off often until the fuel pressure on the (VAG 1318) no longer rises.
- Read off the fuel pressure on the (VAG 1318):
• Specified value: 3.5 to 6.0 bar.
- After the pressure has built up, immediately close the shut off lever on the (VAG 1318). The lever then points perpendicular to flow direction - arrow -.
- Watch the pressure drop on the (VAG 1318):
• After 10 minutes the pressure must not drop below a 3.0 bar decrease.
If the pressure drops:
- The check valve in the fuel pump is faulty, replace the fuel delivery unit. Refer to --> [ Fuel Delivery Unit ] .
If the pressure does not drop:
- The pressure relief valve in the fuel filter is malfunctioning, replace the fuel filter. Refer to --> [ Fuel Filter ] .
Delivery Quantity, Checking
Test Conditions
• Function and voltage supply for the fuel pump is OK, checking, refer to --> [ Function and Voltage Supply, Checking ].
• Fuel pressure is OK, checking, refer to --> [ Fuel Pressure, Checking ].
Test Sequence
- Remove the rear seat bench.
- Remove the cover - 1 - with the fuel pump control module - 2 - from the fuel delivery unit.
• When installing the cover - 1 - be sure to pay attention to the installed position: The arrow - 3 - points in the direction of vehicle travel.
- Disconnect the electrical connector - arrow - from the fuel delivery unit.
- Connect the (VAS 5565) between the wire harness connector and the fuel delivery unit connector.
- Connect the (VAG 1348/3A) to the (VAS 5565) and to the battery positive terminal.
• This step is needed only to enable the fuel pump to run while the engine is shut off.
- Remove fuel filler cap from fuel filler tube.
CAUTION!
• The fuel supply line is under pressure. Wear protective goggles and protective clothing to prevent injuries and contact with skin.
• Before disconnecting, place a cloth around the connection point. Then release pressure by carefully disconnecting the connection.
- Disconnect the fuel supply line - 3 - at the supply location and catch any leaking fuel with a cloth.
• Pull the circlip upward to unlock the fuel line.
- Connect the (VAG 1318) with the (VAG 1318/23) and the (VAG 1318/17A) to the fuel supply line.
- Connect the (VAG 1318/16) to the (VAG 1318/11) installed on the (VAG 1318) and hold it in a measuring container.
CAUTION!
• Danger of spraying when opening the shut off lever; wear protective goggles and protective clothing to prevent injuries and contact with skin.
• Hold the measuring container in front of the free connection of (VAG 1318).
- Open the shut off lever on the (VAG 1318). The lever will point in direction of flow - A -.
- Operate the (VAG 1348/3A). Slowly close the shut off lever, until the (VAG 1318) shows 4 bar. From this point on do not move the position of the shut off lever.
- Empty the measuring container.
- The quantity of fuel delivered by the fuel pump is dependent upon battery voltage. Connect the (VAG 1715) to electrical connectors - 1 and 5 - on the (VAS 5565).
- Operate the (VAG 1348/3A) for 30 seconds and simultaneously measure the battery voltage.
- Compare the quantity of fuel delivered with specification.
*) Minimum delivery rate cm3/30 s
**) Voltage at the fuel pump with the engine off and the pump running (approximately 2 volts less than the battery voltage).
Example
During the test, a voltage of 12.5 volts is measured at the battery. Since the voltage at the pump is approximately 2 volts less than battery voltage, there is a minimum delivery rate of approximately 580 cm3/30 s.
If the minimum delivery rate is not attained:
- Check the fuel lines for possible restrictions (kinks) or blockages.
• Fuel tank and attachments assembly overview. Refer to --> [ Fuel Tank and Attachments Assembly Overview ] .
If no malfunction can be found:
CAUTION!
• The fuel supply line is under pressure. Wear protective goggles and protective clothing to prevent injuries and contact with skin.
• Before disconnecting, place a cloth around the connection point. Then release pressure by carefully disconnecting the connection.
- Disconnect the fuel supply line - 1 - from the fuel filter input.
• Press in the securing ring to disengage the fuel line.
- Connect the (VAG 1318) and the (VAG 1318/17A) to the fuel supply line - 1 -.
- Resume testing the delivery quantity.
If the minimum delivery rate is now obtained:
- Replace the fuel filter. Refer to --> [ Fuel Filter ] .
If the minimum delivery rate is again not obtained:
- Remove the fuel delivery unit. Refer to --> [ Fuel Delivery Unit ] .
- Check the filter strainer for contamination.
Only when up to now no malfunction has been detected:
- Replace the fuel delivery unit.
If the delivery rate has been attained but nevertheless you suspect a fuel supply system malfunction (for example, intermittent failure of fuel supply system):
- Check the fuel pump current draw. Refer to --> [ Current Draw, Checking ].
Current Draw, Checking
Test Conditions
• Function and voltage supply for the fuel pump is OK, checking, refer to --> [ Function and Voltage Supply, Checking ].
• Connect all fuel lines.
Test Sequence
- Remove the rear seat bench.
- Remove the cover - 1 - with the fuel pump control module - 2 - from the fuel delivery unit.
• When installing the cover - 1 - be sure to pay attention to the installed position: The arrow - 3 - points in the direction of vehicle travel.
- Disconnect the electrical connector - arrow - from the fuel delivery unit.
- Connect the (VAS 5565) to the wire harness connector and the fuel delivery unit connector.
- Connect the current clamp - A - to the red wire (with the words "current clamp" on it) on the (VAS 5565).
- Start the engine and run at idle speed.
- Measure the fuel pump current draw:
• Specified value: Max. 9 amps.
• If the malfunction in the fuel system is sporadic, the test can also be performed during a road test, but a second person is required.
• Observe the safety precautions that apply to road tests. Refer to --> [ If special testing equipment is required during road test, note the following: ] .
If the current draw is exceeded:
- the fuel pump is faulty, replace the fuel delivery unit. Refer to --> [ Fuel Delivery Unit ] .