Fuel Pump (FP), Checking

Check fuel pump

Recommended special tools and equipment







- 3217 ring nut spanner
- V.A.G 1318 pressure gauge
- VAG1318/1 adapter
- VAG1318/10 adapter
- VAG1318/11 adapter
- VAG1318/12 adapter







- VAG1332 torque wrench (40 to 200 Nm)
- VAG1348 quantity comparison tool
- VAG1466 electrical circuit tester
- VAG1527B voltage tester
- VAG1594A connector test kit
- VAG1715 multimeter
- Measuring container
- Wiring diagram

Test requirements







- The respective fuses of Fuel Pump (FP) -G6- must be OK:
- Battery voltage must be at least 11.5 volts.
- All electrical consumers like, for example, lights and rear window heating must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.

Checking function and voltage supply
- Remove luggage compartment floor cover.
- Operate starter briefly. Fuel pump must audibly start up.
- Switch off ignition.

If Fuel Pump (FP) does not start up:
- Remove cover in front of fuse holder.







- Remove fuse 28 from fuse holder.
- Connect VAG1348/3A remote control to Fuel Pump (FP) and B+ at terminal 28a using VAG1348/3-2 remote control connection.
- Operate remote control.

If Fuel Pump (FP) runs:
- Check activation of Fuel Pump (FP) Relay -J17- according to wiring diagram:

If Fuel Pump (FP) does not run:







- Disconnect 4-pin harness connector from flange at fuel tank (arrow).







- Connect VAG1527 diode test lamp to the outer terminals of the connector.
- Operate remote control.
LED must light up.

LED does not light up:
- Locate and repair open circuit using wiring diagram:

LED lights up (voltage supply OK):







- Use 3217 ring nut spanner to remove union nut.
- Check whether electrical wires between flange and Fuel Pump (FP) are connected.

If there are no open circuits:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP) unit, Fuel Pump (FP) unit, removing and installing.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Checking fuel delivery

Test requirements
- Voltage supply OK
- VAG1348/3A remote control connected

Test sequence
- Remove fuel filler cap from fuel filler tube.
- Remove intake manifold cover.







- Open threaded connection (arrow) and catch exiting fuel using a rag.


WARNING:
- The fuel or fuel lines in fuel system can become very hot (danger of scalding)!
- In addition, the fuel system is under pressure! Before opening the system, place rags around the connection area and release pressure by carefully loosening the connection!
- Wear protective goggles and protective gloves when working on the fuel system!







- Connect VAG1318 pressure gauge to fuel supply line using VAG1318/12 adapter.
- Connect hose (VAG1318/1) to adapter (VAG1318/11) of pressure gauge and hold into measuring container.
- Open shut-off valve of pressure gauge. Lever will point in direction of flow -A-.
- Operate remote control and, while doing so, slowly close shut-off valve until pressure gauge displays 3 bar positive pressure. Do not change position of shut-off valve any more.
- Empty the measuring container.
- Delivery rate of Fuel Pump (FP) is dependent on battery voltage. Therefore, connect multimeter to vehicle battery using adapter cables.
- Operate remote control
30 seconds long and measure battery voltage.







- Compare fuel quantity pumped with specified value.

*) Minimum delivery rate Cubic cm/30 s
**) Voltage at fuel pump with engine off and pump running (approx. 2 volts less than battery voltage).

Read-out example:
During test, a voltage of 12.2 volts is measured at battery. Since the voltage at the pump is approx. 2 volts less than battery voltage, there is a minimum delivery rate of 550 cm3/30 s.

If minimum delivery quantity is not obtained:
- Check fuel lines for possible restrictions (kinks) or clogging.







- Disconnect supply line -1- from fuel filter input.
- Connect VAG1318 pressure gauge to hose using VAG1318/10 adapter.
- Repeat test of delivery quantity.

If minimum delivery quantity is now obtained:
- Replace fuel filter.

If minimum delivery quantity is still not obtained:
- Remove Fuel Pump (FP) unit and check filter strainer for dirt.

Only if no malfunctions have been found yet:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP) unit, Fuel Pump (FP) unit, removing and installing.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Delivery rate has been obtained, but malfunctions are still suspected in the fuel supply (e.g. sporadic loss of fuel supply):

Check Fuel Pump (FP) current draw as follows:
- Reconnect all disconnected fuel lines.
- Remove luggage compartment floor cover.







- Connect VAG1715 multimeter with current probe to green/yellow wire from wiring harness.
- Start engine and let run at idle.
- Measure Fuel Pump (FP) current draw.
Specified value: max: 8 amperes


NOTE: If malfunction in fuel system is sporadic, test can also be performed during a road test, but a second person is required.


If current draw is exceeded:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP) unit, Fuel Pump (FP) unit, removing and installing.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Checking Fuel Pump (FP) check-valve

Test requirements
- Remote control connected
- Pressure gauge connected to the fuel supply line of fuel supply tube

Test sequence


NOTE: This test also checks the connections of the fuel supply line from Fuel Pump (FP) unit to connection point of pressure gauge for proper seal.







- Close pressure gauge shut-off valve (lever perpendicular to direction of flow, -position B-).
- Operate remote control in short intervals until a positive pressure of approx. 3 bar has built up.
- If excess pressure is built up, reduce pressure by carefully opening shut-off valve.


WARNING: Danger of spray when opening shut-off valve. Hold container in front of open connection on pressure gauge.


- Observe pressure drop on pressure gauge. Pressure must not fall below
Engine cold 2.2 bar
Engine hot 3.0 bar within 10 minutes.

If pressure drops further:
- Check line connections for proper seal.

If no malfunctions are found in wires:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP) unit, Fuel Pump (FP) unit, removing and installing.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes