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Fuel Pump Checking



Fuel Pump, Checking

Recommended special tools and equipment







- 3217 ring nut spanner
- V.A.G 1318 pressure gauge
- V.A.G1318/1 adapter
- V.A.G1318/11 adapter
- V.A.G1318/17 adapter
- V.A.G1318/23 adapter







- A.G1332 torque wrench (40 to 200 Nm)
- V.A.G1348 quantity comparison tool
- V.A.G1466 electrical circuit tester
- V.A.G1527B voltage tester
- V.A.G1594A connector test kit
- V.A.G1715 multimeter
- Measuring container
- Wiring diagram

Requirements







- The respective fuses of Fuel Pump (FP) -G6- must be OK.
- Battery voltage must be at least 11.5 volts
- electrical consumers like, lights and rear window heating must be switched off.
- If vehicle is equipped with an A/C system, it must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.

NOTE: Note function description of crash fuel shut-off.

Checking function and voltage supply

NOTE: In continuing the work procedure, it is necessary to disconnect the battery Ground (GND) strap. Determine whether a coded radio is installed. If necessary, determine anti-theft coding first.

- Remove cover from Fuel Pump (FP)
- Operate starter briefly.

Fuel pump must audibly start up.
- Switch off ignition.

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







- Remove fuse 28 from fuse holder.
- Connect V.A.G1348/3A remote control to Fuel Pump (FP) and B+ at terminal 28a using remote control connection (V.A.G1348/3-2).
- 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 connector from flange at Fuel Pump (FP).







- Connect V.A.G1527 diode test lamp to outer terminals of 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.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Checking fuel delivery

Requirements
- Voltage supply OK
- V.A.G1348/3A remote control connected

Test sequence
- Remove fuel filler cap from fuel filler tube.







- Disconnect supply line -1- and catch escaping 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 pressure gauge (V.A.G1318) to fuel supply line using adapters (V.A.G1318/23 and V.A.G1318/17).
- Connect hose (V.A.G1318/1) to adapter (V.A.G1318/11) 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. Slowly close shut-off valve until on pressure gauge
3 bar positive pressure is indicated. Do not change position of shut-off valve any more.
- Empty 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 cu.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 12.5 volts is measured at battery. Since voltage at the pump is approx. 2 volts less than battery voltage, there is a minimum delivery rate of 200 cu.cm/30 s.

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







- Disconnect supply line -1- from fuel filter input.
- Connect pressure gauge (V.A.G1318) with adapter (1318/17) to hose.
- Repeat test of delivery quantity.

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

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

Only if no malfunctions have been found yet:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP) unit.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. 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:
- Re-connect all disconnected fuel lines.







- Connect multimeter (V.A.G1715) with electrical current probe to wire of 4-pin connector (terminal 1 arrow) 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.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Checking Fuel Pump (FP) check-valve

Requirements
- V.A.G1348/3A remote control is still connected.
- V.A.G1318 pressure gauge is still connected.

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.

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

- If excess pressure is built up, reduce pressure by carefully opening shut-off valve.
- Observe pressure drop on pressure gauge. Pressure must not fall below 2.5 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.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
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