Fuel Pump (FP) In Fuel Tank, Check

Check Fuel Pump (FP) in fuel tank

Recommended special tools and equipment







- 3087 special wrench for tank sensor
- V.A.G 1318 pressure gauge
- VAG1318/10 adapter
- VAG1318/11 adapter
- V.A.G 1318/16 hose adapter
- VAG1331 torque wrench (5 to 50 Nm)







- VAG1332 torque wrench (40 to 200 Nm)
- VAG1348/3A remote control with
- VAG1348/3-2 adapter cable
- VAG1594A connector test kit VAG1715 multimeter
- VAS5024A assembly tool for spring-type clamps

Without illustration:
- Measuring container
- Wiring diagram

Test requirements







- The respective fuses of Fuel Pump (FP) -G6- must be OK:







- Fuses -1, 2, 3, 4 and 7- in protective housing (plenum chamber, left) must be OK.
- Battery voltage must be at least 11.5 Volts.
- All electrical consumers such as, for example, lights and rear window defroster must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.

Checking function and voltage supply
- Fold the rear seatback down.
- Remove cover from Fuel Pump (FP)
- Operate starter briefly. Fuel pump must audibly start up.
- Switch ignition off.

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







- Remove fuse 28 for the Fuel Pump (FP) 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):
- Remove fuel pump.
- 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), Fuel Pump (FP), 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
- Remote control connected

- 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 VAG1318 pressure gauge to fuel supply line using VAG1318/10 adapter.
- Connect hose (VAG1318/16) to adapter (VAG1318/11) of pressure gauge and hold it in 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 4 bar positive pressure is indicated. 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 (FP) 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 Cubic cm/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 pressure gauge (VAG1318) with adapter (1318/10) to hose.
- Repeat test of delivery quantity.

If minimum delivery quantity is now obtained:
- Replace fuel filter, Fuel filter, removing and installing

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.

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.







- Connect multimeter with current probe to green/yellow wire of 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. 4 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