Fuel Pump (FP), Checking
Fuel Pump (FP), checking
Recommended special tools and equipment
- V.A.G1348/3A Remote control with V.A.G1348/3-2 Adapter cable
- V.A.G1527B Voltage tester
- V.A.G1594A Connector test kit
- 3217 Ring nut spanner
- V.A.G 1318 Pressure gauge
- V.A.G 1318/1 Adapter
- V.A.G 1318/10 adapter
- V.A.G 1318/11 adapter
Not illustrated:
- Measuring container
- Wiring diagram
Test requirements
- Fuse no. 18 for Fuel Pump (FP) must be OK.
- Battery voltage must be at least 11.5 volts.
- All electrical consumers such as lights and rear window defroster must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in -P-.
Note: Note function description of crash fuel shut-off, vehicles 09.99 >
Test sequence
- Switch on ignition.
Fuel Pump (FP) must briefly run audibly.
If Fuel Pump (FP) does not start up:
- Switch ignition off.
- Remove Fuel Pump (FP) Relay -J17- from relay carrier (relay position 12).
Note: Remove battery Ground (GND) strap if tools are necessary for removal of relays or control modules from the relay carrier.
Obtain radio code for radios with anti-theft coding before disconnecting battery.
Do not use metallic tools to pry off relays from relay carrier. The terminals could conduct electricity.
- Connect V.A.G 1348/3A remote control with V.A.G1348/3-2 remote control connection to terminal 4 and B+.
- 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:
- Remove cover from Fuel Pump (FP)
- Disconnect connector from flange on fuel tank.
- Connect 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)
- Erase DTC memory of Engine Control Module (ECM).
- Generate readiness code.
Checking fuel delivery
Test requirements
- Voltage supply OK
- V.A.G1348/3A remote control connected
Test sequence
- Remove fuel filler cap from fuel filler tube.
- Disconnect fuel supply line from fuel rail.
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.G 1318) with adapter (V.A.G 1318/10) to fuel supply line -1-.
- Connect V.A.G 1318/1 hose to V.A.G 1318/11 adapter of pressure gauge and hold in a measuring container.
- Open pressure gauge shut-off valve. 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. Connect multimeter to vehicle battery using adapter cables.
- Operate remote control
30 seconds long.
Compare fuel quantity pumped with specified value.
*) Minimum delivery rate cm3/30 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 12.5 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 530 cm3/30 s.
If minimum delivery rate is not obtained:
- Check fuel lines for possible restrictions (kinks) or clogging.
- Disconnect supply hose -1- from fuel filter input.
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 V.A.G 1318 pressure gauge with V.A.G 1318/10 adapter 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)
- Erase DTC memory of Engine Control Module (ECM)
- Generate readiness code
Delivery rate has been obtained, but malfunctions are still suspected in the fuel supply (e.g. sporadic loss of fuel supply):
- Reconnect all disconnected fuel lines.
- Check current pick-up of Fuel Pump (FP).
Current pick-up of Fuel Pump (FP), checking
- Connect multimeter with current probe to red/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).
- Erase DTC memory of Engine Control Module (ECM)
- Generate readiness code.
Fuel Pump (FP) check-valve, checking
Test requirements
- Remote control is still connected.
- 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. 3.0 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 2 bar.
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)
- Re-connect all disconnected fuel lines.
- Erase DTC memory of Engine Control Module (ECM)
- Generate readiness code.