Fuel Pump: Testing and Inspection

Fuel Pump (FP), Checking

Recommended special tools and equipment
- V.A.G 1318 pressure gauge
- V.A.G 1318/11 adapter
- V.A.G 1318/16 hose adapter
- V.A.G 1318/17 adapter
- V.A.G 1318/23 adapter
- V.A.Q1332 VJLG134U3A

- V.A.G1332 torque wrench (40 to 200 Nm)
- V.A.G 1348/3A remote control with V.A.G 1348/3-2 adapter cable
- V.A.G1466 electrical circuit tester
- V.A.G 1527B voltage tester
- V.A.G 1594A connector test kit
- V.A.G 1715 multimeter
- Measuring container
- Wiring diagram

Requirements

- Fuse no. 28 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 position -P- or -N-

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

Observe safety precautions.
Observe rules for cleanliness.

Checking function and voltage supply
- Fold rear seatback forward.
- 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 no. 28 from fuse holder.
- Connect V.A.G1348/3A remote control to Fuel Pump (FP) and B+ at terminal 28a using V.A.G1348/3-2 remote control connection.
- Operate remote control.

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

If Fuel Pump (FP) does not run:

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

- Connect V.A.G 1527 B voltage tester 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 wrench 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. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Checking fuel delivery quantity

Requirements
- Voltage supply OK
- V.A.G 1348/3A remote control connected

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

- Disconnect supply line -3- (black with white marking) and catch escaping fuel using a rag.

NOTE: Press in securing ring to disengage the fuel lines.

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 to fuel supply line using adapter V.A.G 1318/23 and V.A.G 1318/17.
- Connect hose V.A.G1318/16 to adapter V.A.G1318/11 of pressure gauge and hold it in measuring container.
- Open shut-off valve of pressure gauge. Lever will point in direction of flow -A-.

Vehicles with engine code AEG, AVH, AZG, BDC
- Operate V.A.G 1348/3A remote control. Slowly close shut-off valve until 3 bar of positive pressure is indicated on pressure gauge. Do not change position of shut-off valve.

Vehicles with engine code BEV, BGD
- Operate V.A.G 1348/3A remote control. Slowly close shut-off valve until 3.5 bar positive pressure is indicated on pressure gauge. Do not change position of shut-off valve any more.

Continued for all vehicles
- 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 (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 200 cu.cm/30 s.

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

Vehicles with engine code AEG, AVH, AZG, BDC

- Disconnect supply line -1- from fuel filter input.

NOTE: Depress buttons on hose connections to do so.

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 with adapter 1318/17 to hose.

Continued for all vehicles
- Repeat test of delivery rate.

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

Vehicles with engine code BEV, BCD
- Bleed fuel system.

Continued for all vehicles
If minimum delivery rate 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.
- Re-connect all disconnected fuel lines.

Vehicles with engine code BEV, BCD
- Bleed fuel system.

Continued for all vehicles
- 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 current pick-up of Fuel Pump (FP).

Current pick-up of Fuel Pump (FP)

- Connect multimeter 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 pick-up 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. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Fuel Pump (FP) check-valve, checking

Requirements
- Remote control is still connected.
- Pressure gauge is still connected.

Work sequence

NOTE: This test also checks the connections of the fuel supply line from Fuel Pump (FP) to connection point of V.A.G 1318 pressure gauge for proper seal.

- Close pressure gauge shut-off valve (lever perpendicular to direction of flow -position B-).

Vehicles with engine code AEG, AVH, AZG, BDC
- Operate remote control in short intervals until a positive pressure of approx. 3.0 bar has built up.

Vehicles with engine code BEV, BCD
- Operate remote control in short intervals until a positive pressure of approx. 3.5 bar has built up.

Continued for all vehicles
- 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 free connection on pressure gauge.

Vehicles with engine code AEG, AVH, AZG, BDC
- Observe pressure drop on pressure gauge.
Pressure must not fall below 2.5 bar.

Vehicles with engine code BEV, BGD
- Observe pressure drop on pressure gauge.
Pressure must not fall below 3.0 bar.

Continued for all vehicles
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.
- Re-connect all disconnected fuel lines.

Vehicles with engine code BEV, BGD
- Bleed fuel system.

Continued for all vehicles
- 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