With Manufacturer's Tools
Fuel pump, checking
Engines: AEG, AVH, AZG, BEJ, BEV, BER, BHP
Special tools and equipment
- 3217 Union nut spanner
- VAG 1318 Pressure gauge
- VAG 1318/11 Adapter
- VAG 1318/16 Hose adapter
- VAG 1318/17 Adapter
- VAG 1318/23 Adapter
- VAG 1318/1 Adapter
- VAG 1332 Torque wrench (40 ... 200 Nm)
- VAG 1348/3A Remote control with adapter cable VAG 1348/3-2
- VAG 1466 A Test system
- VAG 1527 B Diode test lamp
- VAG 1594 A Adapter set
- VAG 1715 or Fluke 83 Multimeter
- Measuring container
- Current flow diagram
Requirements
- Fuse No. 28 OK.
- Battery voltage must be at least 11.5 V.
- All electrical consumers, e.g. lights and rear window defroster must be switched off.
- If the vehicle is equipped with air conditioning, this must be switched off.
- On models with an automatic transmission the selector lever must be in position "P" or"N".
Note: Observe description of crash fuel shut-off function.
Checking function and voltage supply
- Remove cover from fuel delivery unit.
- Briefly operate starter.
- Fuel pump must be heard to run
- Switch off ignition.
If the fuel pump does not run:
- Remove cover in front of fuse holder.
- Pull fuse No. 28 out of fuse holder.
- Connect remote control VAG 1 348/3A with adapter cable VAG 1348/3-2 to contact 28a to fuel pump and battery positive (+).
- Operate remote control.
Fuel pump runs:
- Check activation of fuel pump relay referring to wiring diagram:
Fuel pump does not run:
- Take 4-pin connector off flange (arrow).
- Connect diode test lamp VAG 1527 B with auxiliary cables from VAG 1594 A to outer contacts of connector.
- Operate remote control.
LED must light up
If LED does not light up:
- Locate and eliminate open circuit using current wiring diagram:
LED lights up (voltage supply OK.):
- Remove union nut with wrench 3217
- Check electrical wires between flange and fuel pump for continuity.
If no open circuit can be found:
- Fuel pump is faulty, replace fuel delivery unit.
Checking delivery rate
Requirements
- Voltage supply OK.
- Remote control VAG 1348/3A connected.
Work sequence
- Remove filler cap from fuel tank filler neck.
WARNING:
- The fuel system is under pressure! Before opening the system place a cloth around the connection. Then release the pressure by carefully loosening the connection.
- Always wear eye protection and wear fuel resistant gloves when disconnecting system connections.
Engines: AEG, AVH, AZG
- Pull off supply hose -3- (with white marking) and collect fuel which leaks out in a cloth.
Note: To do this, press buttons on hose couplings
Engines: BEJ, BER, BHP, BEV
- Pull off supply hose -1- (with white marking) and collect fuel which leaks out in a cloth.
Note: To do this, press buttons on hose couplings
Continue for all engines
- Connect pressure gauge VAG 1318 with adapter VAG 1318/23 and VAG 1318/17 to fuel supply line.
- Push hose adapter VAG 1318/16 onto adapter VAG 1318/11 on pressure gauge and hold hose in a measuring container.
- Open shut-off tap on pressure gauge. Lever then points in direction of flow -A-.
- Operate remote control VAG 1 348/3A. Then close shut-off tap slowly until pressure gauge shows 3.5 bar pressure. From this point on do not alter setting of shut-off tap.
Engine: BEV approximate 3.5 bar
- Empty measuring container.
- Quantity of fuel delivered by fuel pump depends on battery voltage. Therefore connect multimeter to vehicle battery using adapter cables from VAG 1 594 A.
- Operate remote control for 30 seconds and measure battery voltage.
- Compare quantity of fuel delivered with specification.
- Minimum delivery cm3/30 seconds
- Voltage at fuel pump with engine at rest and pump running (approximately 2 volts less than battery voltage).
Example:
During the test, a voltage of 12.5 volts is measured at the battery. As the voltage at the pump is approximately 2 volts less than the battery voltage, the result is a minimum delivery of approximately 200 cm3/30 seconds.
If the minimum delivery rate is not attained:
- Check fuel lines for possible restrictions (kinks) or blockages.
- Disconnect supply hose -1- off inlet to fuel filter.
Note: To do this, press buttons on hose couplings
- Connect pressure gauge VAG 1318 to hose with adapter VAG 1318/17.
- Repeat delivery rate check.
If minimum delivery rate is now attained:
- Replace fuel filter
If minimum delivery rate is again not attained:
- Remove the fuel delivery unit and check the filter strainer for soiling.
Up to now no fault has been detected:
- Fuel pump defective, replace fuel deliver unit
If delivery quantity has been attained, but nevertheless you suspect a fuel supply system fault (e.g. intermittent failure of fuel supply system):
- Check current draw of the fuel pump as follows:
- Reconnect all disconnected fuel lines.
- Connect multimeter VAG 1715 using the current clamp to the green/yellow wire of wiring harness.
- Start engine and run at idle speed
- Measure current draw of the fuel pump. Specification: max 8 amps.
Note: If the fuel system malfunctions intermittent, the check can be performed during a road test, but a 2nd technician is necessary.
If current consumption is exceeded:
- Fuel pump defective, replace fuel deliver unit.
Checking fuel pump non-return valve
Requirements
- Remote control VAG 1348/3A is still connected
- Pressure gauge VAG 1348 is still connected
With this check the fuel supply line connections from fuel delivery unit to the point at which the pressure gauge VAG 1318 is connected will be checked for leaks at the same time.
- Close pressure gauge shut-off tap (lever at right angles to through flow direction position-Be).
- Operate remote control at short intervals until a pressure of approximately 3 bar has built up.
WARNING: Danger of spray when opening the shut-off trap, hold container before free connection of pressure gauge.
- If pressure builds-up too high, relieve excess pressure by carefully opening shut-off tap.
- Observe pressure drop on gauge. After 10 minutes, pressure must not drop below 2.5 bar.
If the pressure drops further:
- Check line connections for leaks.
If no fault in lines is detected:
- Fuel pump defective, replace fuel deliver unit.