With Manufacturer's Scan Tool
Fuel pump, checking
Special tools and equipment
^ 3217 Union nut wrench
^ 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.G. 1332 Torque wrench (40...200 Nm)
^ V.A.G. 1348/3A Remote control with adapter cable
^ V.A.G. 1348/3-2
^ V.A.G. 1527 B Diode test lamp
^ V.A.G. 1594 A Adapter set
^ V.A.G. 1715 Multimeter
^ Measuring container
^ Wiring diagram
Test conditions
^ Fuse 28 must be OK.
^ Battery voltage must be at least 11.5 V.
^ All electrical consumers, e.g. lights and rear window defogger must be switched off.
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 V.A.G. 1 348/3A with adapter cable V.A.G. 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:
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
Fuel pump does not run:
^ 4-pin connector must be separated from flange on fuel delivery unit.
^ Connect diode test lamp V.A.G. 1527 B with adapter cables from V.A.G. 1594 A to outer contacts of connector.
^ Operate remote control.
^ LED must light up
LED does not light up:
^ Locate and eliminate open circuit referring to wiring diagram:
->Electrical Wiring Diagrams, Troubleshooting & Component Locations
LED lights up (voltage supply OK.):
^ Remove union nut with wrench 3217.
^ Check that electrical wires between flange and fuel pump are connected.
If no open circuit can be found:
^ Fuel pump faulty, replace fuel delivery unit.
Checking delivery rate
Test conditions
^ Voltage supply OK
^ Remote control V.A.G. 1348/3A connected
Test sequence
^ Remove filler cap from fuel tank filler neck.
^ Pull off supply hose -3- (with white marking) and collect fuel that leaks out with a cloth.
Note: Press locking ring inward to release fuel line.
WARNING! Fuel system is under pressure! Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.
^ Connect pressure gauge
^ V.A.G. 1318 with adapter
^ V.A.G. 1318/23 and V.A.G. 1318/17 to fuel supply line.
^ Push hose V.A.G. 1318/16 onto adapter V.A.G. 1318/11 on pressure gauge and hold hose in a measuring container.
^ Open shut-off tap on pressure gauge. Lever then points in flow direction -A-.
^ Operate remote control V.A.G. 1348/3A. Close cut-off tap slowly, until pressure gauge shows 3 bar. From now on do not alter setting of cut off tap.
^ Empty measuring container.
^ Quantity of fuel delivered by fuel pump depends on battery voltage. Therefore, connect multimeter to vehicle battery using adapter cables from V.A.G. 1594 A.
^ Operate remote control for 30 seconds and measure battery voltage.
^ Compare quantity of fuel delivered with nominal value.
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 on the battery. As the voltage at the pump is approximately 2 volts less than the battery voltage, the result is a minimum delivery of 200 cm3/30s.
If the minimum delivery rate is not attained:
^ Check fuel lines for possible restrictions (kinks) or blockages.
^ Pull fuel line -1- off input side of fuel filter.
^ Connect pressure gauge V.A.G. 1318 with adapter 1318/17 to hose.
^ Repeat delivery rate check.
If the minimum delivery rate is now attained:
^ Replace fuel filter.
If the minimum delivery rate is again not attained:
^ Remove fuel delivery unit and check strainer for soiling.
If no faults have been detected up to this point:
^ Replace fuel delivery unit.
If the delivery rate has been attained but a fuel supply system malfunction is still suspected (e.g. intermittent failure of fuel supply system):
^ Check current draw of fuel pump as follows:
^ Reconnect all disconnected fuel lines.
^ Connect multimeter V.A.G. 1715 using current clamp to green/yellow wire of wiring harness.
^ Start engine and run at idling speed.
^ Measure current draw of fuel pump.
Specification: maximum 8 amps
Note: If the fuel system malfunction is intermittent, you can perform the check during a road test with the help of a 2nd person.
If the current draw is exceeded:
^ Fuel pump faulty, replace fuel delivery unit.
Checking fuel pump non-return valve
Test conditions
^ Remote control V.A.G. 1348/3A is still connected.
^ Pressure gauge V.A.G. 1318 is still connected.
Test sequence
Note: With this check the fuel supply line connections from the fuel delivery unit to the point at which the pressure gauge V.A.G. 1318 is connected will be checked for leaks at the same time.
^ Close pressure gauge cut-off tap (lever across flow direction (position -B-).
^ 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-tap; hold container in front of the free connection on the pressure gauge.
^ If pressure builds up too high, lower excess pressure by carefully opening shut-off tap.
^ Observe pressure drop on gauge. Over a duration of 10 minutes pressure must not drop below 2.5 bar.
If the pressure drops further:
^ Check line connections for leaks.
If no wiring fault is detected:
^ Fuel pump faulty, replace fuel delivery unit.