With Manufacturer's Scan Tool
Fuel pump, checking
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 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 D lode test lamp
^ VAG 1594 A Adapter set
^ VAG 1715 Multimeter
^ Measuring container
^ Wiring diagram
Test conditions
^ Fuse 28 must be OK.
^ The 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.
^ Selector lever must be in position "P" or "N" on vehicles with an automatic transmission.
Note: See functional description of crash fuel shut-off , Refer to inertia Fuel Shutoff Switch, Description and Operation
Checking function and voltage supply
- Fold rear seat bench forward.
- Remove cover from fuel delivery unit.
- Briefly operate starter.
Fuel pump must audibly run.
- Switch ignition off.
If the fuel pump does not run:
- Remove cover in front of fuse holder.
- Pull fuse No. 28 (for fuel pump) out of fuse holder.
- Connect remote control VAG 1 348/3A to contact 28a to fuel pump and battery positive (+) using adapter cable VAG 1348/3-2.
- Operate remote control.
Fuel pump runs:
- Check activation of Fuel Pump (FP) relay-J17-with VA. 1466A referring to wiring diagram:
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
Fuel pump does not run:
- Remove 4-pin connector from flange -arrow-.
- Connect diode test lamp VAG 1527 B to outer contacts of connector using adapter cables from VAG 1594 A
- Operate remote control.
LED must light up
LED does not light-up:
- Locate and eliminate open circuit referring to wiring diagram:
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations LED lights up (voltage supply OK ):
- Remove union nut with spanner 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, Refer to Fuel Delivery Valve Assembly, Service and Repair.
Checking delivery rate
Test conditions
^ Voltage supply OK.
^ Remote control VAG 1 348/3A connected.
Test sequence
- Remove filler cap from fuel tank filler neck.
- Disconnect supply hose -3- (with white marking) and collect fuel that may leak out with a cloth.
Note: Press buttons on hose couplings to do so.
WARNING: Fuel supply lines are under pressure! Before removing from hose connections wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
- Connect pressure gauge VAG 1318 to fuel supply pipe using adapter VAG 1318/23 and VAG 1318/17.
- Push hose adapter VAG 1318/16 onto adapter VAG 1318/1 1 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 VAG 1 348/3A. Close shut-off tap slowly, until pressure gauge shows 3 bar. From now on do not alter setting of shutoff tap.
- Empty measuring container.
The quantity of fuel delivered by the fuel pump depends on the battery voltage.
- 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 nominal value.
*) Minimum delivery cm3/30 seconds
**) Voltage at fuel pump with engine not running and pump running (approximately 2 volts less than battery voltage).
Example:
During the test, a voltage of 12.2 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 200 cm3/30 seconds.
If the minimum delivery rate is not attained:
- Check fuel pipes for possible restrictions (kinks) or blockages.
- Disconnect fuel line -1- from input side of fuel filter.
Note: Press buttons on hose couplings to do so.
- Connect pressure gauge VAG 1318 to hose using adapter 1318/17.
- Repeat delivery rate test.
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 filter for soiling.
Only if no faults have been detected up to now:
- Fuel pump faulty, replace fuel delivery unit, Refer to Fuel Delivery Valve Assembly, Service and Repair
If the delivery rate has been attained but a fuel supply system fault 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 VAG 1715 to wire -arrow- for contact 1 of 4-pin connector using current pick-up clamp.
- Start engine and run at idling speed.
- Measure current draw of fuel pump.
Specification: max. 8 amps.
Note: If the fuel system malfunction is intermittent, perform the check during a test drive with the assistance of a 2nd person.
If the current draw is exceeded:
- Fuel pump faulty, replace fuel delivery unit, Refer to Fuel Delivery Valve Assembly, Service and Repair
Checking fuel pump non-return valve
Test conditions
^ Remote control VAG 1 348/3A is still connected.
^ Pressure gauge VAG 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 VAG 1318 is connected will be checked for leaks at the same time.
- Close pressure gauge shut-off tap (lever across flow direction -position B-).
- Operate remote control at short intervals, until a pressure of approximately 3 bar has built up.
- If pressure builds up too high, lower excess pressure by carefully opening shut-off tap.
WARNING: Danger of spray when opening the shut-off-tap; hold container in front of the free connection on the pressure gauge.
- Observe pressure drop on gauge. Over a duration of 10 minutes pressure must not drop below a 2.5 bar decrease.
If the pressure drops further:
- Check pipe connections for leaks.
If no wiring fault is detected:
- Fuel pump faulty, replace fuel delivery unit, Refer to Fuel Delivery Valve Assembly, Service and Repair