With Manufacturer's Scan Tool
Fuel pump, checking
Special tools and equipment
- 3087 Fuel tank sender spanner
- 3217 Union nut spanner
- VAG 1318 Pressure tester
- VAG 1318/10 Adapter
- VAG 1318/11 Adapter
- VAG 1318/12 Adapter
- VAG 1332 Torque wrench (40-200 Nm)
- VAG 1 348/3A Remote control with VAG 1348/3- 2 Adapter cable
- VAG 1466 Test system
- VAG 1527 B Diode test lamp
- VAG 1594 A Adapter set
- VAG 1715 Multimeter
- Measuring container
- Wiring diagram
Vehicles with all wheel drive
- Fuel tank sender spanner 3087
Vehicles with front wheel drive
- Union nut spanner 3217
Check conditions
- Battery voltage at least 11.5 V
- Fuse No.28 OK.
Checking function and voltage supply
Vehicles with all wheel drive
- Remove rear seat bench.
- Remove cover in floor.
Vehicles with front wheel drive
- Remove floor cover.
Continued for all vehicles
- Briefly operate starter. Fuel pump must be audible.
- Switch ignition off.
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 pumps run:
- Check activation of fuel pump relay
Fuel pump does not run:
- Pull 4-pin connector off fuel tank flange -arrow-.
- Connect diode test lamp VAG 1527 with auxiliary cables from VAG 1594 to outer contacts of connector.
- Operate remote control. LED must light up
LED does not light up:
- Locate and eliminate open circuit using wiring diagram
LED lights up (voltage supply OK.):
Vehicles with all wheel drive
- Remove locking ring with key 3087.
Vehicles with front wheel drive
- Remove union nut with spanner 3217.
Continued for all vehicles
- Check that electrical wires between flange and fuel pump are connected.
If no open circuit can be found:
- Fuel pump malfunctioning. Replace fuel delivery unit, Service and Repair
Checking delivery rate
Check conditions
- Voltage supply OK.
- Remote control VAG1348/3A connected.
Test sequence
- Remove filler cap from fuel tank filler neck.
- Remove intake manifold cover.
- Open threaded union -arrow- and catch escaping fuel with a cloth.
WARNING! Fuel supply lines are under pressure! Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
- Connect pressure gauge VAG 1318 with adapter 1318/12 to fuel supply line.
- Push hose (commercially available) onto adapter VAG 1318/11 of pressure gauge and hold hose in a measuring container.
- Open pressure gauge shut-off tap. Lever then points in through flow direction -A-.
- Operate remote control VAG 1348/3A and slowly close shut-off tap, until pressure gauge shows 4 bar. From this point on do not move position of shut-off tap.
- Empty measuring container.
- Fuel pump delivery range is dependent upon battery voltage. Therefore connect multimeter with adapter cables from VAG 1594 to vehicle battery.
- 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 stationary and pump running (approx. 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 approx. 2 volts less than the battery voltage then this will equate to a minimum delivery of 550 cm3/30 5.
If the minimum delivery rate is not attained:
- Check fuel lines for possible restrictions (kinks) or blockages.
Vehicles with all wheel drive
- Pull supply hose -1 - off inlet to fuel filter.
Vehicles with front wheel drive
- Pull supply hose -1 - off inlet to fuel filter.
Continued for all vehicles
- Connect pressure gauge VAG 1318 to hose with adapter 1318/10.
- 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 fuel strainer for dirt.
Only when up to now no malfunction has been detected:
- Fuel pump malfunctioning. Replace fuel delivery unit, Service and Repair
If the delivery rate has been attained but nevertheless you suspect a fuel supply system fault (e.g. intermittent failure of fuel supply system):
- Check current draw of fuel pump as follows:
- Reconnect all disconnected fuel lines.
Vehicles with all wheel drive
- Remove rear seat bench.
- Remove cover in floor.
Vehicles with front wheel drive
- Remove floor cover.
Continued for all vehicles
- Connect multimeter VAG 1715 with current clamp on green/yellow wire in wiring harness.
- 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, you can perform the check during a test drive, to do this a 2nd person is necessary.
If the current draw is exceeded:
- Fuel pump malfunctioning. Replace fuel delivery unit, Service and Repair
Checking fuel pump non-return valve
Check conditions
- Remote control VAG 1348/3A connected
- Pressure gauge VAG 1318 connected to hose on fuel supply line.
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 at right angles to throughtlow direction - position -B-).
- Operate remote control at short intervals, until a pressure of approx. 4 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 over the pressure gauge free connection.
- Watch pressure drop on gauge. After 10 minutes pressure must not drop below 2.2 bar (engine cold) or 3.0 bar (engine warm).
If the pressure drops further:
- Check line connections for leaks.
If no wiring malfunction is detected:
- Fuel pump malfunctioning. Replace fuel delivery unit Service and Repair