Fuel Pump, Checking - II

Fuel Pump, Checking







Special tools, testers and auxiliary items required
- Ring nut spanner 3217
- Pressure tester V.A.G 1318
- Adapter V.A.G 1318/11
- Adapter V.A.G 1318/16
- Adapter V.A.G 1318/17
- Adapter V.A.G 1318/23







Special tools, testers and auxiliary items required
- Torque wrench V.A.G 1332
- Remote control V.A.G 1348/3A with adapter cable V.A.G 1348/3-2
- Test system V.A.G 1466
- Diode test lamp V.A.G 1527 B
- Adapter set V.A.G 1594 A
- Multimeter V.A.G 1715
- Measuring container
- Wiring diagram

Requirements







- Fuse No. 28 OK.
- The battery voltage must be at least 11.5V.
- All electrical consumers, e.g. lights and rear window heating, must be switched off.
- If the vehicle is equipped with an air conditioning system, it must be switched off.
- If vehicle has an automatic transmission, move selector lever to "P" or "N".

NOTE: Observe functional description for fuel crash shut-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 over fuse holder.







- Pull fuse No. 28 out of fuse holder.
- Connect remote control V.A.G 1348/3A with adapter cable V.A.G 1348/3-2 to contact 28a to fuel pump and battery (+) positive.
- Operate remote control.

If fuel pump runs:
- Check activation of fuel pump relay referring to wiring diagram Electrical Wiring Diagrams, Troubleshooting Component Locations.

If fuel pump does not run:
- Disconnect 4-pin connector from flange on fuel delivery unit.







- Connect diode test lamp V.A.G 1527 B to outer contacts of connector with auxiliary cables from V.A.G 1594 A.
- Operate remote control.
- LED must light up

If LED does not light up:
- Locate and eliminate open circuit referring to wiring diagram Electrical Wiring Diagrams, Troubleshooting Component Locations.

If LED lights up (voltage supply OK):







Unscrew nut with ring nut spanner 3217.
- Check that electrical wires between flange and fuel pump are connected.

If no open circuit can be found:
- Fuel pump is faulty. Replace fuel delivery unit.

Checking delivery rate

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

Work sequence
- Remove filler cap from fuel tank filler neck.

CAUTION: Fuel system is under pressure. Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.







- Pull off supply line -3- and collect leaking fuel with a cloth.

NOTE: Press locking ring inward to release fuel lines.







- Connect pressure gauge V.A.G 1318 to fuel supply line with adapters V.A.G 1318/17 and V.A.G 1318/23.
- Connect hose adapter V.A.G 1318/16 to adapter V.A.G 1318/11 of pressure gauge and hold it into a measuring container.
- Open shut-off tap on pressure gauge. Lever then points in through-flow direction -A -.
- Operate remote control V.A.G 1348/3A. At same time slowly close shut-off tap until pressure gauge shows 3 bar. From this point on do not move position of shut-off tap.
- Drain measuring container.
- The fuel pump delivery rate is dependent upon battery voltage. Therefore connect multimeter to vehicle battery using adapter cables from V.A.G 1594.
- Operate remote control for 30 seconds and measure battery voltage







- Compare quantity of fuel delivered with specification.
- *Minimum delivery cm.cu/30 seconds
- **Voltage at fuel pump with engine at rest 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, this will equate to a minimum delivery of 200 cu.cm/30 seconds.

If the minimum delivery rate is not attained:
- Check fuel lines for possible restrictions (kinks) or blockages.







- Pull supply hose -1- off inlet to fuel filter.

NOTE: Press locking ring inward to release fuel line.

- Connect pressure gauge V.A.G 1318 to hose with adapter V.A.G 1318/17.
- 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 filter strainer for soiling.

Only when up to now no fault has been detected:
- Fuel pump is faulty. Replace fuel delivery unit.

If delivery quantity has been attained, but nevertheless a fuel supply system fault (e.g. intermittent failure of fuel supply system) is suspected:
- Check current draw of fuel pump as follows:
- Reconnect all disconnected fuel lines.
- Disconnect 4-pin connector from flange on fuel delivery unit.







- Set multimeter to measuring range 20 A and make a series connection between connector contacts -1- and fuel pump using adapter cables from V.A.G 1594 A.

NOTE: It can also be connected to the current clamp of the multimeter V.A.G 1715 or the Vehicle diagnosis, Testing and Information system VAS 5051 to the adapter cables between the contacts -1- of the connector and the fuel pump.

- Connect contacts -4- of connector and fuel pump using adapter cables from V.A.G 1594 A.
- 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, the check can be performed during a road test, but a 2nd person is necessary.

If current consumption is exceeded:
- Fuel pump is faulty. Replace fuel delivery unit.

Checking fuel pump non-return valve

Requirements
- Remote control V.A.G 1348/3A is still connected.
- Pressure gauge V.A.G 1318 is still connected.

Work 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 shut-off tap (lever at right angles to through-flow direction - position -).
- Operate remote control at short intervals until a pressure of approx. 3 bar has built up.

CAUTION: 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, 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 is faulty. Replace fuel delivery unit.