Fuel Pump, Checking

Fuel Pump, Checking

Special tools and equipment
- 3217 ring nut spanner
- VAG1318 pressure gauge
- VAG1318/1 adapter
- VAG 1318/11 adapter
- VAG1318/17 adapter
- VAG 1318/23 adapter












- VAG1332 torque wrench (40 to 200 Nm)
- VAG1348 quantity comparison tool
- VAG1466 electrical circuit tester
- VAG1527B voltage tester
- VAG1594A connector test kit
- VAG1715 multimeter
- Measuring container
- Wiring diagram

Test requirements
- Battery voltage at least 11.5 V

Checking function and voltage supply
- Remove cover from Fuel Pump (FP):
- Loosen carpet and lift over parking brake lever.
- Unbolt parking brake lever and remove fuel pump cover.
- Operate starter briefly. Fuel pump must audibly start up.
- Switch off ignition.

If Fuel Pump (FP) does not start up:
- Pull off cover in front of relay carrier.







- Remove fuel pump relay from relay carrier (relay position 12).
- Connect VAG1348/3A remote control to terminal 4 and B + using VAG1348/3-2 remote control connection.
- Operate remote control.

If Fuel Pump (FP) runs:
- Use VAG1466A to check activation of the Fuel Pump (FP) relay according to wiring diagram:

If Fuel Pump (FP) does not run:







- Disconnect 4-pin connector from flange at fuel tank.







- Connect VAG1527B voltage tester to outer terminals of connector using adapter cables from VAG1594A connector test kit.
- Operate remote control. LED must light up.

LED does not light up:
- Locate and repair open circuit using wiring diagram:

LED lights up (voltage supply OK):
- Disconnect supply and return line from flange.







- Use ring nut spanner 3217 to remove union nut.
- Check whether electrical wires between flange and Fuel Pump (FP) are connected.

If there are no open circuits:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP).

Checking fuel delivery
- Voltage supply OK
- VAG1348/3A remote control connected

Test sequence
- Remove fuel filler cap from fuel delivery unit.


WARNING!
Fuel supply line is underpressure! Before loosening hose connections, place rags around the connection point. Then release pressure by carefully pulling on hose.







- Disconnect supply line -2- (with white marking) and catch escaping fuel using a rag.


NOTE: Depress buttons on hose connections to do so.







- Connect pressure gauge VAG1318 to fuel supply line using adapters VAG1318/23 and VAG1318/17.
- Connect VAG1318/1 pressure gauge adapter to VAG1318/11 adapter of pressure gauge and hold into measuring container.
- Open shut-off valve of pressure gauge. Lever will point in direction of flow -A-.
- Operate VAG1348/3A remote control. Slowly close shut-off valve until pressure gauge displays 3 bar is indicated. Do not change position of shut-off valve any more.
- Empty measuring container.
- Delivery rate of Fuel Pump (FP) is dependant on battery voltage. Therefore, connect multimeter to vehicle battery using adapter cables from VAG1594A connector test kit.
- Operate remote control 30 seconds long and measure battery voltage.







- Compare fuel quantity pumped with specified value.
*) Minimum delivery rate cubic cm/30 s
**) Voltage at fuel pump with engine off and pump running (approx. 2 volts less than battery voltage).

Read-out example:
During test, a voltage of 12.2 volts is measured at battery. Since the voltage at the pump is approx. 2 volts less than battery voltage, there is a minimum delivery rate of 550 cubic cm/30 s.

If minimum delivery rate is not obtained:
- Check fuel lines for kinks or clogging.







- Disconnect supply line -1- from fuel filter input.
- Connect VAG1318 pressure gauge with 1318/17 adapter to hose.
- Repeat test of delivery rate.

If minimum delivery rate is obtained now:
- Replace fuel filter.

If minimum delivery rate is still not obtained:
- Remove Fuel Pump (FP) and check filter strainer for dirt.

Only if no malfunctions have been found yet:
- Replace Fuel Pump (FP).

Delivery rate has been obtained, but malfunctions are still suspected in the fuel supply (e.g. sporadic loss of fuel supply):
- Check Fuel Pump (FP) current draw as follows:
- Re-connect all disconnected fuel lines.







- Connect VAG 1715 multimeter with electrical current probe to blue/red wire of wiring harness.
- Start engine and let run at idle.
- Measure Fuel Pump (FP) current draw.
Specification: max: 8 amperes


NOTE: If disturbance in fuel system is sporadic, test can also be performed during a road test, but a 2nd person is required.


If current draw is exceeded:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP).

Check Fuel Pump (FP) check-valve.

Test requirements
- VAG1348/3A remote control is still connected.
- VAG1318 pressure gauge is still connected.

Test sequence


NOTE: This test also checks the connections of the fuel supply line from Fuel Pump (FP) to connection point of VAG1318 pressure gauge for proper seal.







- Close pressure gauge shut-off valve (lever perpendicular to direction of flow -position B-).
- Operate remote control in short intervals until a positive pressure of approx. 3 bar has built up.


WARNING!
Danger of spray when opening shut-off valve. Hold container in front of open connection on pressure gauge.


- If excess pressure is built up, reduce pressure by carefully opening shut-off valve.
- Observe pressure drop on pressure gauge. Pressure must not fall below 2.5 bar within 10 minutes.

If pressure drops further:
- Check line connections for proper seal.

If no malfunctions are found in wires:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP).