Fuel Pump: Testing and Inspection

Fuel Pump, Checking

Special tools and equipment







- VAG 1318 Pressure gauge
- VAG 1318/10 Adapter
- VAG 1318/11 Adapter
- VAG 1318/12 Adapter
- VAG 1348 Remote control
- VAG 1466 A Test system







- VAG 1527B voltage tester
- VAG 1594 Adapter set
- VAG 1715 Multimeter
- VAG 1332 Torque wrench (40 to 200 Nm)
- VAG 1318/1 Hose
- Measuring container
- Wiring diagram








- Ring nut spanner 3217

Checking conditions
- Battery voltage at least 11.5V







- Fuse No. 28 OK.

Checking function and voltage supply
- Remove floor cover.
- Briefly operate starter.
- Fuel pump must be heard to run.
- 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 1348/3A 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 See Instructions with tester VAG 1466

Fuel pump does not run:







- Pull 4-pin connector off fuel tank flange (arrow).







- Connect voltage tester VAG 1527B with auxiliary cables from VAG 1594 to outer contacts of connector.
- Operate remote control.

- LED must light up

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

If LED lights up (voltage supply OK):







- Remove union nut with spanner 3217.
- Check that wiring between flange and fuel pump is connected.

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

Checking fuel delivery rate

Checking conditions
- Voltage supply OK.
- Remote control VAG 1348/3A connected.

Checking sequence
- Remove 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 VAG 1318/1 onto adapter VAG 1318/11 on pressure gauge and hold hose in a measuring container.
- Open pressure gauge shut-off tap. Lever then points in direction of flow -A-.
- Operate remote control VAG 1348/3A and slowly close shut-off tap until pressure gauge shows 3 bar. From this point on do not move position of shut-off tap.
- Empty measuring container.
- Connect multimeter with adapter cables from VAG 1594 to vehicle battery (fuel pump delivery range is dependent upon battery voltage).
- Operate remote control for 30 seconds and measure battery voltage.







- Compare quantity of fuel delivered with specification.
*) Minimum delivery cubic.cm/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, this will equate to a minimum delivery of 550 cubic.cm/30 s.

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.
- 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 strainer for blockages.

Only if up to now no faulty components have been detected:

- Fuel pump is faulty, replace fuel delivery unit.

If the delivery rate has been attained but nevertheless you suspect a fuel supply system malfunction (e.g, intermittent failure of fuel supply system):

- Check current draw of the fuel pump as follows:
- Reconnect all disconnected fuel lines.
- Remove floor cover.







- Connect multimeter VAG 1715 with current clamp on green/yellow wire in wiring harness.
- Start engine and run at idling speed.
- Measure the current draw of the fuel pump.
- Specification: max. 8 amps.


NOTE: If the fuel system malfunction is intermittent, you can perform the check during a test drive with a 2nd person in the vehicle.


If the current draw is exceeded:
- Fuel pump is faulty, replace fuel delivery unit