With Manufacturer's Scan Tool

Fuel Pump, Checking

Special tools and equipment







- 3217 Union nut spanner
- V.A.G 1318 Pressure tester
- V.A.G 1318/1 Adapter
- V.A.G 1318/11 Adapter
- V.A.G 1318/17 Adapter
- V.A.G 1318/23 Adapter







- V.A.G 1332 Torque wrench (40 to 200 Nm)
- V.A.G 1348 Fuel quantity comparison meter
- V.A.G 1466 Test system VAG 1527B voltage tester
- V.A.G 1594 A Adapter set
- V.A.G 1715 Multimeter
- Measuring container
- Wiring diagram

Check conditions







- Fuse No. 28 OK.
- 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 an air conditioner, this must be switched off.

NOTE: Observe description of function of crash fuel shut-off.

Checking function and voltage supply

NOTE: Check whether a coded radio is installed as during the forthcoming work sequences the battery Ground strap must be disconnected. Obtain radio code first if necessary.

- Remove cover from fuel delivery unit.
- 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 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.

Fuel pump runs:
- Check activation of fuel pump relay using wiring diagram and V.A.G 1466 A.

Fuel pump does not run:
- Pull 4 pin connector off flange on fuel delivery unit.







- Connect VAG 1527B voltage tester with auxiliary cables from V.A.G 1594 A 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.):







- 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 malfunctioning, replace fuel delivery unit.

Checking delivery rate

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

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

WARNING: 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/hose -1- and collect leaking fuel with a cloth.







- Connect pressure gauge V.A.G 1318 with adapter 1318/23 and V.A.G 1318/17 to fuel supply line.
- Push hose V.A.G 1318/1 onto adapter V.A.G 1318/11 on pressure gauge and hold hose in a measuring container.
- Open pressure gauge shut-off tap. Lever then points in flow direction -A-.
- Operate remote control V.A.G 1348/3A and slowly close cut-off tap, until pressure gauge shows 3 bar. From this point on do not move position of cut-off tap.
- Empty measuring container.
- Quantity of fuel delivered by fuel pump is dependent upon battery voltage. Therefore connect the multimeter with adapter cables from V.A.G 1594 A to vehicle battery.
- Operate remote control for 30 seconds and measure battery voltage.







- Compare quantity of fuel delivered with specifications
- *)Minimum delivery cu.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 12.5 voltsis 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 200 cu.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 V.A.G 1318 with adapter 1318/17 to fuel supply line.
- 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 filter for dirt.
- Only when up to now no malfunction has been detected:
- Fuel pump malfunctioning, replace fuel delivery unit.
- Check DTC memory.
- Read readiness code.
- Generate readiness code again if DTC memory has been erased or engine control module separated from permanent positive.

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 fuel pump as follows:
- Reconnect all disconnected fuel lines.







- Connect multimeter V.A.G 1715 to wire -arrow- for contact 1 of 4-pin connector using 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, you can perform the check during a test drive with the help of a 2nd person.

If the current draw is exceeded:
- Fuel pump malfunctioning, replace fuel delivery unit.
- Check DTC memory.
- Read readiness code.
- Generate readiness code again if DTC memory has been erased or engine control module separated from permanent positive.

Checking fuel pump non-return valve

Test conditions

- Remote control V.A.G 1348/3A is still connected.
- Pressure gauge V.A.G 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 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 throughflow direction - position -B-).
- Separate remote control at short intervals, until a pressure of approx. 3 bar has built up.

WARNING: Danger of spray when opening the shut-offtap, hold container over the pressure gauge free connection.

- If pressure builds up too high, lower excess pressure by carefully opening the shut-off tap.
- Watch pressure drop on gauge. After 10 minutes the pressure must not drop below 2.5 bar.

If the pressure drops further:
- Check pipe connections for leaks.

If no malfunction is detected in the wiring:
- Fuel pump malfunctioning, replace fuel delivery unit.
- Check DTC memory.
- Read readiness code.
- Generate readiness code again if DTC memory has been erased or engine control module separated from the permanent positive.