With Manufacturer's Scan Tool

Fuel pump, checking









Special tools and equipment
- 3217 Ring nut wrench
- VAG 1348/3A Remote control with VAG 1348/3 2 adapter cable
- VAG 1466 Test system
- VAG 1527 B LED test light
- VAG 1594 A Adapter set
- VAG 1715 Multimeter
- VAG 1318 Pressure tester
- VAG 1318/1 Adapter
- VAG 1318/11 Adapter
- VAG 1318/17 Adapter
- VAG 1318/23 Adapter
- VAG 1332 Torque wrench (40-200 Nm)
- Measuring container
- Wiring diagram

Test conditions
- Battery voltage at least 11.5 V






- Fuse No. 28 OK
- 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, Refer to Inertia Fuel Shutoff Switch, Description and Operation

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 VAG 1 348/3A with adapter cable VAG 1348/3 2 to terminal 28a to fuel pump and battery positive (+).
- Operate remote control.

Fuel pump runs:
- Check activation of fuel pump relay using wiring diagram:

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






- Connect LED test light VAG 1527 B with auxiliary cables from VAG 1594 A to outer terminals 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 3217 wrench.
- 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

Test conditions
- Voltage supply OK
- Remote control VAG 1 348/3A 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 pipe/hose -1- and collect leaking fuel with a cloth.






- Connect pressure gauge VAG 1318 with adapter 1318/23 and VAG 1318/17 to fuel supply hose.
- Push hose VAG 13 1 8/1 onto adapter VAG 1318/1 1 on pressure gauge and hold hose in a measuring container.
- Open pressure gauge cut-off tap. Lever then points in through flow direction -A-.
- Operate remote control VAG 1 348/3A 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.
- Fuel pump delivery range is dependent upon battery voltage. Therefore, connect multimeter with adapter cables from VAG 1 594A 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 (approximately 2 volts less than battery voltage).
Example:
During the test a voltage of 12.5 volts is measured at the battery. As the voltage at the pump is approximately 2 volts less than the battery voltage then this will equate to a minimum delivery of 200 cm3/30 s.

If the minimum delivery rate is not attained:

- Check fuel pipes for possible restrictions (kinks) or blockages.






- Pull supply hose off fuel filter inlet.
- Connect pressure gauge VAG 1318 with adapter 1318 /17 to fuel supply hose.
- 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 soiling.

Only when up to now no malfunction has been detected:
- Fuel pump malfunctioning, replace fuel delivery unit.
- Check DTC memory:
- Read readiness code:

If the DTC memory has been erased or the Engine Control Module separated from the permanent (battery) positive, the readiness code must be generated again.
If the delivery rate has been attained but nevertheless a fuel supply system malfunction is suspected (e.g. intermittent failure of fuel supply system), check the current draw of the fuel pump as follows:
- Reconnect all disconnected fuel hoses.






- Connect multimeter VAG 1715 to wire -arrow- for terminal 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, to do this a 2nd person is necessary.

Observe the valid safety precautions when performing a road test.

If the current draw is exceeded:
- Fuel pump malfunctioning, replace fuel delivery unit.
- Check DTC memory:
- Read readiness code:

If the DTC memory has been erased or the Engine Control Module separated from the permanent (battery) positive, the readiness code must be generated again.

Checking fuel pump non-return valve

Test conditions
- Remote control VAG 1 348/3A is still connected
- Pressure gauge VAG 1318 is still connected

Test sequence

Note: With this check the fuel supply pipe 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 cut-off tap (lever at right angles to through flow direction - position -B-).
- Separate remote control at short intervals, until a pressure of approximately 3 bar has built up.

WARNING: Danger of spray when opening the cut-off tap, hold container over the pressure gauge free connection.

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

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

If no wiring malfunction is detected:
- Fuel pump malfunctioning, replace fuel delivery unit.
- Check DTC memory:
- Read readiness code:

If the DTC memory has been erased or the Engine Control Module separated from the permanent positive, the readiness code must be generated again.