FWD

Fuel Pump, Checking

Checking fuel delivery
Checking fuel pump non-return valve







Special tools, testers and auxiliary items required
- Pressure gauge V.A.G 1318
- Adapter V.A.G 1318/10
- Adapter V.A.G 1318/11
- Adapter V.A.G 1318/12
- Adapter V.A.G 1318/16
- Remote control V.A.G 1348/3A with adapter cable V.A.G 1348/3-2

Special tools, testers and auxiliary items required







- Connector test set V.A.G 1594C







- Multimeter V.A.G1715

Conditions







- Fuse no. 28 must be OK.
- Battery voltage must be at least 11.5 Volts.
- All electrical consumers, e.g. lights and rear window heating, must be switched off.
- If vehicle is equipped with an A/C system, it must be switched off.

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

Checking delivery rate
- Remove fuel filler cap from fuel filler tube.
- Remove intake manifold cover.

CAUTION: Fuel supply lines are under pressure. Wear eye protection and protective gloves to avoid injuries and skin contact with fuel. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.







- Open threaded connection - arrow - and catch exiting fuel using a rag.

NOTE: Counterhold hex bolt of fuel distributor to release bolt. Tightening torque: 22 Nm.







- Connect pressure gauge V.A.G 1318 with adapter V.A.G 1318/12 to fuel supply line.
- Connect hose V.A.G 1318/16 onto adapter V.A.G 1318/11 of pressure gauge V.A.G 1318 and hold it in a measuring container.
- Open shut-off valve of pressure gauge V.A.G 1318. Lever will point in direction of flow - A -.
- Remove cover in front of fuse holder.







- Pull fuse No. 28 from 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 V.A.G 1348/3A. Slowly close shut-off tap, until pressure gauge shows 4 bar. From this point on do not move position of shut-off tap.
- Empty measuring container.
- Delivery rate of Fuel Pump (FP) is dependent on battery voltage. Therefore, connect multimeter to vehicle battery using adapter cables from connector test set V.A.G 1594 A.
- Operate remote control for 30 seconds and measure battery voltage.







- Compare quantity of fuel delivered with specification.
- *)Minimum delivery rate cubic cm/30 s
- **)Voltage at fuel pump with engine off 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 then 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- from inlet to fuel filter.
- Connect pressure gauge V.A.G 1318 with adapter V.A.G 1318/10 to 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 fuel strainer for soiling.

Only when up to now no malfunction has been detected:
- Fuel Pump (FP) faulty, replace fuel delivery unit.

If the delivery rate has been obtained, but malfunctions are still suspected in the fuel supply, for example, sporadic loss of fuel supply:
- Check current draw of fuel pump as follows:
- Reconnect all disconnected fuel lines.
- Remove luggage compartment floor cover.
- Remove cover from Fuel Pump (FP).







- Connect current probe of multimeter V.A.G 1715 or vehicle diagnostic, testing, and information system VAS 5051 to wire of 4-pin connector, terminal 1. arrow -.
- Start engine and run at idle speed.
- Measure current draw of fuel pump.
- Specification: max. 8 amps.

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

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

Fuel Pump (FP) check valve, checking

Conditions
- Remote control V.A.G 1348/3A connected
- Pressure gauge V.A.G 1318 connected to fuel supply line of fuel supply tube

Work sequence

NOTE: This test also checks the connections of the fuel supply line from the fuel delivery unit to connection point of pressure gauge V.A.G 1318 for proper seal.







- Close pressure gauge shut-off valve (lever perpendicular to direction of flow, position - B -).
- Operate remote control at short intervals, until a pressure of approx. 4 bar has built up.

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

- If pressure builds up too high, lower excess pressure by carefully opening shut-off tap.
- Watch pressure drop on gauge.
- After 10 minutes the pressure must not drop below
- Engine cold: 2.2 bar Engine hot: 3.0 bar

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

If no fault is detected in the wiring:
- Fuel Pump (FP) faulty, replace fuel delivery unit.