Fuel Pump, Checking

Fuel Pump, Checking







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 1348/32

Special tools, testers and auxiliary items required







- Adapter V.A.G 1318/1







- Connector Test Set V.A.G 1594 A







- Multimeter V.A.G 1715

Test conditions







- Fuse no. 28 must be OK.
- Battery voltage must be at least 11.5 Volts.
- All electrical consumers like, for example, 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 crash fuel shut off function.

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

CAUTION: Fuel supply line is under pressure. Wear eye protection and protective clothing in order to avoid injuries by 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. Torque specification: 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 1318/1 onto Adapter V.A.G 1318/11 of Pressure Gauge V.A.G 1318 and hold it in a measuring container.
- Open shutoff valve of Pressure Gauge V.A.G 1318. The lever then points in the direction of flow - A -.
- Remove cover in front of fuse holder.







- Pull fuse No. 28 from the fuse holder.
- Connect Remote Control V.A.G 1348/3A with Adapter Cable V.A.G 1348/32 to contact 28a to fuel pump and battery positive (+).
- Operate Remote Control V.A.G 1348/3A. Slowly close shutoff tap, until Pressure Gauge shows 3 bar. From this point on do not move position of shutoff tap.
- Empty the 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 Kit V.A.G 1594 A.
- Operate Remote Control for 30 seconds and measure battery voltage.







- Compare the 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 the 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 the fuel filter.

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

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

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







- Connect Multimeter V.A.G 1715 to wire of 4-pin connector terminal 1 - arrow - using current pick-up.
- Start the 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

Test conditions
- Remote Control V.A.G 1348/3A connected
- Pressure Gauge V.A.G 1318 connected to fuel supply line of fuel supply tube

Test sequence

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







- Close Pressure Gauge shutoff valve (lever perpendicular to direction of flow position - B -).
- Operate Remote Control at short intervals, until a pressure of approx. 3 bar has built up.

CAUTION: Danger of fuel spray when opening shutoff tap; Wear protective eyewear and clothing to prevent injuries and skin contact with fuel. Hold a container in front of the open connection of the Pressure Gauge.

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

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.