Checking fuel delivery

WARNING: This page is about a different variant/trim than selected.

Special tools, testers and auxiliary items required

Hand held remote control (jumper).
Multimeter.
Electrical connector test lead set.
Fuel pressure test set.
Measuring container, fuel-resistant.

Test conditions

Battery voltage 12.5 V
Fuel filter OK
Fuel tank at least ¹ / ₄ filled.
Fuel pressure regulator OK.

Ignition switched off.

CAUTION: Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before loosening hose connections, place rags around the connection point. Then release pressure by carefully pulling on hose.

Procedure

Remove fuel filler cap from fuel filler tube.
Remove the rear seat bench. Refer to 72 - SEAT - FRAMES .
Connect a Hand held remote control (jumper) to terminal - 1 - of the fuel delivery unit and to vehicle battery (+).
Connect a jumper cable from a Electrical connector test lead set to terminal 4 of the fuel delivery unit and to vehicle Ground (GND).

Fig 1: Identifying Vacuum Hose To Throttle Valve Control Module, Fuel Return Hose & Fuel Supply Hose

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Disconnect the fuel supply line - 3 - and catch escaping fuel using a rag.

NOTE:

Press in securing ring to disengage the fuel lines.

Fig 2: High Pressure Fuel Gauge Connected Between The Fuel Filter And The Fuel Supply Line

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Connect a Fuel pressure gauge between the fuel filter and fuel supply line.

Fig 3: Connecting VAG 1318 Components To Fuel Supply Line

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Connect a fuel line from the Fuel pressure gauge to the disconnected fuel return line and hold it in the measuring container.

CAUTION: Danger of spraying when opening shut-off valve; wear protective goggles and protective clothing to prevent injuries and contact with skin. Hold container in front of open connection of pressure measuring device.

Close the shut-off valve of Fuel pressure gauge.
Press switch on the Hand held remote control (jumper) while opening the shut-off valve slowly until 4 bar positive pressure is indicated on pressure gauge. Do not change position of the shut-off valve.
Empty into the measuring container.

Delivery rate of the fuel pump is dependent on the battery voltage.

Operate the remote control for 30 seconds.
Using a Multimeter , check battery voltage while the fuel pump is running.

Fig 4: Fuel Delivery Rate Graph

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Compare the fuel quantity pumped with the specified value.

*) Minimum delivery rate cm ³ /30 s

**) Voltage at the fuel pump with the engine off and the fuel pump running (approx. 2 Volts less than battery voltage).

Read-out example:

During test, a voltage of 12.5 Volts is measured at battery. Since voltage at the pump is approx. 2 Volts less than battery voltage, there is a minimum delivery rate of approx. 580 cm ³ /30 s.

If the minimum delivery rate is not obtained:

Check fuel lines for restrictions (kinks) or clogging.

If no malfunction can be found:

Disconnect the supply hose from the fuel filter input.

Fig 5: High Pressure Fuel Gauge Connected Between The Fuel Filter And The Fuel Supply Line

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Connect a Fuel pressure gauge between the fuel filter and fuel supply line.
Repeat the delivery rate test.

If the minimum delivery rate is obtained:

Replace the fuel filter.

If the minimum delivery rate is not obtained:

Remove the fuel pump and check the strainer filter for dirt.

If no malfunctions have been found:

Replace the fuel pump. Refer to 20 - FUEL SUPPLY .

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

Check the DTC memory.
If necessary, erase the DTC memory.
If the DTC memory was erased, generate readiness code.

End diagnosis