Checking fuel delivery

Special tools, testers and auxiliary items required 

• Hand held remote control (jumper).
• Multimeter.
• Electrical connector test lead set.
• Fuel pressure test set (high pressure).

• 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.

Procedure 

• Remove fuel filler cap from fuel filler tube.
• Remove the rear seat bench, 72 - SEAT - FRAMES .

Fig 1: Identifying Cover With Fuel Pump Control Module J538

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• Remove the cover - 1  - with Fuel Pump (FP) Control Module J538 - 2  - from the fuel pump.
• Connect a Hand held remote control (jumper) to terminal - 1  - of the fuel delivery unit and to vehicle battery (+).

Fig 2: A Jumper Cable From A Electrical Connector Test Lead Set Connected To Terminal Of The Fuel Delivery Unit And To Vehicle Ground

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• Connect a jumper cable from a Electrical connector test lead set to terminal - 5  - of the fuel delivery unit and to vehicle Ground (GND).

Fig 3: Identifying Fuel Supply Line

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• Disconnect the fuel supply line - 2  - and catch escaping fuel using a rag.

Fig 4: High Pressure Fuel Gauge Connected Between The Fuel Filter And The Fuel Supply Line

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

Fig 5: Fuel Line From The High Pressure Fuel Gauge Connected To The Disconnected Fuel Return Line

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

• Close the shut-off valve of High pressure fuel 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 6: Fuel Quantity Graph

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• 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:

Fig 7: Connecting Pressure Gauge VAG 1318 With Adapters

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• Disconnect the supply hose - 1  - from the fuel filter input.
• Connect a High pressure fuel 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. For all fuel supply system removal/installation procedures and torque specifications. Refer to 20 FUEL SUPPLY .

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. For all fuel supply system removal/installation procedures and torque specifications. Refer to 20 FUEL SUPPLY .

Final procedures 

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

1. Check the DTC memory. Refer to.
2. If necessary, erase the DTC memory. Refer to.
3. If the DTC memory was erased, generate readiness code. Refer to.

End of procedure