Using electrical tools VW 1318 or similar pressure gauge 17 bar), connect the sensor to the system in a convenient place to measure the pressure in the fuel line. This can be done either in the fuel supply pipe or before the pressure regulator. If a special tool is used, set the lever so that the valve is open.
Disconnect the vacuum tube from the pressure regulator.
Remove the fuel pump relay from the main relay board and connect the long wire to terminal 52. If special tool US 4480/3 or equivalent is available, connect it in place of the fuel pump relay with the switch off
Apply 12V to the connected wire or turn the special tool switch to turn on the fuel pump. The pressure should be 3.8-4.2 bar. If the pressure is low, check the amount of fuel supplied by the pump.
If fuel exits the regulator at the vacuum hose connection, replace the regulator.
Install the fuel pump relay and start the engine. With the engine running at idle, when it warms up to operating temperature, connect a vacuum hose to the pressure regulator. The pressure should drop by about 0.6 bar. If this does not happen, check if the return tube is blocked, if there is no vacuum in the pressure regulator, or if the regulator is in good condition.
Measuring the amount of fuel supplied
Remove the fuel pump relay from the main relay board and connect the long wire to terminal 52. If tool US 4 480/3 or equivalent is present. connect it instead of the pump relay with the switch off.
Remove the fuel pump cover on the boot floor. On some models it is necessary to lift and securely support the vehicle to gain access to the pump. On the fuel pump plug, pull off the rubber cap to expose the leads, leaving the plug connected to the pump.
Using a voltmeter, connect the wires to the terminals and apply 12V to the wire, or turn the switch on the special tool to the on position to start the pump.
Check and record the voltage value with the pump running. It must be at least 9V. Switch off the pump.
In the engine compartment, disconnect the fuel return pipe connection and place them in a large container. On 4-cylinder and 10-valve 5-cylinder engines, turn on the fuel pump for 3 seconds and measure the amount of fuel collected in the container. Depending on the voltage at the pump, the amount of fuel should be approximately:
- 9 V - 335 cm3.
- 1B - 45cm3.
- 11 V - 60cm3.
- 12 V - 76cm3.
On turbocharged and 5-cylinder 2-valve engines, turn on the pump for 15 seconds. Depending on the voltage at the pump, the amount of fuel supplied should be approximately:
- 8 V - 295 cm3.
- 9 V - 355 cm3.
- 1B - 48cm3.
- 11 In- 56cm3.
- 12 V - 66cm3.
- 13 V - 75cm3.
- 14 V - 835 cm3.
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