Fuel Pump Pressure, Checking

Special tools and workshop equipment required 

• Multimeter.
• fuel line adapter set V.A.G. 1318/17A. These tools may be substituted with an equivalent aftermarket tool and are also available for rental or purchase through the local dealer.
• In line Fuel pressure gauge with shutoff. (high pressure).

Test conditions 

• Battery voltage 12.5 V
• Function and voltage supply for the Fuel Pump is OK.
• Fuel tank at least ¹ /₄ filled.
• Ignition switched OFF.

Test procedure 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK 

Start diagnosis 

-- Disconnect fuel supply line and catch any fuel coming out with a shop towel. Refer to the Repair information for location.

-- Install a fuel pressure gauge with appropriate adapters.

-- Open shut off valve on fuel gauge.

-- Switch ignition on and off repeatedly until fuel pressure stops increasing pressure.

-- Read fuel pressure on the gauge.

• Specified value: 3.5 to 4.3 bar
• Turn the ignition switch OFF.

If specification is exceeded:

-- Check return line between fuel filter and fuel pump for kinks or blockage.

If no malfunction in fuel return line is found:

-- Pressure relief valve in fuel filter is malfunctioning.

-- Replace the fuel filter. Refer to the Repair information.

If specified value was Not obtained:

-- Check fuel pressure at the fuel filter between fuel pump and fuel filter using appropriate adapters

-- Open shut off valve on gauge and start the engine. Allow to idle.

-- Slowly close the pressure gauge shut off and note the fuel pressure.

• Pressure must increase to 4 bar.

When 4 bar is reached: Open shut off tap immediately!

Turn the ignition switch OFF.

If pressure has increased during test:

-- Fuel pump is OK. Pressure relief valve in fuel filter is malfunctioning.

-- Replace the fuel filter. Refer to the Repair information.

If pressure did not increase:

-- Fuel pump is faulty

-- Replace the fuel pump. Refer to the Repair information.

Final procedures 

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

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .