Test sequence

Remove filler cap from fuel tank filler neck.

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

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Disconnect supply hose - 3 - (with white marking) and collect fuel that may leak out with a cloth.

NOTE:

Press buttons on hose couplings to do so.

CAUTION: Fuel supply lines are under pressure! Before removing from hose connections wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.

Fig 2: Connecting VAG 1318 Components To Fuel Supply Line

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Connect pressure gauge VAG 1318 to fuel supply pipe using adapter VAG 1318/23 and adapter VAG 1318/17.
Push hose adapter VAG 1318/16 onto adapter VAG 1318/11 on pressure gauge and hold hose in a measuring container.
Open shut-off tap on pressure gauge. Lever then points in flow direction - A -.
Operate remote control VAG 1348/3A. Close shut-off tap slowly, until pressure gauge shows 3 bar. From now on do not alter setting of shut-off tap.

Empty measuring container.

The quantity of fuel delivered by the fuel pump depends on the battery voltage.

Connect multimeter to vehicle battery using adapter cables VAG 1594 A.
Operate remote control for 30 seconds and measure battery voltage.

Fig 3: Fuel Delivery Rate Graph

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Compare quantity of fuel delivered with nominal value.

* Minimum delivery cm ³ /30 seconds

* Voltage at fuel pump with engine not running 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, the result is a minimum delivery of 200 cm ³ /30 seconds.

If the minimum delivery rate is not attained:

Check fuel pipes for possible restrictions (kinks) or blockages.

Fig 4: Connecting Pressure Gauge VAG 1318 To Hose With Adapter VAG 1318/17 To Fuel Filter

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Disconnect fuel line - 1 - from input side of fuel filter.

NOTE:

Press buttons on hose couplings to disconnect.

Connect pressure gauge VAG 1318 to hose using adapter 1318/17.
Repeat delivery rate test.

If the minimum delivery rate is now attained:

Replace fuel filter.

If the minimum delivery rate is again not attained:

Remove fuel delivery unit and check strainer filter for soiling.

Only if no faults have been detected up to now:

Fuel pump faulty, replace fuel delivery unit → Fuel delivery unit , removing and installing , Removing and installing fuel delivery unit.

If the delivery rate has been attained but a fuel supply system fault is still suspected (e.g. intermittent failure of fuel supply system):

Check current draw of fuel pump as follows:
Reconnect all disconnected fuel lines.

Fig 5: Measuring Current Draw Of Fuel Pump Using VAG 1715

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Connect multimeter VAG 1715 to wire - arrow - for contact 1of 4-pin connector using current pick-up clamp.
Start engine and run at idling speed.
Measure current draw of fuel pump. Specification: max. 8 amps.

NOTE:

If the fuel system malfunction is intermittent, perform the check during a test drive with the assistance of a 2nd person.

If the current draw is exceeded:

Fuel pump faulty, replace fuel delivery unit → Fuel delivery unit , removing and installing , Removing and installing fuel delivery unit.