First check that the connector -arrow- is fitted securely by pulling the connector without pressing the catch. The connector can cause a fault if it has not been fitted correctly.
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Now pull off connector.
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Check the contacts on the connector and on the fuel delivery unit for damage.
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Connect test instrument adapter/DSO (5-pin) -VAS 5565- to connector and fuel pump unit.
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Connect remote control -V.A.G 1348/3A- to test instrument adapter/DSO (5-pin) -VAS 5565- and to battery positive (+).
Note
t
This step serves only to have the fuel pump running when the engine is stopped.
t
The delivery rate of fuel pump is measured at 4 bar. Therefore, test fuel pressure before measuring fuel delivery rate → Chapter.
WARNING
Fuel supply line is pressurised. Wear eye protection and protective clothing to avoid possible injury and skin contact. Before loosening hose connections, wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
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Pull off return line -1- from fuel pressure regulator.
Note
Press in securing ring to release fuel line.
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Connect adapter set -VAS 6550/1- to fuel pressure regulator and hold end of adapter in measuring container.
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Operate remote control -V.A.G 1348/3A- for about 5 seconds to fill fuel filter.
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Empty measuring container.
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The quantity of fuel delivered by the fuel pump depends on the system voltage. Therefore, also connect multimeter -V.A.G 1715- to contacts -1 and 5- of 5-pin test instrument/DSO adapter -VAS 5565-.
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Operate remote control for 30 seconds while measuring battery voltage.
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Compare quantity of fuel delivered with specification.
*) Minimum delivery rate cm3/30 seconds
**) Voltage at fuel pump with engine not running and pump running.
Example:
During the test a voltage of 10.5 volts is measured. This equates to a minimum delivery rate of approx. 580cm3/30 sec.
If the specification is not attained:
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Check fuel pipes for possible restrictions (kinks) or blockages.
If fuel line is OK
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Remove cap from fuel filler neck and repeat check. If fuel delivery rate is now reached, check fuel tank breather.
If the specifications are still not attained:
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Check fuel filter (proceed as follows):
WARNING
Fuel supply line is pressurised. Wear eye protection and protective clothing to avoid possible injury and skin contact. Before loosening hose connections, wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
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Pull fuel supply line -arrow- off fuel filter.
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Connect pressure tester -VAS 6550- to fuel supply line with adapter -VAS 6550/1-. Hold adapter -VAS 6550/2- in a measuring container.
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Make sure that drain tap is closed and cut-off taps are open.
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Operate remote control -V.A.G 1348/3A-. Then slowly close shut-off tap -A- until a pressure of 4 bar is displayed on pressure gauge. From this point on do not move position of shut-off tap.
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Drain measuring container.
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Repeat delivery rate check.
If the minimum delivery rate is now attained:
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Renew fuel filter.
If the minimum delivery rate is again not attained
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Remove fuel delivery unit and check filter strainer for soiling.