Volkswagen Workshop Service and Repair Manuals

Checking fuel system pressurisation pump delivery rate Special tools and workshop equipment required t  Vehicle diagnosis tester t  Hose adapter -VAS 6551/5-2- t  Hose adapter -VAS 6551/5-3- t  Adapter -VAS 6551/5-1-

Hose adapter set -VAS 6551/5-

Pressure gauge -VAS 6551-

Test instrument adapter/DSO (5-pin) -VAS 5565-

Hand-held multimeter -V.A.G 1526D- Test sequence: l  Delivery pressure of fuel pump (fuel low pressure) has been checked previously → Chapter l  Fuel tank at least 3/4 full. l  Connect charger or battery voltage above 12.5 volts »Carry out the following work sequence.«   WARNING t  Always read rules for cleanliness and instructions for working on fuel system → Chapter. t  Always follow these rules for cleanliness and instructions before starting work and while working on the fuel system. t  Wrap a clean cloth around the connection before opening the fuel system, then carefully loosen the connection to release the pressure.

–  Pull fuel supply line (black or black marking) -3- off fuel delivery unit. –  Collect escaping fuel with a cleaning cloth.

–  Connect connection -A- of pressure tester -VAS 6551- with line -VAS 6551/1- to open end of fuel delivery unit.

–  From connection -B-, route hose adapter -VAS 6551/2- into a ≥ 3 litre measuring container -3- and hold there. –  Switch on pressure tester -VAS 6551- by pressing On/Off button. –  Open shut-off taps „B“ + „C“ of pressure tester -VAS 6551-. –  Switch ignition on. –  Connect vehicle diagnosis tester and carry out guided function „Checking electronic fuel pump(s)“.   Note The fuel pump is now activated for 30 seconds. –  Carefully open shut-off tap -B- completely. –  Slowly close shut-off tap -B- while reading pressure displayed on pressure tester -VAS 6551-. Set specification of 5 ± 0.2  bar by closing the tap carefully. –  Drain measuring container. Repeat function „Checking electronic fuel pump(s)“ The amount of fuel delivered by the fuel pump depends on the voltage at the fuel delivery unit.

–  Therefore, also connect multimeter -V.A.G 1526- to outputs -1 and 5- of test instrument/DSO adapter 5-pin -VAS 5565-. Test prerequisites l  At RT = room temperature or a fuel temperature of T = (20 +- 5) °C . l  At a pressure of 5 ± 0.2  bar at flange output l  During the checking process, there must be voltages of 11 to 15 volts at the fuel pump. Measured at the flange connector of the delivery unit. –  Carry out in the guided function „Checking electronic fuel pump(s)“

–  Compare the amount of fuel delivered with the read value from the table. *) Delivered amount of fuel in ml/30 s **) Voltage at fuel delivery unit (V) with engine not running and pump running. Example: During the test, a voltage of 12.0 volts, for example, is measured at the fuel delivery unit. The delivered amount of fuel is therefore 1100 ml/30 s If the required amount of delivered fuel is achieved, or if more is measured: Fuel pump ok. If the amount of fuel to be delivered by the fuel pump is not achieved, the following faults have occurred: t  Battery voltage below 12.5 V (connect charger) t  Fuel delivery unit filter strainer soiled. Check filter strainer for soiling. t  Voltages in the range from 11 to 15 volts were not reached during the testing process. t  Checking voltage supply of fuel pump → Chapter t  Check current consumption of fuel pump → Chapter.