Skoda Workshop Service and Repair Manuals

Inspecting the fuel pump operating pressure Special tools and workshop equipment required t  Pressure gauge, e.g. -VAS 6551- t  Hose adapter, e.g. -VAS 6551/1- t  Hose adapter, e.g. -VAS 6551/2- t  Vehicle diagnosis, measurement and information system -VAS 505x- Test conditions l  Battery voltage at least 12 V. l  Fuses o.k. → Current flow diagrams, Electrical fault finding and Fitting locations. l  Fuel tank at least 3/4 full. l  Horizontal position of the vehicle. l  Flow path in the fuel hoses and the lines in the engine compartment and at the underbody not interrupted due to damage (kinks). l  All electrical consumers such as the lights and rear window heater must be switched off. Test sequence   Note t  Observe safety measures when working on the fuel system → Chapter. t  Observe rules for cleanliness → Chapter. –  Remove engine cover → Chapter. –  Collect the fuel which flows out with a cloth. –  Disconnect the push-fit coupling of the fuel feed line to the high pressure pump ( → Chapter, Pos. 3) at the fuel filter outlet.

–  Incorporate the pressure gauge -VAS 6551- with the lines -VAS 6551/1- and -VAS 6551/2- in the fuel circuit. –  Switch on the pressure gauge -VAS 6551- by pressing the button On/Off.

–  Open the shut-off cocks „A“ and „B“ of the pressure gauge -VAS 6551-, close the shut-off cock „C“. –  Connect vehicle diagnosis, measurement and information system -VAS 505x- and carry out the function „test fuel pump“.   Note The fuel pump is actuated for 30 seconds. –  Read the pressure on the pressure gauge: l  Specified value: min. 0.45 MPa (4.5 bar) –  Start engine and run in idle. –  Read the pressure on the pressure gauge: l  Specified value: min. 0.45 MPa (4.5 bar) –  Position the pressure gauge -VAS 6551- on the windscreen in such a way that it is legible from inside. –  Increase the idling speed to 2500 rpm. –  Read the pressure on the pressure gauge: l  Specified value: min. 0.45 MPa (4.5 bar) Repeat the test at the feed line to the fuel filter if the specified value is not reached. This will determine whether the fuel filter is not clogged. –  Re-connect the fuel feed line to the high pressure pump at the fuel filter outlet. –  Collect the fuel which flows out with a cloth. –  Disconnect the push-fit coupling of the fuel feed line ( → Chapter, Pos. 2) at the fuel filter inlet.

–  Connect the pressure gauge -VAS 6551- with the lines -VAS 6551/1- and -VAS 6551/2- to the open ends. –  The pressure measurement is carried out in the same way as the previous test. l  Now the pressure value must be at least 0.46 MPa (4.6 bar). If the prescribed pressure values are reached, the difference however of the measured pressure values upstream and downstream of the filter is 0.04 MPa (0.4 bar) or higher: –  Replace the fuel filter → Chapter. If the prescribed pressure value is not reached:

–  Check the additional fuel filter -4- at the fuel tank. To do so, carry out a measurement directly at the fuel delivery unit as described below: –  Re-connect fuel feed line at fuel filter inlet. Vehicles Fabia II –  Position right rear seat vertically → Body Work; Rep. gr.72. Vehicles Roomster –  Fold the rear seat forward and position the middle and rear seat vertically → Body Work; Rep. gr.72. Continued for all vehicles

–  Remove the cover of the fuel delivery unit under the mat.

–  First of all check the plug -arrow- for firm seating. Pull on the plug without pressing the locking mechanism. If the plug was not correctly plugged in, it may have caused a fault. –  Collect the fuel which flows out with a cloth.

–  Disconnect the fuel feed line -4- from the fuel delivery unit.

–  Connect the connection -A- of the pressure gauge -VAS 6551- with the line -VAS 6551/1- to the open nozzles of the fuel delivery unit. –  Close the shut-off cocks „B“ and „C“ of the pressure gauge -VAS 6551-. –  Switch on the pressure gauge -VAS 6551- by pressing the button On/Off. –  Connect vehicle diagnosis, measurement and information system -VAS 505x- and carry out the function „test fuel pump“.   Note The fuel pump is actuated for 30 seconds. –  Read the pressure on the pressure gauge: l  Specified value: 0.67 ... 0.77 MPa (6.7 ... 7.7 bar) If the specified pressure is reached:

–  Replace the additional fuel filter -4- with the integrated pressure regulator.   Note t  On this fuel system, the additional fuel filter only fulfills the function of a pressure regulator. t  The fuel is not filtered. t  Check fitting position. An incorrect installation can cause the following problems: t  Impermissible increase of fuel pressure. t  Lifetime reduction of the fuel delivery unit. t  Noises of the fuel delivery unit. If the specified pressure is not reached, the pressure is interrupted again, the following faults may have occurred: t  Battery voltage too low. t  Voltage supply of fuel pump not O.K., check → Chapter. t  Fuel flow rate of fuel pump too low, check → Chapter. t  Power consumption of fuel pump too low, check → Chapter. t  Filter strainer of fuel delivery unit soiled. Remove, in order to check the fuel delivery unit → Chapter. t  Quick coupling in the fuel delivery unit faulty. Remove, in order to check the fuel delivery unit → Chapter.