Fuel Pump: Testing and Inspection
WM 206601 Checking delivery rate of electric fuel pump
Tools
Technical values
Preliminary work
Information
- The battery voltage must not fall below 12.5 volts during the fuel delivery rate check.
1. Check the battery charge state using a voltmeter or the PIWIS Tester 9718.
1.1. Connect a charger.
2. Remove underbody covers.
2.1. Remove rear cover.
-> 519419 Removing and installing cover for rear underbody.
2.2. Remove centre part of middle cover.
-> 519319 Removing and installing cover for centre underbody.
Checking
Checking delivery rate of electric fuel pump
Information
- The battery voltage must not fall below 12.5 volts during the fuel delivery rate check.
1. Attach or mount a warning sign in a clearly visible position on the vehicle.
Example of warning sign for naked flames
2. Reduce fuel pump supply pressure. This procedure does not cause an entry to be made in the fault memory.
2.1. To do this, remove the cover of the fuse carrier in the left footwell and take out the fuse for the fuel pump - level D, fuse F1 (1st from left) -.
2.2. Then start the engine. The engine runs for a short time and then stops.
2.3. Insert the fuse again and replace the cover.
3. PIWIS Tester 9718 must be connected to the adapter line at the input socket in the vehicle and ignition must be switched on.
3.1. Switch off all loads, such as radio, air conditioning, etc. Switch on the Tester and select the relevant vehicle.
4. Run the individual control unit search for DME. Select DME and press F12>> to start the control unit search.
Control unit search
5. Find and select the Special functions menu item. Press F12>> to continue.
Special functions menu item
6. Select Drain tank in the menu and press F12>> to continue.
Drain tank menu item
7. The following message is displayed.
Drain tank message
8. Have a measurement adapter 9705 , a fuel-resistant container, a measuring cup and a stopwatch to hand for measuring.
Measurement adapter 9705
9. Open the retaining clip -1- for the fuel lines on the underbody. To do this, unclip the locking lugs -arrow-.
Opening retaining clip on fuel lines
WARNING
Highly inflammable or explosive materials
- Danger of fire or explosion
-> Avoid contact with hot parts or sources of ignition.
-> Use suction to remove ignitable vapours.
-> Attach warning sign in a clearly visible position.
10. Disconnect rapid-action coupling on the fuel supply line -1- by pressing in the locking lug and pulling off the coupling. Collect emerging residual fuel with a cloth.
Rapid-action coupling on fuel pressure line
11. Connect the measuring adapter 9705 special tool to the fuel line using the rapid-action coupling. Make sure that the coupling is fitted correctly and securely (it must lock with an audible click).
11.1. Pull on the lines to check that they are secure.
Connecting the measurement adapter
12. Place the drainage hose after the pressure regulator into a petrol-resistant container. Make sure that the container does not tip over.
Example of tank
13. Have a stopwatch ready for the following measurement.
14. Start the Drain tank routine by pressing F8 Start and start the stopwatch at the same time.
Measuring time: 60 seconds!
14.1. Collect emerging fuel in a container you have to hand.
Starting the Drain tank routine
15. Press F8=Stop after 60 seconds to deactivate the routine.
Stopping the Drain tank routine
16. Pour the collected fuel into the measuring cup and compare the quantity with the vehicle-specific values listed below.
This gives the minimum pump rate.
16.1. Carrera 2:
=> Diameter: 2.80 l/min
16.2. Carrera 4:
=> Diameter: 2.75 l/min
17. Remove measurement adapter 9705 and attach rapid-action coupling to fuel supply line. Collect escaping fuel. Make sure that the plug-in coupling is fitted correctly (must engage audibly) by pulling the line apart.
18. Switch off ignition, switch off the PIWIS Tester and disconnect adapter line to the vehicle.
Subsequent work
1. Install underbody covers.
-> 519319 Removing and installing cover for centre underbody.
-> 519419 Removing and installing cover for rear underbody.
2. Disconnect the charger.
3. Remove warning sign.