Checking Fuel Delivery Rate (Low Pressure Delivery Rate) On Dfi Engines

Information 

If you suspect that the pumps in the fuel tank are defective (particularly if symptoms include a very low fuel level), always check the sucking jet pumps for dirt or blockages. A piping diagram and assembly overview are shown in the information section for the fuel pumps. → 206619 REMOVING AND INSTALLING FUEL PUMP (IN-TANK FUEL PUMP) ON DFI ENGINES 

1. Open the bonnet.
2. Connect a charger to the vehicle battery. The voltage should be approx. 12.5 V (no rapid charging allowed because the voltage is too high!).
3. Open the cover over the fuse box. Open the lid of the central electrics box. To do this, loosen the four fastening screws.
   Fig 1: Locating Central Electrics Box

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.
4. Pull out both fuel pump relays (for latest assignment, see wiring diagram). One relay supplies the right-hand fuel pump, while the other supplies the left. Adapter 9479  must be inserted into the slot for the fuel pump to be checked (both can be checked). Make sure that the switch is at "0".
5. Connect pressure gauge with stopcock tester K-Jetronic Tester V.A.G. 1318 WE 1291  using adapter 1318/7 and connecting line connection line 9705/3  ("female" rapid-action coupling) on the side of the stopcock. On the other side of the stopcock, connect connecting line 1318/17 (A) with measuring adapter 9705  . The tool setup must be fitted with sealing rings (copper, aluminium, or plastic etc.) between the individual components. The setup must be fully sealed.
   Fig 2: Identifying Tool Setup For Testing Fuel Delivery Rate

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.

1. Measuring adapter 9705;  with rapid-action coupling => used for checking the fuel delivery rate. Generates the required counter-pressure of 2.5 bar.
2. Adapter 1318/17 (A) from K-Jetronic Tester V.A.G. 1318 WE 1291;  connection to measuring adapter 9705  => used for checking the fuel delivery rate.
3. Pressure gauge with stopcock tester K-Jetronic Tester V.A.G. 1318 WE 1291 
4. Adapter 1318/7 from K-Jetronic Tester V.A.G. 1318 WE 1291 
5. Connecting line connection line 9705/3  ("female" rapid-action coupling)
6. Connect measuring tool to the output of the connection unit -1-  . Hold open end of hose of measuring adapter 9705  into a large measuring tub (with a volume of at least 1 litre) -2-  . The stopcock is set to flow.
   Fig 3: Connecting Measuring Tool

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.
7. By briefly actuating the adapter 9479  , actuate the selected fuel pump and remove all air from the measuring apparatus. Ensure that the open part of the hose is securely retained in the measuring tub. Remove the rest of the pumped fuel from the measuring tub.
8. Get a second worker to help perform the measurement if necessary.
9. Each fuel pump must deliver at least 1.8 litres of fuel during an operating time of 1 minute  . The measurement should be performed for 20 seconds  (stopwatch), as the fuel pumps will switch off after 1 minute. The measured result in milliliters delivered is multiplied by 3. For example: After pumping for 20 seconds, around 750 ml of fuel is measured. Multiplying the result by 3 gives a delivery rate of 2.250 litres per minute. The pressure gauge shows a fuel pressure of 2.5 to 2.7 bar during the measurement. This pressure is generated by the counter-pressure of the pressure regulator at the measuring adapter 9705  .