Fuel Pump: Testing and Inspection
WM 206601 Checking quantity delivered by fuel pump
Tools
Technical values
Information
Fuel pressure check and fuel quantity check
Information
Before checking the fuel quantity, a pressure check must first be performed in accordance with Guided Fault Finding in the PIWIS Tester or based on the instructions in the repair information. -> 200201 Checking fuel pressure Testing and Inspection
Preliminary work
WARNING
Toxic substances
- Danger of poisoning or suffocation
-> Ventilate the work area well.
-> Never ingest or inhale.
-> Read specific information on the Hazard Sheet.
-> Wear personal protective gear.
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.
Information
- Absorb any escaping fuel using a suitable binding material or a cloth.
- Cloths which have absorbed fuel must be disposed of according to the applicable national laws.
- The fuel system must be depressurised before starting work on it.
- Only work on the fuel system in well-ventilated rooms.
- Any seals which have been removed must always be replaced.
- Do not use any sealant containing silicone or silicone spray when the injection system is open. Traces of silicone drawn in by the engine are not combusted and damage the oxygen sensors.
1. Relieve the fuel pressure =>
1.1. Switch off ignition.
1.2. Pull out the fuse for the fuel pump.
1.3. Start the engine and wait until the engine starts up automatically.
2. Open the filler flap.
3. Remove rear seat. -> 724819 Removing and installing rear seat - section on "Removing" 724819 Removing and installing 1/3-split folding rear seat 724819 Removing and installing 2/3-split folding rear seat
4. Remove the right cap (figure shows both caps) -arrows-. To do this, remove the carpeted floor. Then loosen the four fastening nuts and remove the cap.
Fastening nuts on caps
5. Carefully pull off the fuel supply line -arrow- at the right connection unit (place several cloths underneath to absorb the fuel that squirts out).
Fuel supply and connection points at right connection unit
Tools and materials
Tools for checking fuel pressure and fuel delivery rate
Testing and measuring tools for fuel pressure and fuel delivery rate
Checking fuel delivery rate (low-pressure delivery rate)
Information
If you suspect that a pump in the fuel tank is defective (particularly if symptoms include a very low fuel level), always check the sucking jet pump for dirt or blockages.
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. 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.
Tool setup for testing fuel delivery rate
4. 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 or bucket (with a volume of at least 5 litres) -2-. The stopcock is set to flow.
Connecting measuring tool
5. Connect the Tester and get it ready. PIWIS Tester II 9818
5.1. The fuel pump can be activated and deactivated as follows:
5.2. Diagnostics => Cayenne => DME => Drive link test/Tests => Drive links => Fuel pump 1
5.3. 100% is displayed. The fuel pump starts to deliver fuel when you press Start.
5.4. The fuel pump stops when the percentage value changes to 0%. Press Start again.
6. Activate the 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.
7. Get a second mechanic to help perform the measurement if necessary.
8. Have a stopwatch ready.
9. The fuel pump must deliver at least 3 litres of fuel during an operating time of 1 minute. Continue to measure the fuel for 20 seconds (stopwatch). The measured result in millilitres delivered is multiplied by 3. For example: After pumping for 20 seconds, around 1,050 ml of fuel is measured. Multiplying the result by 3 gives a delivery rate of 3,150 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.
Subsequent work
1. Disconnect tool and reconnect vehicle connections. Absorb and wipe off residual fuel with a cloth.
Fuel supply and connection points at right connection unit
2. Fit the right cap (figure shows both caps). Then tighten the four fastening nuts on each to => Tightening torque: 10 Nm (7.5 ftlb.). Refit carpeted floor and fix in place with double-sided adhesive tape.
Fastening nuts on caps
3. Install rear seat. -> 724819 Removing and installing rear seat - section on "Installing" 724819 Removing and installing 1/3-split folding rear seat 724819 Removing and installing 2/3-split folding rear seat
4. Close the filler flap.
5. Air the vehicle with the windows open.