Checking Fuel Delivery Rate (Low Pressure Delivery Rate) on DFI Engines

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

Tools







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.

Relieve the fuel pressure

1. Switch off the ignition.
2. Pull out fuse 13 and 14.
3. Start the engine and wait until the engine starts up automatically.
4. Loosen rear seat and fold it up. Secure to the headrest using a piece of wire if necessary.
5. Loosen reinforcement plate for right seat-belt buckle. To do this, loosen the three fastening screws and twist the plate with the seat-belt buckle to the side. Do not use the fastening screws again.







6. Loosen the right cap (figure shows both) -arrows-. To do this, remove the carpeted floor. Then unscrew the four fastening nuts and remove the cap.







7. Carefully detach the fuel supply line -1- at the right connection unit (place several cloths underneath to absorb the fuel that squirts out).
8. After opening the fuel line, connect the measuring tool immediately and re-insert the fuses for the fuel pumps.

Tools and materials

Tools for checking fuel pressure and fuel delivery rate







Adapting adapter 9479







1. The adapter 9479 -2- must be adapted to suit the slots on terminal 30 and 87 of the fuel pump relays using two short auxiliary lines -1-. The auxiliary lines are shop-made or lines from a suitable measuring equipment range can be used.







Pull off the fuel pump relays for both fuel pumps in the central electrical system. Instead of the contacts on terminal 30 and 87 of the relay, the two contacts on the auxiliary lines are used to activate the fuel pump (left or right).







2. Select the correct slots for the left or right fuel pump. -1 and 2-.







3. Adapter 9479 must be inserted at the contacts using auxiliary lines. The left or right fuel pump in the tank can now be activated, depending on the slot.

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.

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.
4. Pull out both fuel pump relays (for latest assignment, see wiring diagram). One relay supplies the righthand 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.







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.
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 millilitres 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.

Subsequent work
1. Disconnect tool and reconnect vehicle connections. Absorb and wipe off residual fuel with a cloth.
2. Fit cover plate.
3. Fit seat belt.
4. Fit rear seat.
5. Air the vehicle with the windows open.