Fuel Pump Delivery Quantity, Checking
Fuel Pump Delivery Quantity, Checking
• Voltage supply OK.
• Fuel pressure regulator and residual pressure OK => [ Fuel Pressure Regulator and Residual Pressure, Checking ] Fuel Pressure Regulator and Residual Pressure, Checking
• Fuel filter OK.
- Remove fuel filler cap from fuel filler tube.
- Remove seat bench.
- Unclip cover - 1 - from fuel delivery unit. Arrow - 2 - points in direction of travel.
- Disconnect harness connector - 1 - from fuel delivery unit.
- Place test instrument adapter/DSO (5-pin) (VAS 5565) on the connector and on the fuel delivery unit.
- Connect remote control (V.A.G 1348/3A) to the test instrument adapter/DSO (5-pin) (VAS 5565) and to battery plus (+).
• Delivery rate of Fuel Pump (FP) is measured at 4 bar. Therefore, measure fuel pressure before measuring delivery rate => [ Fuel Pressure Regulator and Residual Pressure, Checking ] Fuel Pressure Regulator and Residual Pressure, Checking.
CAUTION!
Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before loosening the fuel lines, place a rag around the connection point. Then release pressure by carefully pulling hose off connection.
- Disconnect return line - 1 - from fuel pressure regulator.
• Press in securing ring to disengage the fuel line.
- Connect adapter set (V.A.G 1318/17) to fuel pressure regulator and hold end of adapter in a measuring container.
- Operate remote control (V.A.G 1348/3A) approximately 5 seconds in order to fill the fuel filter.
- Empty measuring container.
- Delivery rate of Fuel Pump (FP) is dependent on voltage. Therefore connect multimeter to battery.
- Operate remote control for 30 seconds and measure battery voltage.
- Compare quantity of fuel delivered with specification.
*) Minimum delivery rate cm3/30 s
**) Voltage at fuel pump with engine off and pump running (approximately 2 Volts less than battery voltage).
Example:
During the test, a voltage of 12.5 volts is measured at the battery. Since the voltage at the pump is approximately 2 Volts less than battery voltage, there is a minimum delivery rate of 580 cm3/30 s.
If minimum delivery rate is not attained:
- Check supply line to filter for possible restrictions (kinks) or clogging.
If fuel line is OK:
- Check fuel delivery rate in front of fuel filter.
CAUTION!
Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before loosening the fuel lines, place a rag around the connection point. Then release pressure by carefully pulling hose off connection.
- Disconnect supply line - 1 - from fuel filter input.
• Press in securing ring to disengage the fuel line.
- Connect pressure gauge (V.A.G 1318) to adapter set (V.A.G 1318/17) as shown.
- Connect adapter (V.A.G 1318/1) to adapter (V.A.G 1318/11) of pressure gauge and hold it in a measuring container.
CAUTION!
Danger of spraying when opening shut-off valve! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Hold container in front of free connection of pressure measuring device.
- Open shut-off valve of pressure gauge. Lever will point in direction of flow - A -.
- Operate remote control (V.A.G 1348/3A). Slowly close shut-off tap, until pressure gauge shows 4 bar. From this point on do not move position of shut-off tap.
- Empty measuring container.
- Operate remote control anew for 30 seconds. Compare delivery rate with the value determined from the first measurement.
If minimum delivery rate is now obtained:
- Replace fuel filter.
If minimum delivery rate is again not obtained:
- Remove fuel delivery unit and check filter strainer for dirt.
Only when up to now no malfunction has been detected:
- Replace fuel delivery unit => [ Fuel Delivery Unit ] Service and Repair.
- Reconnect all disconnected fuel lines.
- Bleed fuel supply system => [ Fuel System, Bleeding ] Service and Repair.
Delivery rate has been obtained, but malfunctions are still suspected in the fuel supply, for example sporadic loss of fuel supply:
- Check Fuel Pump (FP) current draw => [ Fuel Pump Current Draw, Checking ] Fuel Pump Current Draw, Checking.