Fuel Delivery, Checking

Checking Fuel Delivery

Test requirements
- Voltage supply OK
- VAG 1348/3A remote control connected

Test sequence
- Remove fuel filler cap from fuel filler tube.







- Disconnect supply line -3- (with white marking) and catch escaping fuel using a rag.


NOTE: Press in securing ring to disengage the fuel lines.


WARNING:
- The fuel or fuel lines in fuel system can become very hot (danger of scalding).
- In addition, the fuel system is under pressure. Before opening the system, place rags around the connection area and release pressure by carefully loosening the connection.
- Wear protective goggles and protective gloves when working on the fuel system.







- Connect pressure gauge (V.A.G 1318) to fuel supply line using adapter ((V.A.G 1318/23) and ((V.A.G 1318/17).
- Connect hose (VAG 1318/16) to adapter (VAG 1318/11) of pressure gauge and hold it in measuring container.
- Open shut-off valve of pressure gauge. Lever will point in direction of flow -A-.
- Operate V.A.G 1348/3A remote control. Slowly close shut-off valve until on pressure gauge 3 bar positive pressure is indicated. Do not change position of shut-off valve any more.
- Empty measuring container.
- Delivery rate of Fuel Pump (FP) is dependent on battery voltage. Therefore, connect multimeter to vehicle battery using adapter cables.
- Operate remote control 30 seconds long and measure battery voltage.







- Compare fuel quantity pumped with specified value.
*)Minimum delivery rate cm cube/30 s
**)Voltage at Fuel Pump (FP) with engine off and pump running (approx. 2 volts less than battery voltage).

Read-out example:

During test, a voltage of 12.2 volts is measured at battery. Since the voltage at the pump is approx. 2 volts less than battery voltage, there is a minimum delivery rate of 200 cm cube/30 s.

If minimum delivery rate is not obtained:
- Check fuel lines for possible restrictions (kinks) or clogging.







- Disconnect supply line -1- from fuel filter input.

NOTE: Depress buttons on hose connections to do so.

- Connect pressure gauge (VAG1318) with adapter (1318/17) to hose.
- Repeat test of delivery rate.

If minimum delivery rate is obtained now:
- Replace fuel filter:
- Vehicles with engine code AEG, AVH, AZG, item 19,
- Vehicles with engine code BDC, item 22.

If minimum delivery rate is still not obtained:
- Remove Fuel Pump (FP) unit and check filter strainer for dirt.

Only if no malfunctions have been found yet:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP), Fuel Pump (FP), removing and installing.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

Delivery rate has been obtained, but malfunctions are still suspected in the fuel supply (e.g. sporadic loss of fuel supply):

- Check Fuel Pump (FP) current draw as follows.
- Re-connect all disconnected fuel lines.







- Connect multimeter with electrical current probe to wire of 4-pin connector (terminal 1 arrow) from wiring harness.
- Start engine and let run at idle.
- Measure Fuel Pump (FP) current draw. Specified value: max. 8 amperes

NOTE: If malfunction in fuel system is sporadic, test can also be performed during a road test, but a second person is required.

If current draw is exceeded:
- Fuel Pump (FP) faulty, replace Fuel Pump (FP) unit, Fuel Pump (FP) unit, removing and installing.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes