1000 series » How to eliminate air from the fuel system

There are two methods to eliminate air from the fuel system according to the type of fuel injection pump fitted:

The standard method is used where the fuel injection pump has vent screws (A1/2) and (B1).

The self-vent method is used where the fuel injection pump has a self-vent feature. These pumps have a vent pipe (C1) fitted between a connection in the top of the pump and the atomiser leak-off pipe. Vent screws are not fitted to these pumps.

If air enters the fuel system, it must be eliminated before the engine can be started.

Air can enter the system if:

• The fuel tank is drained during normal operation.
• The low-pressure fuel pipes are disconnected.
• A part of the low-pressure fuel system leaks during engine operation.

If air enters the fuel system, it must be eliminated before the engine can be started.

In order to eliminate air from the fuel system, proceed as follows:

Caution: Do not allow fuel from the engine to contaminate the engine compartment. Put a drip tray under the engine and discard old fuel in accordance with local instructions.

Standard method to eliminate air from the fuel system

1. Loosen the vent plug on the top of the twin element fuel filter (A1). If a single element filter is used, loosen the banjo connection bolt which is fitted on the top of the filter (B1).
2. Operate the priming lever on the fuel lift pump (C) until fuel, free from air, comes from the filter vent point. Tighten the vent plug or banjo connection bolt.

   Note: If the cam for the fuel lift pump is at the point of maximum lift, it will not be possible to operate the priming lever. In this situation, the crankshaft must be rotated one turn.

3. Ensure that the manual stop control is in the "run" position. If an electrical stop control is used, turn the start key to the "R" position.
4. Loosen the vent screw in the lock screw (D2) for the hydraulic head. Operate the priming lever of the fuel lift pump until fuel, free from air, comes from the vent screw. Tighten the vent screw. Loosen the vent screw (B1) on the governor cover. Operate the priming lever of the fuel lift pump until fuel, free from air, comes from the vent screw. Tighten the vent screw.

Caution: Use a spanner on the flats (A1) of the fuelled starting aid to prevent its movement when the union nut (A2) is loosened and tightened.

5. If the pipe to the fuelled starting aid has been drained, loosen the union nut (A2) at the fuelled starting aid and operate the lift pump (C) until fuel, free from air, comes from the connection. Tighten the union nut at the starting aid. Use a spanner on the hexagon of the fuelled starting aid to prevent its movement when the union nut is loosened and tightened.
6. Loosen the union nuts (B1) of the high-pressure pipes at two of the atomisers. Operate the starter motor until fuel free from air, comes from the pipe connections. Tighten the high pressure-pipe connections to 27 Nm (20 lbf ft) 2,8 kgf m.
7. The engine is now ready to start. If the engine runs correctly for a short time and then stops or runs roughly, check for air in the fuel system. If there is air in the fuel system, there is probably a leakage in the low pressure system.

Self-vent method

Fuel injection pumps used on some Lucas and all Stanadyne fuel injection pumps will automatically remove air from the fuel system. Vent screws are not fitted to these pumps.

Caution: Although these fuel injection pumps will eliminate air automatically, use the procedure that follows to remove air from the fuel system if the system is drained or a major component is removed: Ensure that fuel has been added to the tank or that the leakage has been corrected.

1. Loosen the vent plug (A1) on the top of the filter head.
2. Operate the priming lever on the fuel lift pump (B) until fuel, free from air, comes from the filter vent point. Tighten the vent plug.

Note: If the cam for the fuel lift pump is at the point of maximum cam lift, it will not be possible to operate the priming lever. In this situation, the crankshaft must be rotated one turn.

Caution: Use a spanner on the flats (A1) of the fuelled starting aid to prevent its movement when the union nut (A2) is loosened and tightened.

3. If the pipe to the fuelled starting aid has been drained, loosen the union nut (C2) at the fuelled starting aid and operate the lift pump (C) until fuel, free from air, comes from the connection. Tighten the union nut at the starting aid. Use a spanner on the hexagon of the fuelled starting aid to prevent its movement when the union nut is loosened and tightened.

Cautions:

• Do not tighten the union nuts of the high-pressure pipes more than the recommended torque tension. If there is a leakage from the union nut, ensure that the pipe is correctly aligned with the atomiser inlet. Do not tighten the atomiser union nut more, as this can cause a restriction at the end of the pipe. This can affect the fuel delivery.
• Damage to the fuel injection pump, battery and starter motor can occur if the starter motor is used excessively to eliminate air from the fuel system.

If the engine runs correctly for a short time and then stops or runs roughly, check for air in the fuel system. If there is air in the fuel system, there is probably a leakage in the low-pressure system.