3.152 Series » How to eliminate air from the fuel system

Standard method:

This method is used on the Lucas DPA fuel injection pump. Vent screws (CI and C2) are fitted to this pump.

Self-vent method:

This method is used on the Lucas DP200 Series and the Stanadyne DB2 fuel injection pumps. 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.

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

Standard method

1. Loosen the banjo connection bolt which is fitted on the top of the filter (A1).
2. Operate the priming lever on the fuel lift pump (B) until fuel, free from air, comes from the filter vent point. Tighten the banjo connection bolt. If the drive cam of 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 turned one revolution.
3. Where the fuel filter is fitted lower than the fuel injection pump, loosen the inlet connection at the fuel injection pump (C3) and operate the lift pump to remove any air. Tighten the inlet connection.
4. 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.
5. Loosen the vent screw in the lock screw of the hydraulic head (C1) and the vent screw on the governor cover of the fuel injection pump (C2).
6. Operate the priming lever of the fuel lift pump until fuel, free from air, comes from the vent screw(s). Tighten the vent screw(s).
7. Loosen the union nut (D1) at the fuelled starting aid (if one is fitted) and operate the lift pump until fuel, free from air, comes from the connection. Tighten the union nut at the starting aid.

Caution: 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 nul more, as this can cause a restriction at the end of the pipe. This can affect the fuel delivery.

8. Loosen the union nuts of the high-pressure pipes (B1) 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.
9. The engine is now ready to start.

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

Self-vent method

If the engine has been stopped by air in the fuel system:

Ensure that fuel has been added to the tank or that the leakage has been corrected.

1. If a manual stop control is fitted, ensure that it is in the "run" position.
2. Operate the starter motor until the engine starts.

If the fuel System or a component in the System has been drained:

1. Release the vent plug on the fuel filter head. Operate the priming lever of the fuel lift pump (B) until fuel free of air comes from the vent plug. Tighten the vent plug. If the drive cam of the fuel lift pump is at the point of maximum lift, il will not be possible to operate the priming lever. In this situation the crankshaft must be turned one revolution.

Caution: 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.

2. Loosen the high-pressure connections (E1) at the atomisers. Ensure that the manual stop central, if one is fitted, is in the "run" position. Operate the starter motor until fuel, free of air, comes from the pipe connections. Tighten the connections to 22Nm (2,2 kgf m).
3. The engine is now ready to start.

If the engine runs correctly for a short tîme 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.