SEAL AS 2077107 - Caterpillar

If air enters the fuel system, the air must be purged from the fuel system before the engine can be started. Air can enter the fuel system when the following events occur:
The fuel tank is empty or the fuel tank has been partially drained.
The low-pressure fuel lines are disconnected.
A leak exists in the low-pressure fuel system.
The fuel filter is replaced.Use the following procedure in order to remove air from the fuel system:
Turn the keyswitch to the RUN position. Leave the keyswitch in the RUN position for 3 minutes. If a manual purging screw is installed, the purging screw should be slackened during priming the fuel system.
Illustration 1 g01003929
Typical example
Crank the engine with the throttle lever in the CLOSED position until the engine starts. Note: If necessary, loosen the union nuts (1) on the fuel injection lines at the connection with the fuel injector until fuel is evident. Stop cranking the engine. Tighten the union nuts (1) to a torque of 30 N m (22 lb ft).
Start the engine and run the engine at idle for 1 minute.
Do not crank the engine continuously for more than 30 seconds. Allow the starting motor to cool for two minutes before cranking the engine again.
Cycle the throttle lever from the low idle position to the high idle position three times. The cycle time for the throttle lever is one second to 6 seconds for one complete cycle. Note: In order to purge air from the fuel injection pump on engines with a fixed throttle, the engine should be run at full load for 30 seconds. The load should then be decreased until the engine is at high idle. The procedure should be repeated three times. The procedure will assist in removing trapped air from the fuel injection pump.
Check for leaks in the fuel system.