ORIFICE AS 4785760 - Caterpillar

Do not attempt to start the engine until the fuel injection pump has been primed with fuel and air has been removed from the fuel lines. Serious damage to the fuel injection pump can occur if the system is not correctly primed.
Illustration 1 g00734088
The plunger (1) is used to prime the fuel system. The plunger is located on the left side of the engine compartment. The plunger is on top of the fuel/water separator.
Open the engine access door.Note: Refer to Operation and Maintenance Manual, "General Hazard Information" for information on Containing Fluid Spillage.
Loosen the fitting (2) on the fuel/water separator. Push down repeatedly on the plunger (1) to prime. Continue to operate the plunger until fuel that is free of air flows from the fitting. Tighten the fitting.
Start the engine. If the engine does not start, further priming is necessary. If the engine starts but the engine continues to misfire, further priming is necessary. If the engine continues to emit smoke, further priming is necessary.
If the engine starts but the engine runs rough, continue to run the engine at low idle until the engine runs smoothly.