BEARING 3994731 - Caterpillar

Introduction
For Specifications with illustrations, make reference to Specifications For 3412 Generator Set Engines, Form No. SENR6482. If the Specifications in Form SENR6482 are not the same as in the Systems Operation and the Testing And Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.Fuel System
Either too much fuel or not enough fuel for combustion can be the cause of a problem in the fuel system. Many times work is done on the fuel system when the problem is really with some other part of the engine. The source of the problem is difficult to find, especially when smoke comes from the exhaust. Smoke that comes from the exhaust can be caused by a defective fuel injection nozzle, but it can also be caused by one or more of the reasons that follow:1. Not enough air for good combustion.2. Oil leakage into combustion chamber.3. Not enough compression.Fuel System Inspection
A problem with the components that send fuel to the engine can cause low fuel pressure. This can decrease engine performance.1. Check the fuel level in the fuel tank. Be sure that the fuel tank is properly vented.2. Check the fuel lines for fuel leakage. Be sure the fuel supply line does not have a restriction.3. Install a new fuel filter. Clean the primary fuel filter.4. Remove any air that may be in the fuel system. Use the fuel priming pump to move fuel through low pressure part of the system. Fuel with air will return to the tank through the fuel return line.To remove air from the fuel injection lines, loosen the fuel line nuts at the through the head adapter nozzles 1/2 turns. Crank engine with the starter motor until fuel (without air) comes from the fuel line connections. Tighten the fuel line nuts. The fuel priming pump will not give enough pressure to push fuel through the orificed reverse flow check valves in the fuel injection pumps.Fuel Transfer Pump
With the engine operating at full load speed, the fuel transfer pump receives fuel from the primary fuel filter. Fuel then moves through the ECM and the secondary fuel filters to the fuel injection pump.To check the fuel transfer pump pressure, disconnect the fuel line (from the filter) at the fuel injection pump housing inlet. Install a tee at the inlet and connect the fuel line to the tee. Connect a pressure gauge to the tee and start the engine. Fuel is delivered to the fuel pump housing at approximately 414 kPa (60 psi) at full load speed.If the fuel pressure is not up to specifications, stop the engine. Make a replacement of the primary and secondary fuel filters and check to make sure the fuel lines and hoses are not plugged or damaged.Start the engine and again check the fuel pressure. If the fuel pressure is not at specifications, a repair or replacement of the fuel transfer pump is needed.Checking Engine Cylinders Separately
An easy