TRANSMISSION AR 3P0300 - Caterpillar

Illustration 1 g00520833
Fuel Ratio Control (1) Inlet port (2) Fuel Ratio Control (FRC) (3) Lever (4) Retainer (5) Spring (6) Diaphragm (7) Spring (8) Retainer shaftThe turbocharged engine uses a simple fuel ratio control (FRC) to control smoke during acceleration at low boost. This FRC is a pneumatic type. FRC (2) restricts the amount of fuel to the combustion chambers until sufficient boost pressure is achieved.Fuel ratio control operates on air pressure that is delivered by a tube between inlet port (1) and the inlet manifold of the engine. At low boost pressure, retainer shaft (8) is held stationary by springs (5) and (7) inside FRC (2). When the operator demands more fuel, the internal governor linkage moves in the fuel on direction until lever (3) contacts retainer (4). At this position, additional fueling is prevented.As engine power increases, boost pressure also increases. This pressure acts against diaphragm (6). When boost pressure is sufficient, spring force is overcome and retainer shaft (8) moves to the right. This permits lever (3) to move allowing the internal governor linkage to move further in the fuel on direction.Tamper Resistant Plugs
Illustration 2 g00685667
(9) Typical location of 128-4786 Plug
Illustration 3 g00685669
(10) Typical location of 128-4794 Plug In 1996, the EPA Emission Regulations began requiring engines to be equipped with some type of tamper resistant device. 3114, 3116 and 3126 Engines that have mechanical unit injection will be equipped with tamper resistant plugs in the governor housing. The tamper resistant plug will prevent unauthorized changes to the FRC. 3114, 3116 and 3126 Engines currently have two sizes of tamper resistant plugs that are being used. Figure 2 shows the typical location of a 128-4786 Plug (9) that has 7/8 inch threads. Figure 3 shows the typical location of a 128-4794 Plug (10) that has 1 5/8 inch threads.If an adjustment is required on a 3114, 3116 or on a 3126 Engine that is equipped with a tamper resistant plug, a 148-3605 Wrench is required in order to remove the tamper resistant plug.