G3406 Engine Caterpillar

Carburetor - Adjust

Usage:

Throttle Linkage

Adjust the throttle linkage according to the engines Specifications.

Load Adjusting Valve

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Table 1
Tools Needed
391-8170 EMISSIONS ANALYZER TOOL GP - (Bluetooth Module) ⁽¹⁾		1
393-0673 EMISSIONS ANALYZER TOOL GP ⁽¹⁾		1
1U-5470 Engine Pressure Group		1

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^( 1 )

Either analyzer may be used.

The load adjusting valve affects the air/fuel ratio. The valve determines whether the mixture is rich or lean. The following factors are influenced by the air/fuel ratio:

Fuel consumption
Engine power output
Engine stability
Engine component life
Deterioration of lube oil

After the gas pressure regulator, the load adjusting valve regulates the amount of fuel to the carburetor. The load adjusting valve is initially adjusted in order to provide sufficient fuel for engine start-up. After the engine is running, the load adjusting valve is used to obtain the desired exhaust emissions.

The most accurate method of adjusting the air/fuel ratio involves the use of an emissions analyzer. This method consumes the least amount of time as well.

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Illustration 1	g00820364
(1) Plug in the exhaust elbow

Remove plug (1) from the exhaust elbow. Install the sensor for the emissions analyzer.

Use the 1U-5470 Engine Pressure Group to measure the inlet manifold air pressure.
The load can be estimated by using the inlet manifold air pressure. For information on estimating the load, refer to Special Instruction, SEHS7341.
For generator set engines, the load can be determined by the electricity that is generated.

Note: Newer engines use the VariFuel 400 carburetor. Earlier engines were equipped with the Impco 200 carburetor.

Set the load adjusting valve.
1. For initial setting of the VariFuel 400 carburetor, turn load adjusting valve (2) clockwise to the fully closed position. Then turn the load adjusting valve for four full turns in the counterclockwise direction.
1. For initial setting of the Impco 200 carburetor, turn load adjusting valve (2) to the center between the "L" and the "R".
  The "L" represents a lean fuel mixture. The "R" represents a rich fuel mixture.

Start the engine. Operate the engine with a partial load and allow the engine operation to stabilize.

Use the emissions analyzer to check the levels of O₂ and NO_x.

Slowly adjust the load adjusting valve until the desired exhaust emissions are obtained.
For a leaner mixture of air and fuel, turn the load adjusting valve clockwise. To richen the mixture of air and fuel, turn the load adjusting valve counterclockwise.

Increase the load. Adjust the exhaust bypass valve, if necessary. Refer to Testing and Adjusting, "Exhaust Bypass Valve".

Monitor the position of the throttle plate, the desired engine rpm at full load, and the exhaust emissions. Continue to adjust the load adjusting valve and the exhaust bypass valve. Make adjustments until the engine is operating at full load with a throttle angle of approximately 70 degrees.