0512682 JOHNSON COVER, Battery cable

Gas Supply to the Gas Pressure Regulator
To prevent particles from entering the engine, install a 1 micron fuel filter 1 m (3 ft) before the gas pressure regulator. Install a 321-6970 Fuel Filter Gp with the 4P-4720 Fuel Filter Element in the gas supply line to the regulator.Also install a pressure gauge on each side of the fuel filter to monitor filter restriction. To facilitate servicing of the filter, a shutoff valve should be installed on the supply side of the filter.For low-pressure gas, a supply pressure of 10 kPa to 35 kPa (1.5 psi to 5 psi) is required for the gas pressure regulator with 24 kPa to 35 kPa (3.5 psi to 5 psi) Optimal.Fluctuations of the supply pressure may affect the air/fuel ratio for the engine. For low-pressure gas fuel systems, the maximum fluctuation that is allowed in the supply gas pressure to the engine is 1.7 kPa ( 0.25 psi).
Use only properly designated Caterpillar gas pressure regulators.
Check the Installation of the Gas Pressure Regulator
Illustration 1 g02411864
Line connections to the gas pressure regulator
(1) Balance line
(2) Compensation sensing lineCarefully inspect the condition of balance line (1) and compensating line (2) at both ends. Ensure that the line fittings are not leaking.Ensure that the lines are not kinked or damaged. Damage to one of the lines could compromise the operation of the gas pressure regulator. If the condition of either of the lines is questionable, replace the line.Adjusting the Gas Pressure Regulator
The gas pressure regulator maintains a pressure differential between the air and the fuel that is supplied to the carburetor. After the initial setup, the gas pressure regulator will maintain the pressure differential in response to changes in the carburetor air pressure. Refer to the "High and Lower Heating Value Fuels" graphs to obtain the differential pressure setting for the correct air/fuel ratio. The value obtained from the graph will provide the optimum value for optimum engine start-up. The setting will also provide for stable engine operation during no-load operation.Adjusting the Regulator
Ensure that the gas supply to the regulator is turned off.Note: A water manometer may be used instead of the 1U-5470 Engine Pressure Group.
Attach the lines for the differential pressure gauge of the 1U-5470 Engine Pressure Group.
Illustration 2 g02410997
Typical arrangement for a low-pressure gas engine
(1) Air filter service indicator
(2) Plug
(3) Cap
Perform the following procedure for low-pressure gas carburetors:Remove plug (1) from the fuel line to the carburetor. Remove service indicator (2) from the air cleaner housing. Attach the lines for the differential pressure gauge of the 1U-5470 Engine Pressure Group into these ports.
Remove cap (3) from the housing of the gas pressure regulator.
Determine the "High and Lower Heating Value Fuels" graph that is for your engine. To obtain the correct pressure differential, locate the intersection of the BTU value on the line that represents the carburetor that is for your engine. Locate the intersection on the scale for the dependent variable to the left of the graph (differential pressure). This graph will provide the optimum value for engine starting. This value will also provide stable engine operation with no engine load.
If necessary, adjust the gas pressure regulator adjustment screw to obtain the desired pressure. Use the 8T-5160 Gas Regulator Setting Tool or use a large screwdriver to turn the adjustment screw. Turn the adjustment screw clockwise to increase the pressure, turn the screw counterclockwise to decrease the pressure.
Turn on the gas supply to the gas pressure regulator. Start the engine. Observe the pressure differential. This setting will generally be between 0.87 to 1.5 kPa (3.5 inches to 6 inches of H2O) for these engines.
Stop the engine. Turn off the gas supply to the gas pressure regulator.
Remove the lines for the differential pressure gauge. Restore the fittings to the original configuration.
Turn on the gas supply to the gas pressure regulator. Return the engine to service.High and Lower Heating Value Fuels Graphs
Lower Heating Value Fuels
Illustration 3 g02142347High Heating Value Fuels
Illustration 4 g02142374