889152 Mercruiser VALVE, Boiler

Table 1
Tools Needed Quantity
8T-5160 Gas Regulator Setting Tool 1
1U-5470 Engine Pressure Group 1 Gas Pressure to the Gas Pressure Regulator
Make sure that the pressure of the gas to the gas pressure regulator is sufficient. Table 2 lists the gas pressure that is required for the gas pressure regulator.
Table 2
Requirements for Gas Pressure to the Gas Pressure Regulator
Fuel System Pressure
Low pressure gas (1) 10 to 35 kPa (1.5 to 5 psi)
High pressure gas (2) 83 to 172 kPa (12 to 25 psi)
(1) Naturally aspirated engines and turbocharged engines
(2) Turbocharged engines
Use only properly designated Caterpillar gas pressure regulators.
Pressure of the Gas Supply To the Carburetor
The gas pressure regulator maintains a pressure differential between the air and the fuel that is supplied to the carburetor. After setting, the gas pressure regulator will maintain the pressure differential in response to changes in the air pressure.Determine whether the pressure regulator uses positive pressure or negative pressure.For engines with dual fuel systems, both of the regulators must be adjusted.Adjusting the Positive Pressure Regulator
Make sure that the gas to the gas pressure regulator is shut 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 1 g00810413
Typical arrangement for low pressure gas
(1) Plug in the gas line to the carburetor
(2) Air filter service indicator on the air cleaner
(3) Cap on the gas pressure regulator
For low pressure gas, remove plug (1). Remove service indicator (2) from the air cleaner. Attach the lines for the differential pressure gauge of the 1U-5470 Engine Pressure Group into the openings.
Illustration 2 g00810415
Typical arrangement for high pressure gas
(1) Plug in the gas line to the carburetor
(2) Plug in the balance line from the aftercooler
(3) Cap on the gas pressure regulator
For high pressure gas, remove plugs (1) and (2). Attach the lines for the differential pressure gauge of the 1U-5470 Engine Pressure Group into the openings.
Remove cap (3). The adjusting screw for the gas pressure regulator is under the cap.
Turn ON the gas supply to the gas pressure regulator. Observe the pressure differential. The correct pressure of the gas is 1 to 1.2 kPa (4 to 5 inches of H2O) HIGHER than the atmospheric pressure.
If necessary, turn the gas pressure regulator's adjusting screw in order to obtain the desired pressure. Use the 8T-5160 Gas Regulator Setting Tool or use a large screwdriver to turn the adjusting screw.
Start the engine. Operate the engine at rated speed (no load). Observe the pressure differential. Adjust the gas pressure again, if necessary.
Stop the engine. Turn OFF the gas supply to the gas pressure regulator.
Remove the lines for the differential pressure gauge. Install the original parts (1), (2), and (3) into the openings.
Turn ON the gas supply to the gas pressure regulator. Adjusting the Negative Pressure Regulator
Make sure that the gas to the gas pressure regulator is shut OFF. Note: A water manometer may be used instead of the 1U-5470 Engine Pressure Group.
Illustration 3 g00778139
Typical arrangement for negative pressure gas
(1) Plug in the gas line to the carburetor
(2) Cap on the gas pressure regulator
Remove plug (1). Remove the service indicator from the air cleaner. Attach the lines for the differential pressure gauge of the 1U-5470 Engine Pressure Group into the openings.
Remove cap (3). The adjusting screw for the gas pressure regulator is under the cap.
Turn ON the gas supply to the gas pressure regulator. Observe the pressure differential. The correct gas pressure is approximately −0.25 kPa (−1 inch of H2O) LOWER than the atmospheric pressure.
If necessary, turn the gas pressure regulator's adjusting screw in order to obtain the desired pressure. Use the 8T-5160 Gas Regulator Setting Tool or use a large screwdriver to turn the adjusting screw.
Start the engine. Operate the engine at rated speed (no load). Observe the pressure differential. Adjust the gas pressure again, if necessary.
Stop the engine. Turn OFF the gas supply to the gas regulator.
Remove the lines for the differential pressure gauge. Install plug (1) and install the service indicator. Install cap (3).
Turn ON the gas supply to the gas pressure regulator.