Usage:
Before making initial adjustments, check the engine and installation as you would during normal operation. See page 4.
Carburetor Adjustment
CARBURETOR ADJUSTMENTS
1. Idle Adjustment Screw 2. Power Mixture Screw
- 1. Set the power mixture screw (2) midway between "L" and "R".
- 2. Turn the idle adjustment screw (1) clockwise all the way in, then out four turns.
- 3. Set low idle speed on a cold engine. With the engine running, turn the low idle screw (1) to obtain recommended low idle speed (see the Engine Information Plate).
Change the gas pressure delivered by the line pressure regulator to compensate for any change in heat content of the fuel. See your Caterpillar dealer for pressure settings.
Linkage Adjustment
- 1. Disconnect linkage (1).
- 2. Turn screw (2) counterclockwise until the throttle plate will close without touching the screw.
- 3. Turn screw (2) until it touches stop (3) with the throttle plate closed.
LINKAGE ADJUSTMENTS
1. Governor Linkage 2. Throttle Stop Screw 3. Stop
- 4. With the governor lever in the OFF position and the throttle plate closed, adjust the linkages and reconnect them. (If additional linkage adjustment is necessary, see your Caterpillar dealer.)
- 5. On Vee engines adjust linkage so that both throttle plates open simultaneously.
Gas Line Pressure
Gas line pressure must be regulated for use in engines. Naturally aspirated engines, using a line pressure regulator, require line pressure of 3 PSI to 20 PSI. A turbocharged engine must have greater working pressure available- 12 PSI to 20 PSI. Twenty PSI is the maximum line pressure which is easily reduced to a working pressure. If gas pressure exceeds 20 PSI, a second regulator will have to be used.
Line Pressure Regulator
The line pressure regulator requires adjustment when the engine is installed, when the regulator is reworked, or when the heat content of the fuel is changed. A water manometer is used to set the regulator output gas pressure.
- 1. Remove plugs (1) and (2) from the carburetor.
CARBURETOR
1. Air Pressure Manometer Plug 2. Gas inlet Plug 3. Power Mixture Screw
- 2. Connect a water manometer between the two pressure taps.
LINE PRESSURE REGULATOR
4. Regulator Adjustment Plug
NOTE: A valve is used between the manometer and the carburetor to prevent water from being drawn into the engine during start up. Close the valve during cranking and start up, then open the valve when engine is running.
- 3. Open the main gas valve.
- 4. Adjust the gas pressure to support a 51/2 inch (14 cm) column of water, or to correct differential if fuel BTU is known.
- 5. The regulator adjustment is made by removing plug (4) and turning the slotted cap clockwise to increase output pressure and counterclockwise to decrease pressure.
- 6. Repeat this procedure for each carburetor.
- 7. After these initial adjustments the engine can be started.
Adjusting Line Pressure Regulator With Known BTU Fuel
- 1. With known BTU fuel, refer to a differential and BTU curve. See Form FE036044, or see your Caterpillar Dealer for pressure setting.
- 2. Use the curve to find proper differential setting which gives the correct air fuel ratio.
- 3. Follow procedure under line pressure regulator until adjusted gas pressure will support the proper differential with engine at idle condition.
Adjusting Line Pressure Regulator With Unknown BTU Fuels
- 1. Follow procedure under line pressure regulator for setting which will allow starting of engine.
- 2. Install accurate tachometer on engine.
- 3. Remove line regulator plug (4) and install adjusting tool.
NOTE: On turbocharged engines a special tool is necessary to prevent boost pressure from escaping when regulator cap is removed.
- 4. Start engine and put under constant fixed load. Load should be as near full load as possible with engine running steady.
- 5. Physically lock carburetor throttle plate in position while engine is operating. (On Vee Engines lock both throttle plates.)
- 6. Disconnect governor linkage.
- 7. Adjust regulator slotted cap to get maximum engine RPM. Maximum engine RPM can be found best by starting with a lean mixture and slowly increasing to reach maximum RPM.
- 8. Reduce the maximum obtainable RPM by 3%. This is done by leaning mixture - turn slotted cap counterclockwise in regulator. This will give proper air fuel ratio.
NOTE: On Vee Engines each side has to be adjusted separately.
- 9. Reconnect governor linkage and unlock throttle plate.
- 10. Remove special tool from regulator or install cap.
- 11. If differential is desired, a manometer may be installed at carburetor point 1 and 2 and read.
Adjusting Power Mixture Screw -
- 1. Power mixture screw (3) should be adjusted with engine operating at rated load and RPM only.
- 2. Increase richness until engine reaches its maximum RPM.
- 3. Turn power mixture screw to lean until engine loses RPM.
- 4. Turn power mixture screw to rich until engine regains highest RPM.
NOTE: Power mixture screw is only effective at rated load and RPM. With 905 BTU LHV fuel mixture, screw should be set 21/2notches from lean.
Balance Line
Turbocharged engines have a balance line from the carburetor to the line pressure regulator. The balance line transmits manifold air pressure to the upper side of the regulator diaphragm. This force, added to the spring force, ensures that gas pressure to the carburetor will always be greater than inlet air pressure regardless of load conditions. A turbocharged engine will not develop full power without a balance line.
Throttle Synchronization - Vee Engines
Be sure both linkages have been adjusted.
Two turbochargers are used on Vee engines. The air induction system is cross blown, that is, the turbocharger turbine wheel is driven by the exhaust from one bank and the compressor wheel supplies air to the opposite bank. This reduces the amount of unbalanced load possible and keeps one bank from overworking. The maximum amount of unbalance without a loss of power is .3 inches (0,76 cm) of mercury. Unbalance is determined in the following manner.
MANOMETER CONNECTION LOCATION
With the engine stopped:
- 1. Remove the plug from each manifold and connect the manometer.
- 2. Close the valve on the manometer and start the engine. Open the valve.
- 3. Run the engine at 2/3 rated speed and adjust the throttle linkage until the difference in the two columns is within .3 inches (0,76 cm) of mercury. DO NOT change gas pressure to balance the output.
- 4. Repeat Step 3 with engine at 2/3 load and at rated speed.