G333 & 3306 NATURAL GAS ENGINES Caterpillar

General

Proper engine operation and maintenance are essential to long engine life and maximum performance. The essentials for proper operation and normal periodic maintenance are outlined in this guide. However, your Caterpillar dealer is available for troubleshooting and/or repairs when required.

Before starting the engine, familiarize yourself with these procedures and apply the principles to your particular installation.

Safety Precautions

Safety is basically common sense. There are standard safety rules but each situation has its own peculiarities which cannot always be covered by rules. Therefore, your experience and common sense will be your best guides to safety. Watch for hazards. Correct deficiencies promptly.

You can do something about safety. Lack of attention to safety can result in: accidents, personal injury, reduction of efficiency and worst of all-loss of life.

Use the following safety precautions as a general guide to safe operation.

1. Never adjust or repair a machine while in operation.

2. Remove all loose tools and electrical cords from the engine before starting.

3. Keep the engine room and floor area clean.

4. Store oily rags in containers.

5. Never store flammable liquids near the engine.

6. Do not smoke around batteries. Hydrogen gas generated by a charging battery is explosive. Keep batteries in a well ventilated area.

7. Observe NO SMOKING signs.

8. Do not wear loose clothing around machinery.

9. Be sure the engine room is properly ventilated.

10. Always disconnect and tape the ground battery lead before working on the electrical system.

11. All electrical equipment must be grounded according to local building codes.

12. Be sure an automatic start-stop system is inoperative when the engine is being worked on. Disconnect the starter from the start switch.

13. Use the emergency stop button for emergency only. (This procedure shorts out the magneto, thus leaving unburned gas in the manifold.)

14. An overly rich fuel mixture can cause combustion in the exhaust system.

15. All gas lines and valves must meet local codes.

16. Check piping periodically for gas leaks.

Remember, safety is everyone's business.

INSTALL GUARDS ON ALL EXPOSED ROTATING COMPONENTS

Periods Of Limited Use

Prolonged operation at low idle or reduced load may cause oil consumption and carboning in the combustion chamber and result in poor performance and a loss of power. Every four hours, load the engine to clear carbon from the combustion chamber.

If the engine is to be stored or left standing for a long period of time, the lubricating oil may drain away from the cylinder walls and piston rings. This lack of lubricant permits rings to rust, and causes unnecessary wear by metal-to-metal contact between the pistons and rings when the engine is started. The lack of lubricant may not cause any noticeable change in engine operation after it has been started, but it does contribute to shorter engine life.

If an engine is not going to be used for several weeks, renew the oil film by running the engine once a week until it is thoroughly warm. This will circulate the oil and will prevent rust from forming. Lubricate all points mentioned in the lubrication chart.

If an engine is going to be put in winter storage, see your Caterpillar dealer for storage instructions.

Initial Adjustments

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 to 20 psi (20 to 140 kPa). A turbocharged engine must have greater working pressure available, 12 to 20 psi (85 to 140 kPa). 20 psi (140 kPa) is the maximum line pressure which is easily reduced to a working pressure. If gas pressure exceeds 20 psi (140 kPa), 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 Regualtor 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.

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.

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.