3406E, C12, C15 and C18 Marine Engines Caterpillar


Can Not Reach Top Engine RPM

Usage:

C-12 9HP
Note: If this problem occurs only under load, refer to Troubleshooting, "Low Power/Poor or No Response to Throttle".

Probable Causes

  • Diagnostic codes

  • Event codes

  • Throttle signal

  • Cold mode

  • Starting aids

  • Intake manifold pressure (boost)

  • Fuel supply

  • Air inlet and exhaust system

  • Accessory equipment

  • Specific conditions

Recommended Actions

Diagnostic Codes and Event Codes

Certain diagnostic codes and/or event codes may cause poor performance. Connect Caterpillar Electronic Technician (ET) and check for active codes and/or logged codes. Troubleshoot any codes that are present before continuing with this procedure.

Throttle Signal

Monitor "Throttle Position" on Cat ET. Verify that the appropriate parameter is programmed to the correct value. Verify that you can achieve full throttle. Refer to Troubleshooting, "System Configuration Parameters" for parameters that are related to the throttles. Refer to Troubleshooting, "Throttle Position Sensor Circuit - Test" for the proper troubleshooting procedure.

Intake Manifold Pressure (Boost)

  1. Monitor "Fuel Position" and "Rated Fuel Limit" on the electronic service tool. If "Fuel Position" does not equal "Rated Fuel Limit", then check the intake manifold pressure.

  1. Monitor the status of the intake manifold pressure on the electronic service tool for normal operation.

Cold Mode

Use the electronic service tool to verify that the engine has exited cold mode. A status flag will appear if the engine is operating in cold mode. This may limit engine speed.

Starting Aids

Verify the correct operation of the air inlet heater (if equipped). For additional information on the air inlet heater, refer to the appropriate Troubleshooting procedure.

Verify the installation of the correct oil grade plug (if equipped). For additional information, refer to the Operation and Maintenance Manual.

Fuel Supply

  1. Check the fuel lines for the following problems: restrictions, collapsed lines and pinched lines. If problems are found with the fuel lines, repair the lines and/or replace the lines.

  1. Check the fuel tank for foreign objects which may block the fuel supply.

  1. Prime the fuel system if any of the following procedures have been performed:

    • Replacement of the fuel filters

    • Service on the low pressure fuel supply circuit

    • Replacement of unit injectors

    Note: A sight glass in the low pressure supply line is helpful in diagnosing air in the fuel.

  1. Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold weather operation.

  1. Check the fuel pressure during engine cranking. Check the fuel pressure on the outlet side of the fuel filter. Refer to Testing and Adjusting for correct pressure values. If the fuel pressure is low, replace the fuel filters. If the fuel pressure is still low, check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve.

Air Inlet and Exhaust System

  1. Clean plugged air filters or replace plugged air filters. Refer to the Operation and Maintenance Manual.

  1. Check the air inlet and exhaust system for restrictions and for leaks. Refer to Testing and Adjusting for additional information.

Accessory Equipment

Check all accessory equipment for problems that may create excessive load on the engine. Repair any damaged components or replace any damaged components.

Check the actual size of the prop. An oversized prop can cause an engine overload. Install the recommended prop if an oversized prop is being used.

Specific Conditions

An engine overload may be caused by specific conditions which may exist. The following two conditions can cause this problem.

  • Obstructions on the hull may have buildup which can cause the engine to be overloaded. Refer to Operation and Maintenance Manual for the correct procedure to clean the hull.

  • Check the water line on the vessel. The water line may indicate a condition of excessive weight. The water line may also indicate an improper weight distribution. Refer to Operation and Maintenance Manual for more information.

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