Usage:
The Primary Engine Checks consist of quick and easy procedures that could identify the problem with a minimum loss of time. Always make these checks before starting the more involved troubleshooting procedures.
Whenever a problem is found and corrected, always run the test again to that point to be sure there is not a combination of problems. When the problem has been corrected and the complaint resolved, stop the test. Do not continue through the complete procedure unless it is necessary.
Possible Causes/Corrections
Prestart Checks
Make sure the air filter elements are in good condition and are not plugged. Also, make sure the engine oil and coolant are at the correct levels.
Check Accelerator Linkage
To check the linkage adjustment, push the pedal down until it hits the stop. If the linkage adjustment is correct, the governor linkage will move to the break-over position when the pedal is against the stop. This is shown by clearance on both sides of the tang (see the illustration). When there is clearance on both sides of the tang, the governor linkage is adjusted correctly to permit the engine to operate at high idle. If clearance is not present on both sides of the tang, adjust the governor linkage to give the needed clearance.
Governor Control Linkage Adjustment
(1) Clearance on both sides of tang. (2) Governor control linkage. (3) Pedal (full travel). (4) Governor control. (5) Lever assembly.
Check Vehicle Tachometer
Install the 6V3121 Multitach Group. Start the engine and make sure that the vehicle tachometer is accurately indicating engine rpm. Some electric vehicle tachometers can be adjusted. Correct the tachometer as required. A defective tachometer can cause operation at the wrong engine rpm, this can give the feel of low power.
Check For Air In The Fuel
Disconnect the fuel return line. With the engine in operation, let the fuel from the injection pump housing flow into a container. Look for air bubbles in the fuel coming from the return line. Approximately 5 to 100 visible air bubbles in the fuel is normal. If there is excessive air in the fuel find the cause and correct it. Such as checking all fuel lines and connections for leaks and repair or replacement of parts as needed.
Check Fuel API Gravity Rating
Caterpillar diesel engines are set in production to produce rated power with a fuel of 35 API gravity (0.85 specific gravity). This limit provides a grade of fuel that aids engine starting and avoids vapor lock. Fuel with higher API gravities (i.e., lower specific gravities), will produce less horsepower at the factory power setting and vice versa for lower than 35 API gravity fuels. The engine fuel setting should not be adjusted to compensate for a power loss with fuels lighter than 35 as fuel system component life may be decreased.
For more information refer to SEBD0717, Diesel Fuels And Your Engine. Also, Special Instruction, SEHS6947 has fuel correction factors and tables.
Check For Proper Fuel Heater Application
Make sure that fuel heaters are correctly used. In some cold climates, fuel heaters can be necessary for proper winter performance. The fuel heaters should be shut off in summer or hot weather climate operation. If the fuel temperature is checked, measure it at the fuel filter base.
Check Exhaust Smoke At Low Idle And Under Acceleration
The exhaust smoke can also give an indication of engine performance. Follow the procedures given in the two sections on Excessive Exhaust Smoke.