GEAR-BEVEL 3T8469 - Caterpillar

Probable Causes
Cold cylinder
Electrical connectors or power supply
Ignition system
Incorrect base timing
Fuel supply
Incorrect air/fuel ratio
Incorrect governor adjustment
Compressor bypass valve
Exhaust bypass valve
Air inlet restriction
Exhaust restriction
Throttle valve differential pressure sensor
Throttle actuator
Incorrect valve lash
Cylinder head and related components
Fuel Metering ValveRecommended Actions
Note: If the symptom only occurs under certain operating conditions (high idle, full load, engine operating temperature, and so on), test the engine under the conditions. Troubleshooting the symptom under other conditions can give misleading results.Cold Cylinder
Use the exhaust temperature scanner to view the temperatures of each individual cylinder. Compare the temperature readings in order to identify a cold or misfiring cylinder. Refer to Systems Operation/Testing and Adjusting, KENR5473, "Exhaust Temperature Module" for information related to use of the exhaust temperature scanner.If there is an indication of a misfiring cylinder, check the following components for problems:
Spark plugs
Extenders
Ignition transformers
Primary wiring for the ignitionInspect each of the extenders for signs of pin holes and/or of electrical arcing.Refer to Troubleshooting, "Ignition Secondary - Test".Electrical Connectors or Power Supply
There may be an intermittent interruption of power that is causing the symptom. Check the wiring harnesses and the connectors. Inspect the connectors in each of the junction boxes. Inspect the power supply connections and the ground connections.Inspect the wiring from the power supply to the Electronic Control Modules (ECM). Refer to Troubleshooting, "Electrical Power Supply - Test" for information that is related to the wiring harnesses and connectors.Ignition System
Inspect the ignition transformers for the following conditions: loose connections, moisture, short circuits and open circuits. Inspect the primary wiring and the secondary electrical connections.Ensure that the correct transformers and spark plugs are installed on the engine. Inspect the extenders for signs of pin holes and of electrical arcing. Check the spark plugs for fouling, correct gap adjustment, and moisture.Maintain the spark plug according to the engine Operation and Maintenance Manual.Incorrect Base Timing
Verify that the base timing is correct. Refer to Systems Operation/Testing and Adjusting, "Ignition Timing - Adjust".Fuel Supply
Use Cat ET to check that the engine fuel parameters are correct for the fuel that is being used. If necessary, perform fuel analysis in order to confirm the fuel quality.Verify that the fuel pressure is correct. When possible, interview the operator in order to determine if fuel quality is in question. Try to determine if the source of the fuel has been changed.Ensure that fuel is supplied at a sufficient pressure that is stable. Check that the size of the fuel line is sufficient. Inspect the fuel system for leaks.The following conditions can affect engine starting:
Low fuel pressure
High fuel pressure
Poor fuel qualityInspect the following fuel system components:
Fuel filter
Gas pressure regulator
Gas shutoff valve
Fuel metering valveVerify that the system components are operating correctly.Repair suspect components. Replace the fuel filter, if necessary.Inspect the fuel system for debris or moisture buildup. Repair and/or replace as necessary.Incorrect Air/Fuel Ratio
An air/fuel mixture that is too rich or too lean will have an adverse effect on engine operation. Verify that