0325639 JOHNSON CYLINDER HEAD, Star 235

Recommended Repairs
Fuel Supply
Make sure that fuel is supplied at a sufficient pressure that is stable. Make sure that the size of the fuel line is sufficient. Inspect the fuel system for leaks.The following conditions can cause the engine to malfunction:
Low fuel pressure
High fuel pressure
Poor fuel qualityMake sure 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 was changed.Inspect the fuel system components: fuel filter, gas pressure regulator, gas shutoff valve and fuel metering valve. Verify that the system's components are operating correctly.Replace the fuel filter, if necessary.Electrical Connectors or Power Supply
There may be an intermittent interruption of power. Check the wiring harnesses and the connectors. Inspect the connectors in the terminal box. Inspect the power supply connections and the ground.Inspect the wiring from the power supply to the master Electronic Control Module (ECM) and to the slave ECM. Check the power and ground connections. Refer to Troubleshooting, "Electrical Power Supply - Test".No Signal from the Engine Speed/Timing Sensor
Make sure that the engine speed/timing sensor is installed correctly. Refer to Troubleshooting, "Speed/Timing - Test".Make sure that the timing wheel is correctly installed.Ignition System
Significant improvements have been made to the parts in the ignition system in order to reduce losses in the ignition system. Ensure that current parts are used for the following components:
transformers
extenders
spark plugsInspect the ignition system for the following conditions:
Check the connection between the ignition transformer and the extender. A loose connection can cause arcing and misfires.
Check the connection between the extender and the spark plug for a loose connection or for pin holes that are caused by arcing. Both conditions can cause misfires.
Check the extender for corrosion on the spring. Corrosion may cause arcing through the extender.
Check for corrosion on the terminal of the spark plug and check for wear on the electrode. Both conditions can cause misfires. Other losses or misfires can be caused by shorts or excessive moisture.Maintain the spark plug according to the engine's Operation and Maintenance Manual.Check the Base Timing
Verify that the base timing is correct. Refer to Systems Operation/Testing and Adjusting, "Ignition Timing - Adjust".Excessive Load
Make sure that the load is not excessive. Reduce the load. If necessary, disengage the driven equipment and test the engine.Noisy Ignition Transformer
A transformer that creates electrical noise can cause communication errors between the electronic control modules. When this occurs, a 254-9 Electronic Control Module : Abnormal Update Rate will be generated.
590-09 Electronic Control Module : Abnormal Update Rate
1636-09 (Slave) Engine #2 Electronic Control Module : Abnormal Update RateThese codes are usually accompanied by a diagnostic code for the engine speed/timing sensor. The engine will shut down. When the engine is shut down, you can clear the codes.The problem is a noisy transformer if the codes recur on a subsequent attempt to start the engine. Perform the following procedure in order to identify the noisy transformer:
Clear all diagnostic codes.
Record the values of the "Engine Purge Cycle Time" and the "Cycle Crank Time" parameters.
Set the "Engine Purge Cycle Time" to 25 seconds. Set the "Cycle Crank Time" to 35 seconds.
Crank the engine. The engine will crank through the purge cycle. When the purge cycle time is complete, the ignition will turn on and the "communication" diagnostic codes will be generated. The engine will not start.
Turn the gas supply OFF.
Set the "Engine Purge Cycle Time" to zero seconds.
Disconnect the connector for an ignition transformer. Note: An "open circuit" diagnostic code will be generated for each transformer that is disconnected. Ignore these codes. Clear the codes when this procedure is complete.
Crank the engine. If the "communication" codes recur, connect the transformer. Disconnect a different transformer and crank the engine again. When the noisy transformer is disconnected, the engine will crank through the crank cycle. The "communication" codes will not occur.
Replace the noisy transformer.
Crank the engine after the new transformer is installed. Verify that the new transformer does not cause a "communication" code.
Clear all diagnostic codes. Set the "Engine Purge Cycle Time" and "Cycle Crank Time" parameters to the original values.
Turn the gas supply ON. Return the engine to service.