SPACER 2H9444 - Caterpillar

Timing Considerations
Once the governor has determined the amount of fuel that is required, the software must determine the timing of the fuel injection. Fuel injection timing is determined by the ECM after considering input from the following components:
Engine coolant temperature sensor
The sensor for the intake manifold air temperature
The sensor for the intake manifold pressureAt start-up, the ECM determines the top center position of the number 1 cylinder from the secondary speed/timing sensor in the fuel injection pump. The ECM decides when fuel injection should occur relative to the top center position. The ECM optimizes engine performance by control of the electronic unit injectors so that the required amount of fuel is injected at the precise point of the engine cycle. The electronic unit injectors are supplied high-pressure fuel from the fuel injection pump. The ECM also provides the signal to the solenoid in the fuel injection pump. The solenoid in the fuel injection pump controls a valve in the fuel injection pump. This valve controls the pressure in the fuel injection pump. Fuel that is not required for the engine is diverted away from the fuel injection pump back to the fuel tank.The ECM adjusts injection timing and fuel pressure for the best engine performance, the best fuel economy, and the best control of exhaust emissions. The actual timing can be viewed with an electronic service tool. Also, the desired timing can be viewed with an electronic service tool.Fuel Injection
The personality module software inside the ECM sets certain limits on the amount of fuel that can be injected.The FRC Limit is a limit that is based on intake manifold air pressure and engine rpm. The FRC Limit is used to control the air/fuel ratio in order to control the engine exhaust emissions. When the ECM senses a higher intake manifold air pressure, the ECM increases the FRC Limit. A higher intake manifold air pressure indicates that there is more air in the cylinder. When the ECM increases the FRC Limit, the ECM allows more fuel into the cylinder.The Rated Fuel Limit is a limit that is based on the power rating of the engine and on the engine rpm. The Rated Fuel Limit enables the engine power and torque outputs to conform to the power and torque curves of a specific engine model.These limits are in the personality module and these limits cannot be changed.Low Battery Voltage Elevated Idle (If equipped)
The low idle speed of the engine can be increased to approximately 1100 rpm if all the following conditions are met:
"Low battery voltage elevated idle" is enabled in the ECM.
Battery voltage is less than 12.25 VDC.
The engine has been operating at low idle for 5 minutes.
The machine is in neutral gear.
The parking brake is in the ON position.Diagnostic Codes
When the ECM detects an electronic system problem, the ECM generates a diagnostic code. Also, the ECM logs the diagnostic code in order to indicate the time of occurrence. The ECM also logs the number of occurrences of the problem.