Diesel Electronic Control

In the past, diesel engines earned a reputation for being loud and dirty. Moreover, light-duty diesels in automotive applications were considered slow, loud, and dirty. Highly reliable electronic fuel control systems have made today’s diesel engines fast, quiet, and clean. In fact, today’s diesel engines are more efficient than ever. Basically, an electronically controlled fuel system that consists of a computer receives information from various input devices, makes decisions, and directs the action of output devices. That is, it controls the exact amount of fuel injected into the combustion chamber. The computer or electronic control unit (ECU) is capable of making fuel metering decisions in microseconds. Another name that is used for the computer is power train control module (PCM). Other names and acronyms are also used depending on the manufacturer and the function of the computer.

Input devices include sensors and switches that provide the information necessary for the computer to make accurate fuel control decisions. Examples of input devices are throttle position, ambient temperature, engine coolant temperature, rpm, vehicle speed, and transmission gear. Other inputs monitored include crankshaft position, brake and clutch operation, battery voltage, cruise control request, and temperatures of oil, fuel, and exhaust. Additionally, intake air, oil, and fuel pressures are monitored. These devices can be variable resistors, switches, or transducers. They may range from very simple to complex electrical and electronic circuits.

The most obvious output device is the fuel injector, which is often operated by an attached solenoid. Other output devices could include the glow plugs, cooling fan, idle control, air conditioner, and warning devices. Often, output devices are electric motors and solenoids. Additionally, the computer monitors the fuel and emissions for OBDII and sets diagnostic codes when necessary.