List of Sensors That Are Used on EFI Engines

by David Karanja
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engine image by Tomasz Pawlowski from

Electronic fuel injection (EFI), the most widely used fuel system today, utilizes a computer to inject fuel into the engine. This computer checks for changes in sensor inputs after each millisecond and is designed to change the pulse if anything changes. EFI technology needs many different types of sensors to work properly. Each of these sensors has to perform perfectly to ensure that the engine works well.

Temperature Sensors

Air temperature sensors are mounted near the air filter. When the temperature of the air gets colder, an increase occurs in its density and more fuel is required. Now the computer can effectively reduce the pulse width to make up for the high density.

Water Sensors

Water temperature sensors are needed to make the engine start and warm up properly. A cold engine needs a rich air-to-fuel ratio for its starting process. The computer increases the pulse width for extra fuel and can also reduce it when the temperature of the water increases. When the water is warmer than 120 degrees, no more extra fuel is needed and the computer has done its job.

Pressure Sensors

Manifold pressure sensors are made to measure changes in manifold pressure that occur because of changes in speed and load of the engine. These input sensors are important for calculating airflow. When the throttle is open, manifold pressure will increase and the engine will need more fuel.

Airflow Sensors

This type of sensor can detect the air mass that enters the engine. It is considered to be a primary input signal. A certain amount of fuel needs a certain amount of air. When throttle opening and rpm increase, airflow does the same.

Throttle Position Sensors

Throttle position sensors are required for acceleration when the throttle is opened rapidly. The computer knows how the throttle angle moves and how quickly it opens, so it can supply fuel momentarily when it is needed. There is a potentiometer on the throttle shaft that measures the position. This works like an accelerator on the carburetor.

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