A Crankshaft Sensor is an integral part of internal combustion engine of all the modern day vehicles. Used in co-ordination with the camshaft sensor, the Crankshaft Sensor monitors the pistons and valves behaviour in the engine. This electronic car part enables the engine control unit (ECU) of your car to control the timing of the ignition system by telling it when to inject the fuel.
Before crankshaft sensors came into existence, their role was played by a distributor installed in the vehicle and it used to be manually adjusted to a timing mark on the engine. The crankshaft sensor gathers very important information for engines with variable valve timing, as it monitors the rotational speed of the crankshaft. This data is ultimately used by ECU and other car parts for performing a lot of important functions.
A crucial component of fuel delivery system of all the contemporary vehicle engines, the crankshaft sensor is the key source for measurement of engine speed calculated in revolutions per minute (RPM). It features a toothed disc on a shaft and a fixed detector. As you turn the ignition keys of your car to “ON” mode, teeth on the disc start rotating by the stationary detector and in turn generate a pulse. This pulse rate is directly proportional to RPM, that is, the faster the engine runs, and the higher the pulse rate becomes.
The crankshaft sensor is usually located in the timing cover or on the side of the block with a cylindrical portion that inserts into the block. There are mainly four types of crankshaft sensors: Magnetic pickup coil sensor, Hall-effect sensor, Magneto-resistive element sensor, and an optical sensor. While the Magnetic pickup coil sensor, Hall-effect sensor and Magneto employ metal teeth on a wheel for creating the pulse signals for the ECM to read, the Optical position sensor makes use of an LED light and a photodiode to see the marks on the disk. Although, the Optical crankshaft sensors are more accurate, they require a lot of maintenance. Upon catching dirt, they are bound to give inaccurate reading, causing an incorrect air-to-fuel mixture, and ultimately affecting the proper functioning of your vehicle. That is the reason, these type of crankshaft sensor do not find place in a passenger car engine.
Just like other car parts, the crankshaft sensor is also liable to get burnt or worn out along with time. High heat levels are the primary factor that result in Crankshaft Sensor malfunctioning. A car engine refusing to start when it is hot, and starting-up upon getting cooled down, is generally the first sign of a faulty crankshaft sensor. Other symptoms of a faulty crankshaft sensor include cylinder(s) misfiring, loss of acceleration, difficulty in getting the vehicle’s engine started or it may not start at all. Engine vibrations, backfiring, stalling and irregular engine workings such as speed fluctuations, irregular acceleration and idling fluctuations may also indicate that the crankshaft sensor in your car needs attention.
If the crankshaft sensor starts malfunctioning while you are driving your vehicle, the ECM will go into “limp home” mode, in order to allow you to get to home or to the nearest mechanic. However, once the vehicle’s ignition has been turned off, it may not start until the crankshaft sensor has been replaced with a new one.
To determine how long the injectors should remain open, ECM in your automobile needs the information about speed of the engine, which is made possible by the crankshaft sensor. As the speed of the engine increases, the ECM knows that it must supply more fuel and air to the cylinders. More fuel gets dumped into the cylinders as long as the injectors stay open. Therefore, fuel consumption efficiency and your fuel expenses depend a lot upon the proper functioning of crankshaft sensor. Often a vehicle has only a crankshaft sensor, but some manufacturers use a camshaft sensor or a combination of both.