The constant presence of a small canister of gasoline in the car or the car owner voting on the highway with a request to refuel, all this is a consequence of the fact that the fuel sensor in the car does not work. The breakdown of this sensor does not affect the operation of the main mechanisms of the iron horse, but it significantly affects the comfort of using the car, since there is always a need to calculate how much the car has traveled since the last refueling and how many more kilometers can be driven without stopping at a gas station.
Author of the article: mudriy_lev Specialization: repair of auto generators and servos in cars. Place of work: service center. Experience: 2 years. Education: higher education - electrical engineer, secondary specialized education - mechanical assembly mechanic.
Let's look at the main reasons.
Potentiometer and its problems
Modern cars are equipped with a wide variety of fuel level sensors. The widest niche has been occupied by sensors based on potentiometers. This type of conversion of fuel level information into an electrical signal has many advantages. There are two types of sensors based on this method of measuring fuel level:
- lever (widespread)
- tubular (used mainly on large vehicles)
If the lever-type fuel level sensor does not indicate the fuel level correctly, the reason associated with the potentiometer and causing this malfunction may be as follows:
- Potentiometer contacts have oxidized
- there has been natural wear on the tracks or slider of the resistor
- natural aging of the resistor
- resistor does not match the nominal value
Potentiometer Diagnosis and Troubleshooting
A symptom that the potentiometer contacts have oxidized is a temporary lack of accurate information about the fuel level in the gas tank. The owner notices that from time to time the indicator shows reliable information. Usually, in this case, the light indicating the end of fuel works flawlessly.
To diagnose this malfunction, it is necessary to visually inspect the variable resistor of the fuel level sensor. The oxides will appear different from the normal color. Based on their number, a decision is made on what to do next:
- clean (in case of a small amount of oxides)
- move the slider (if only part of the tracks are oxidized)
- replace the fuel level sensor with a new one (if the oxides are significant and have led to damage to the tracks or slider)
A symptom of natural wear of the tracks and runner is either a complete failure of the sensor, or its correct operation only in certain areas. A visual inspection in this case shows that the tracks are worn out, and in more rare cases, damage to the runner.
If it is possible to move (bend) the slider to an undamaged area, the sensor will please the owner with its long-term, proper operation. But if the runner is damaged, or the tracks are seriously damaged, repairs do not make sense. It is necessary to purchase a new fuel level sensor.
To establish the next reason why the fuel sensor does not work, you need a multimeter or an ohmmeter of any design. A resistor can change its resistance and, as a result, display unreliable information. Checking the resistance value with an empty, full and half-filled gas tank will help identify this problem. Repair in this case is not advisable, since it is safer to install a new sensor.
If problems with inaccurate fuel level arose after installing a new sensor, then a common cause is a resistance mismatch with the nominal value. This situation arises due to the fact that the sensors are similar in appearance, but their different modifications have different resistance values.
