How to cheat the fuel level sensor and why it may be necessary

Why cheat the fuel level sensor and how to do it

Every conscious motorist is well aware that the fuel level sensor is a very useful and sometimes necessary element of a modern vehicle.

Fuel level sensor

Not everyone understands why suddenly someone may need to cheat this controller. After all, when using a car, the driver needs to understand how much fuel he has left in the tanks, intelligently calculating the speed and distance he can travel on the available fuel.

For yourself, when the car is fueled at your own expense, there is no sense in cheating the gauge. This is more common among drivers of trucks and trucks owned by companies. After all, reselling fuel by draining it is one way to make extra money.

Ways to protect against fuel dumping

To prevent unscrupulous drivers from draining, reselling and demanding compensation for the used fuel by deceiving the employer, the latter use various methods of protection against such tricks.

Most often this is done by:

  • sealing the tank;
  • fuel coupons;
  • level gauges.

Sealing a car tank

Coupons are a measure of protection against counterfeit receipts, with which drivers then demand financial compensation. But it in no way protects against fuel drainage and resale.

With sealing, the previous method of fraud is eliminated. But it is difficult to implement, because the company is required to have its own gas station.

Sensors eliminate the disadvantages of the previous two methods. But in practice, even they can be cheated. There are several methods for this purpose.

The sensors used

Before talking about how to cheat the fuel level sensor in the tank, it is necessary to get acquainted with the controllers themselves.

All the sensors used can be divided into 2 categories.

  • Mechanical. This is a kind of tube with a float, which is immersed inside the fuel tank. Such sensor is characterized by a large error, which is why it is used less and less often in recent years.
  • Electronic. They are also located inside the tank. But their peculiarity of work is to measure the dielectric permeability of fuel. This value changes depending on how much fuel is in the tank.

None of the sensors can guarantee 100% accuracy of measurement. And often the error is not caused by the sensor itself and is not related to the manipulation of the driver.

One of the main reasons why the sensor cannot work accurately is the poor quality of fuel.

In fuel, especially in diesel, which is more often used in trucks, there are a lot of impurities, and the quality differs markedly from the declared and regulated.

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The impurities accumulate on the surface of the sensor. Because of this, the float of mechanical controllers soon begins to jam, and in electronic devices the measuring electrode becomes contaminated. This has a negative effect on measurement accuracy. To avoid surges and dips in the fuel consumption graph, the controllers should be periodically cleaned. But in practice it is difficult to do this, because the sensors are located in hard-to-reach places.

Fuel level sensor in a tank

Ways to cheat sensors

There are several ways you can intentionally cheat the fuel level sensor. The most common way to do this is by:

  • mechanical damage;
  • Draining at an incline;
  • draining through the return system;
  • changing the dielectric constant.

Each option is worth talking about separately.

Mechanical Damage

The driver, who does not want his employer to be able to control the volume of fuel consumed, goes to different tricks.

The simplest one is banal mechanical damage of the controlling sensor. In this case, the driver removes the responsibility for the serviceability of the device. But in case of its failure or incorrect work, no one will know how much fuel he actually used, and how much he poured or sold.

There are several ways to achieve damage to the sensor:

  • jumping on the fuel tank, hitting the outside of the housing;
  • pour boiling water on the electronic sensor;
  • short-circuit the controller with a high-capacity capacitor, etc.

As a result, the owner of the car has to spend additional time and money on the sensor replacement.

If such a situation arises, and if it happens again, the employer’s confidence that the employee is cheating and fraudulent is only growing. Then you have to part with the careless driver, look for his replacement and hope that the new employee will not do the same thing.

Fuel injection system with feedback

The fuel return system

There is one more interesting way to bypass the fuel level sensor installed in the tank. Drivers use the capabilities of the fuel return system to fool the control sensor and bypass it to their advantage.

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This is the easiest way to steal fuel. To do this, you just have to tap into the reverse drain system.

In older cars, the process of draining unused fuel is based on the principle of gravity.

Therefore, to cheat the sensor in such a situation is extremely simple. It is necessary to remove this fluid return flow pipe, and place it in a separate canister. As practice shows, when passing about 100 km. way it is possible to drain about 5 liters of diesel.

But modern cars are equipped with a changed system of return flow. Now the fuel which is not used at once remains under high pressure. As a result, any attempt to use the old method will fail.

There have been observed cases in practice of fleet owners, when an unscrupulous driver used a tee-connector embedded into the system of return flow.

That is, even modern systems can be cheated if you want to.

The car is tilted

Drivers who want to earn extra money cheat their employers. Sometimes to fool the installed FLS, it is enough to set your car on an elevation or park it on a slope.

Driving over a curb or other hill, the fuel in the tank shifts in the opposite direction from the sensor. Because of this, the controller fixes the level, which is lower than the real one.

As a result, using this method you can drain about 20 liters per one trip to the gas station, sell the fuel and put the earned money into your own pocket.

As soon as you drive the car off the curb, the sensor will increase the fuel level again.

The quality of Russian roads, and not only Russian roads, is quite low. As a result, cars constantly encounter potholes, potholes, etc. The car fluctuates, the sensor constantly registers different values, as fuel splashes in the tank from one side to the other. Because of this, employers often write off drained fuel on trivial error in the work of the controller. So here the bad roads, strange as it may seem, play into the hands of the drivers.

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Another trick, based on the principle of the electronic level sensor.

It is possible to change the dielectric permittivity by adding different liquids to the fuel. In particular, alcohol is used.

The controller is configured to work with clean diesel fuel. The driver only has to switch off the truck, drain about 50-60 liters and add a liter and a half of alcohol. Mixing it, alcohol and diesel leave the same dielectric value, as with a full tank of pure diesel.

Yes, sometimes you have to cheat not from a good life. Difficult work, low salaries force to cheat, leak fuel and earn money.

After reading this article, some will learn how to do it, and others will make conclusions to protect themselves from fuel dumping.

Cheating on fuel monitoring and control: top 10 “great” scams

The introduction of monitoring systems in commercial vehicles is now becoming an industry standard. And this is understandable – against the background of ever-increasing prices for fuels and lubricants and decreasing margins of the logistics business, a precise control of fuel consumption and suppression of fuel fraud become an important tool for reducing costs and increasing profitability of the company. In addition, the installation of a monitoring system allows you to control the movement of transport and transported cargo, which increases the safety of transportation and efficiency of the company as a whole.

However as any innovation the introduction of monitoring systems often faces opposition of common employees of the company, who together with introduction of control lose the possibility of fuel leakage and “left” earnings by using vehicles in their interests. In their turn, the drivers are worthy successors of Kulibin who do not give up trying to put the equipment out of operation and invent the most incredible means and methods.

About what tricks drivers fall for and how they can be discovered by told Dmitry Zhuravlev, CEO of Omnicomm-Service, a company specializing in the implementation and maintenance of transport monitoring and fuel consumption control systems Omnicomm. “Unfortunately, the Soviet idea is still alive in many drivers,” he said, “that ‘everything around is kolkhoz – everything around is mine.’ So they believe that they can dispose of the fuel and vehicles allocated to them as they see fit, and the introduction of controls deprives them of their ‘legitimate’ earnings.” I can tell you about the ten most popular and unusual ways in which vehicle monitoring and fuel monitoring systems break down, and exactly how to detect these diversions. I am sure this information will help the management of logistics companies to catch drivers-vandals.

How to protect your car from theft

Method 1: Irregular return (cavity) draining

How to do it: a nipple (tee) is inserted into the fuel return line (return) and the fuel is drained through a hidden hose.

How to spot a failure: The monitoring system automatically detects an increased flow rate and signals it. Subsequently, the task of the mechanic is to find artfully hidden fittings, canisters, cavities – where and how the fuel is drained. In this picture you can see that the fuel is poured into a neatly made container directly in the cavities of the working mechanisms of the special equipment.


The tank is in the working cavities of the tractor




Nozzle on the return

Method 2: Regular draining of return flow (within limits)

How to do it: small diameter hose is inserted into return fuel line and connected to canister without disconnecting the line itself.

How to determine the failure: the monitoring system automatically registers an increased flow rate, however, it is slightly higher than the norms of this type of equipment. The task of the mechanic – to determine the causes of increased consumption by visual inspection and find skillfully hidden fittings, canisters, cavities – where and how the fuel drains.


Method 3: pour boiling water or burn fuel level sensor

How to do it: pour boiling water on the fuel level sensor or burn it with a blowtorch.

How to spot a failure: after baking with a blowtorch the gauge stops working and visual inspection shows damage. Boiling does not affect the sensor reading.


Method 4: Burn the wires

How to do it: the connecting cables are leaned against the exhaust pipe/burned with an open flame.

How to determine failure: visual inspection finds damage.


Method 5: pour acid or apply solidol to the connectors

How to do it: electrolyte or hydrochloric acid is injected into the connectors or wires of the fuel level sensor or the terminal itself, or grease is applied to the connector.

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How to determine and remove the failure: the failure will be visible visually and in most cases, cleaning and purging the contacts will be sufficient.Sealing the sensor wire connectors is done against unauthorized tampering.


Method 6: stick needles in the wires

How to do it: the fuel level sensor cables are pierced with a needle, thereby shorting the internal circuits of the equipment.

How to detect and remove the failure: the failure will be visible visually and it will be necessary to dismantle the faulty part of the cable.


Method 7: Taser/high voltage directly on equipment circuits

How to do it: a discharge is applied to the inputs of the equipment.

How to determine the failure: burn out the equipment’s internal protection circuits, designed for voltage shocks up to 2500V.


Method 8: bake in a microwave oven

How to do failure: the GLONASS/GPS terminal is left in a microwave oven for 30 seconds.

How to determine failure: low-cost terminals are made in plastic cases, after heating leave traces of melting of the case and explosion of capacitors. Omnicomm Profi terminal is made in a metal case and will simply cause microwave oven failure.


Method 9: change the volume of the fuel tank with a heater

How to do failure: at refueling place an inflated heating pad in the fuel tank.

How to spot the failure: you see increased flow when driving, and when you remove the heating pad, the software signals a drain.


Method 10: change fuel viscosity

How to do failure: dilute fuel with water, gas condensate or heating oil.

How to determine the failure: unstable operation of the engine, difficult starting, smoking, in winter – freezing of the sensor in the ice (sediment).


In conclusion I would like to note that almost all variants of failure of fuel monitoring and control equipment are vandalism and initial diagnostics reveals this fact and all attempts to cheat the system and sensors end with punishment. As for warranty cases of failure, usually their number is minimal, because the quality and competently assembled equipment works long and without failures.

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