Understanding Fuel Tank Related Parts

Fuel Tank Pressure Sensor, also called a fuel pressure sensor, scans the pressure in the fuel tank system and detects any leaks that are explicitly caused due to evaporation, alerting the vehicle’s electronic control units (ECU). The fuel tank pressure sensor is a part of the fuel assembly connected to the ECU and works with the vehicle’s evaporative emission system (EVAP). The fuel pressure sensor senses fuel tank and evaporative (EVAP) leaks, such as a loose or faulty gas cap, helping repair the leaks at the earliest. The data collected by the sensor transmits to the ECU, and the Check Engine Light on the dashboard indicates the traces of leaks in the evaporative emissions system or the sensor. The fuel tank pressure sensor allows vehicle owners to comply with federal and state regulations considering emissions from fuel systems and saving fuel and money.

The fuel tank pressure sensor is a crucial part of the EVAP (Evaporative Emissions Control Systems). The EVAP collects and reintroduces unburned gasoline vapours from the fuel tank into the fuel system. It helps by conserving fuel, reducing pollutants, and preventing engine damage. 

The fuel tank pressure sensor is critical for the engine's smooth operation via the Powertrain Control Module (PCM) and leak detection. A faulty fuel tank pressure sensor may show one or all of the symptoms mentioned below:

1. Poor Gas Mileage

If there is an unusual increase in gas consumption and the vehicle’s mileage goes down, it is a possible sign of a faulty fuel pressure sensor. The fuel pressure sensor is responsible for regulating engine fuel consumption. So when it malfunctions, excess fuel is supplied to the engine. This results in incomplete combustion which leaves behind unburned fuel and damages the engine due to the phenomena called knocking. Knocking is the detonation of the unburned fuel that causes a steep rise in pressure and temperature, thus damaging the engine.

2. Sluggish Acceleration

If the combustion process is incomplete then the required power is not generated and the vehicle struggles to accelerate. Thus, the vehicle will struggle to advance even when the required pressure is applied to the accelerators. This symptom might be an indication of a faulty fuel pressure sensor. When you have a malfunctioning fuel pressure sensor, your car's engine can get too much or too little gasoline, which lowers its performance. 

3. Startup Issues

The vehicle needs an optimum amount of fuel to start and if the fuel pressure sensor is faulty then its failure to detect the amount of fuel might cause a hindrance in the startup process. An ignition coil supplies electricity for spark plug ignition in S.I engines (Spark Ignition). The spark plug ignites the air-fuel combination at the end of the compression cycle in the ignition chamber. However, in the case of the CI engine (Compression Ignition), the combustion process occurs when the air-fuel mixture is compressed to auto-ignition temperatures. It won't start without the proper amount of fuel, whether a compression or spark ignition engine. 

4. Stalling

Stalling means you suddenly feel powerless while driving as the engine is unable to generate power during the power stroke during the combustion process. In a four-stroke engine, there are four key processes: intake, compression, power, and exhaust. Therefore, each process provides a power stroke, and if the fuel level is below the optimum level, you get low or no power during the power stroke. This low fuel situation arises due to the inability of the faulty fuel tank pressure sensor to sense the correct levels of the air-fuel mixture in the combustion chamber.

5. Engine Light on Dashboard

When the vehicle’s Check Engine Light (CEL) flashes, it could be a sign of a faulty fuel pressure sensor. Ignoring it when the automobile runs and drives normally may appear rational for a while, but issues of low acceleration, startup problems, and stalling will continue to arise. 

6. Unburned Fuel

When the fuel pressure sensor in your car fails, the piston receives additional fuel; some of this gasoline does not burn in the combustion chamber and is stuck in the exhaust system. This might be a sign of a faulty fuel pressure sensor. Overlooking this issue may have adverse effects on the efficiency of the engine leading to poor mileage.

Therefore, if any of these symptoms are observable, never ignore them as they can be a sign of a faulty or damaged fuel pressure sensor.

The fuel tank sending unit positioned inside the fuel tank is a potentiometer with a float connected to the rod that functions similar to the toilet bowl. It relays the information directly to the vehicle’s fuel gauge on the dashboard after measuring the amount of fuel in the tank. However, in the late-model vehicles, sending unit is usually attached to the fuel pump carrier bracket that contains the fuel pump. When the fuel level in the tank decreases, the arm with the attached float falls with it, changing the amount of the resistance in the potentiometer, indicating the fuel level inside the tank.

The fuel tank sending unit also called the fuel tank sender, has the primary function to let the driver know how much fuel is inside the fuel tank. If the fuel gauge reading indicates an empty fuel tank or the vehicle frequently runs out of fuel, it might be due to a faulty fuel tank sending unit. The fuel gauge often may indicate ‘full tank’ even though the vehicle has travelled a significant amount of distance. This issue can be caused due to a faulty insulation wiring, resulting in a short circuit or a faulty gauge or severed wiring between the gauge and the sender. Damage to mechanical components provides a fluctuating, non-changing, or utterly inaccurate reading, leading to the replacement of the fuel tank sending unit.

The fuel tank cap is a seal that is unscrewed to put the fuel in the car and put back when the fuelling is complete. Fuel tank caps prevent the leaking of the fuel vapours by trapping them inside the system. Cap enables the car to ensure safety, improve performance, and fuel efficiency, and reduce emissions. The fuel tank cap prevents water vapour from entering the fuel tank which can damage the tank. Since water is denser than fuel, it will not mix and eventually get deposited at the surface of the tank leading to rusting of the tank in the long run and eventually will affect the service life of the fuel tank. It also prevents pollution by stopping fuel vapours from seeping into the atmosphere. Automotive fuel contains various hydrocarbons and when these react with air and sunlight it creates smog. Gasoline evaporates very quickly, therefore, if the fuel system is exposed to the air it can continue polluting the environment all day without even being turned on.

The fuel tank cap also acts as a barrier between larger debris such as leaves, sticks, and pebbles and tiny debris such as dust and grime, protecting the gasoline tank and keeping the gas as clean and pure as possible. The cap deteriorates over time owing to unscrewing and screwing that can lead to vapours escaping through even the tiniest flaw in the cap. 

If the issue is not fixed, it will result in poor engine performance and bad fuel mileage, and the automobile will fail the emission test.

If you can see any of the below warning signs and symptoms, then it's time to get the vehicle's fuel tank cap replaced: 

1. Engine Warning Light / Gas Cap Warning Light 

Fuel vapours will escape the system if your fuel tank cap does not provide a full seal. The evaporative emission control system will detect this and realize something is wrong, triggering the engine warning lights. 

It can often be observed that the fuel tank cap isn't screwed properly or fuel tank cap doesn't fit into place, or it is loose or not holding. In any case, this may allow the vapours to escape and debris to enter the fuel tank which causes the engine to stall, and increases performance problems in the vehicle.

3. Car Cabin Smells Of Raw Gasoline 

If the fuel tank cap is damaged and not holding correctly, it can lead to fuel vapours escaping the tank and getting into the vehicle ventilation system. Therefore, leading to a raw gasoline smell inside the vehicle. 

The fuel tank vent valve, also called the venting valve, is a part of the Evaporative Emission Control (EVAP) system. The fuel tank vent valve's primary function is to prevent the fuel vapour from escaping into the atmosphere and controlling the flow of outside air in and out of the charcoal canister. The vent valve is also known as Canister Close Valve (CCV) in some vehicles. The charcoal canister is linked to one side of the vent valve, whereas the other end is connected to the vent hose with a filter or screen attached to the vehicle's body or frame. 

The fuel tank vent valve is usually open and only closes when the engine computer detects any leaks in the EVAP system. The Check Engine light appears on the dash if a leak is detected and logs the trouble code associated with the malfunction in the engine computer.

EVAP system includes a fuel tank vent valve, pressure switching valve, canister vent valve (solenoid), and purge valve (solenoid). These valves perform evaporative emission control functions from the fuel tank, collecting gas vapours in the charcoal canister and consuming the stored vapours in the engine for combustion. Both the fuel tank vent valve and the purge valve are part of the EVAP system. 

The fuel tank vent valve prevents liquid fuel from entering the charcoal canister in the event of vehicle toppling and also facilitates vapour movement to the charcoal canister. It is located on the top of the fuel tank, and sometimes it comes as in-built with the in-tank fuel pump module. 

The purge valve’s main job is to drag or purge the vapours gathered in the charcoal canister towards the intake manifold. The purge valve is located close to the engine manifold next to the throttle body or situated over the fuel tank sitting on the charcoal canister.