The fuel tank pressure (FTP) sensor is a vital evaporative emission control system (EVAP). The EVAP system traps unburnt fuel vapor from the gas tank and transports it back to the fuel system.
This offers a high fuel economy, minimizes environmental pollution, and prevents premature engine damage. What is a fuel tank pressure sensor, anyway?
The FTP sensor is normally placed on top or inside the gas tank. Its primary function is to detect the pressure in the fuel system and enhance fuel economy.
If it fails, it’ll decrease the amount of gas in the combustion chamber. This can cause engine stalling, weak acceleration, bad gas mileage, and hard starting.
In this article, we’ll discuss what causes a fuel tank pressure sensor to go bad. And how to test a fuel tank pressure sensor. We’ll also outline the symptoms of a bad fuel tank pressure sensor and answer related questions.
What is a fuel tank pressure sensor?
As its name suggests, this part is a pressure sensor for your fuel tank. Why is it important to know what the pressure inside your fuel tank is? There are a few important reasons:
- To identify leaks in the fuel system
- To alert you to a defective gas cap
- To signal the engine computer that the evaporative emissions system is operating properly
- To regulate the management of fuel consumption
- To maintain compliance with state and federal emissions regulations
The fuel tank pressure sensor does all this by monitoring the pressure, both positive and negative, inside your fuel tank. This sensor is an integral part of your car’s evaporative emissions system, also known as EVAP.
The EVAP system is designed to keep all gasoline vapors within your car’s fuel system, after you have fueled it up at the gas station.
What Does The Fuel Tank Pressure Sensor Do?
The fuel tank pressure (FTP) sensor is part of the evaporative emissions or EVAP system. It monitors pressure to detect evaporative leaks and loose/faulty gas caps that may be preventing fuel vapors from being contained in the EVAP system.
Such leaks may result in decreased fuel efficiency, an increase in emissions, and decreased engine performance.
The process of detecting leaks starts with the FTP sensor monitoring the rate with which vacuum increases in the EVAP system.
Then the monitor uses this information to determine the purge volume flow rate. The EVAP monitor closes the purge valve, which creates a closed system. The FTP sensor then monitors the leak-down rate.
If the rate exceeds the stored value in the PCM consecutively, the powertrain control module sets a diagnostic trouble code (DTC).
Symptoms Of A Bad Fuel Tank Pressure Sensor
Calm your nerves when you’re wondering, ‘what happens when a fuel pressure sensor goes bad?’ Yes, there is good and bad news to expect. The awesome news is there are chances your car will run pretty fine. It may not affect your car performance in any way.
The sad news is that the vehicle will fail the emission test when the FTP sensor malfunctions. Of course, the engine warning light will appear on the dashboard.
And if you leave the light, thinking it appeared because of a bad FTP sensor, you won’t know when the car computer logs another issue, leading to catastrophic engine damage.
#1. Check Engine Light.
If you see the engine warning light illuminate on your dashboard, then it could be a sign that your fuel pressure sensor is bad.
Sometimes the engine control unit will sense a problem with the signal from the fuel rail sensor. Then it will activate the check engine light to let you know there is some kind of problem that is related to the engine.
Of course, there are a large number of other reasons for why the check engine light would turn on besides having a bad fuel pressure sensor.
#2. Low Power.
If you step on the gas pedal and notice a lack of acceleration, then it could be due to the fuel pressure sensor. If the sensor is bad, then it will interfere with the air and fuel ratio. This will cause a noticeable loss of power from your vehicle as you’re driving.
#3. Problems Starting.
If you try to start your vehicle’s engine and it doesn’t start on the first attempt, then your fuel pressure sensor may not sending a good signal to the engine’s computer or something is causing low fuel pressure.
At first, the engine will eventually start after cranking a few times. But eventually, it may get to the point when it doesn’t start at all.
#4. Stalling.
Sometimes you might get a not-so-nice surprise and have your vehicle stall as you’re driving it. If you previously had trouble starting your car but then got the engine to finally run, you may experience stalling as you’re driving later on.
But even if it is the first time the car has stalled, it could still be due to a faulty fuel pressure sensor.
#5. Bad Fuel Economy.
With a bad fuel pressure sensor, the engine will not receive the correct amount of fuel for its internal combustion process.
Most of the time, too much fuel will be pumped into the combustion chamber and there will be a noticeable reduction in your MPG from running too rich.
Larger vehicles such as a Chevy Silverado and its 6.6L Duramax engine will have more noticeable effects than something like a 4-cylinder Toyota Corolla engine.
#6. Rough Idling.
You may experience rough idling, misfires, and even the care shaking due to an incorrect fuel/air mixture. This is because the PCM is receiving inaccurate data from the sensor, causing it to adjust the fuel mixture inappropriately.
Rough idling can lead to increased wear on engine components and reduced overall performance (in addition to it being annoying and uncomfortable).
#7. Hesitation During Acceleration.
Due to an inconsistent fuel supply to the engine, a vehicle with a bad fuel pressure sensor may hesitate or stumble before gaining speed.
When you press the accelerator, the PCM expects a certain increase in fuel pressure. However, if the sensor is not providing accurate data, the PCM may not adjust the fuel mixture correctly, resulting in a delay in acceleration.
This can be particularly noticeable (and dangerous) when merging onto highways or passing other vehicles.
#8. Fuel Smell.
If the fuel pressure sensor is causing the engine to run rich (too much fuel), you may notice a strong fuel smell from the exhaust or around the vehicle.
This again occurs because of incorrect data from the sensor being communicated to the PCM, leading it to inject more fuel than necessary into the combustion chambers.
This excess fuel does not burn completely, resulting in unburned fuel (sometimes in the form of dark smoke) being released through the exhaust system.
#9. Engine Surging.
A malfunctioning fuel pressure sensor can cause the engine to surge or suddenly increase in RPMs while driving at a steady speed. Again, this is due to incorrect data being interpreted by the PCM.
As a result, the engine may receive an unexpected surge of fuel, causing it to briefly accelerate without driver input. This can be disconcerting and a huge safety issue as it will be more difficult to maintain a consistent speed.
What causes the fuel tank pressure sensor to fail?
There are a number of reasons why your fuel tank pressure sensor may be wearing out or becoming damaged, including:
- Extreme temperatures, poor weather conditions, rough roads, or persistent exposure to fuel vapors can wear down the sensor over time.
- If you fill your fuel tank too much, the excess fuel can spill into the charcoal canister and other lines, potentially damaging the sensor.
- If the sensor isn’t installed or maintained correctly, it might not work right or could break sooner than expected.
- Just like anything else in your car, the sensor can wear out over time from regular use and age.
- Dirt, debris or leftover fuel can clog the sensor, affecting its ability to perform its job properly.
How Do I Test A Fuel Tank Pressure Switch?
Checking the FTP sensor is pretty simple. It is a three-wired component that is quite easy to test. The three wires are a ground wire, a voltage wire that goes to the engine control module, and another wire that returns volts to the ECM.
So, if you suspect a bad FTP sensor, check these wires to know if the FTP switch is bad or if the problem is from somewhere else.
Unfortunately, you may have to drop the gas tank to access the FTP sensor because it is mounted on top or inside the gas tank.
For this reason, it is typically inaccessible for an average motorist, which explains why you need to consult your mechanic to check and replace the sensor.
However, here are a few ways to follow if you decide to check the FTP sensor yourself.
- Locate the sensor
- Unplug the wiring harness
- Connect your multimeter or voltmeter
- Compare the reading on the voltmeter and compare the specified signal on your manual. Ensure the readings are the same.
- Check the wiring harness and replace corroded or burnt wires.
How Do You Fix A Gas Tank Sensor?
If the test proves you have a defective FTP sensor, you may ask, can you drive with a bad tank pressure sensor?
As we explained earlier, a bad FTP sensor cannot affect the overall engine performance. It can also project several drivability issues and trigger engine check lights on the dashboard. For this reason, do not drive with a defective gas tank sensor.
So, what should you do, then?
Fix it before hitting the road. Unfortunately, the only recommendation to fix the FTP sensor is to replace it. The sensor is pretty inexpensive, but the replacement cost can be high depending on your fuel tank design.
FAQs.
Q: Can a bad fuel pressure sensor cause no start?
If you have a lousy FTP sensor, it can cause the fuel injectors to send an obscene amount of gas to the combustion chamber. This can lead to hard starting.
At first, it will only take a few attempts before turning on the vehicle. But as the case worsens, it’ll take several attempts before starting the vehicle.
If you keep ignoring it, it may get to a state where the engine will start and shut off. In rare situations, it may cause the engine not to start at all.
Q: Can a bad fuel pressure sensor cause a misfire?
Like fuel pressure regulators, the common sign of a bad FTP sensor is weak acceleration and engine misfire.
You’ll notice a sudden loss of engine power output when driving. The vehicle may stumble, hesitate, or even bog when taking an early morning ride or on a sunny afternoon.
The acceleration may become pretty fine in no time and suddenly fail again. This can be dangerous. Therefore, do not drive with a bad FTP sensor if it gives sudden changes in the accelerations.
Q: How long does a fuel tank pressure sensor last?
Automakers design FTP sensors to last the vehicle’s lifespan like most car sensors and switches.
However, the sensor can break when working on the fuel tank because of its location. A mechanic may mistakenly break it when working on the gas tank. It can also wear on the terminals and damage.
Q: How much is a fuel tank pressure sensor?
The average replacement cost for an FTP sensor is $250 to $325. The parts should be around $50 to $75, while the labor charge is around $200 to $250.
This is a general replacement estimation. It doesn’t deal with any specific vehicle make or model. Other factors, like taxes, location, and related repairs, may increase or reduce the replacement cost.
Q: Can you clean a fuel pressure sensor?
Of course, you can clean a fuel pressure sensor, but there are huge chances that it won’t make any difference.
Because of the location of the sensor, dirt can clog the terminals and prevent them from sending accurate signals to the car computer. If this is the case, cleaning will revive the sensor. However, in most cases, the only option is to replace the sensor.
Q: Can you bypass a fuel tank pressure sensor?
Fuel tank pressure sensor bypass is a hit or miss repair. You can plug or bypass the pressure sensor. But once you bypass it, the check engine light will illuminate on the dashboard.
Final Words
The FTP sensor is one of those important components many motorists do not know in a car. However, the signal from this sensor offers a good fuel economy, saves you some cash, and enhances optimal engine performance.
Unfortunately, symptoms of a bad fuel tank pressure sensor can be mistaken for other system malfunctions.
Therefore, if you notice any of the outlined signs above, ensure you diagnose the vehicle with a scan tool. This will help you fix the culprit without doing guesswork.