The gas cap’s purpose is to provide a reliable cover that stops dust, debris, and dirt from entering the gas tank. It plays a significant role in converting dangerous fuel vapor into harmless discharge in the car’s emissions system. Because you have to remove and replace your vehicle’s gas cap for every refueling session, the cap eventually wears out, and you may need to replace t after some time. Loose gas caps can lead to fuel leakage problems that bring about uncomfortable smells and worse hazardous risks to you and your car.
- This is because a rich fuel mixture is over-saturated with gas, causing ignition problems. Mixtures that have too much air and not enough fuel are lean and tend to reduce the amount of power available under load and can cause stalling. In both cases, a professional carburetor inspection and adjustment are necessary to correct the problem.
- Bad Fuel Gas will go stale in as few as 30 days, especially fuel mixed with ethanol as it is in many areas. Ethanol attracts moisture over time and the moisture will dilute the gas. Diluted gas may cause your engine to stall.
What are the symptoms of a bad gas cap? Here is a detailed list of problems associated with a failing gas cap.
Unclog or replace gas cap if air vent is blocked. Change air filter if it’s clogged or dirty. Prime engine if equipped with small rubber bulb. Replace fouled or dirty spark plug.
Symptoms of Bad Gas Cap
Because a faulty gas cap can lead to several mechanical problems, it is essential that you watch out for the following symptoms that mean you need to get a cap replacement.
Problems Tightening the Cap
The first and most apparent symptom of a failing gas cap is it develops tightening and fitting problems. Vehicle manufacturers design gas caps in such a way that they click once to let you know they correctly tightened. A damage cap cannot tighten until it makes a clicking sound. On occasion, the gas cap pops open even after tightening it.
These simple signs show you that it is high time you replace your gas cap.
Strange coloration at around your gas tank mouth
When you have strange discoloration or coloration around your gas tank door cover, you probably are dealing with a failing gas cap. Since the gas cap cannot seal the tank adequately, fuel fumes escape and deposit on the gas tank opening. These fumes progressively discolor the surfaces they come across. Therefore, you can easily diagnose a leaking gas cap by the deposited fuel residue inside your filler door gas tank cover.
Foul Gasoline Smell While Driving
Since your vehicle leaks fuel because your gas cap cannot seal the tank, you can expect to experience a foul fuel smell every time you are in the car. The escaping vapor not only makes your vehicle uncomfortable to use but is a severe health risk. Furthermore, petroleum is highly volatile and can ignite when triggered by any fire source.
Poor Fuel Economy
Apart from keeping the environment cleaner by protecting it from fuel fumes, the gas cap also saves you a lot of money by making the car fuel-efficient. A leaking or broken gas cap affects your fuel economy, crucially causing low mileage. If you don’t replace it, you can waste as much as 30 gallons of fuel within a year. If that is not enough, the leaking fumes cause worse greenhouse problems to the environment.
The Check Engine Light Comes On
Another symptom of a failing gas cap is the illumination of the check engine light. Since the gas cap is an essential part of the car’s emissions system, it can worsen the system’s efficiency if it has inadequate gas sealing. A gas cap that cannot seal can cause an EVAP system leak. The EVAP leak sets off the Check Engine Light.
Although a bad gas cap cannot cause loss of power and critical performance issues, it sets off the Check Engine Light. An illuminated check engine light will cause the car to fail an emissions test. Therefore, you need to take the car to the mechanics for inspection or purchase and replace the filler cap whenever you suspect it is malfunctioning.
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Symptoms of a Bad Gas Cap (FAQs)
Q: Can a Bad Gas Cap Cause Idle Problems?
Almost all fuel injected cars use pressurized fuel systems and depend on the gas cap to be tight enough to deliver the required pressure. Therefore, a loose or a failing gas cap will bring about idling problems because of insufficient fuel system pressure.
You can also have a rough idle from dirt and impurities that make their way into the gas tank’s neck because the gas cap cannot shut off correctly. These impurities alter the fuel injection pressure and clog or block the featured fuel delivery and cause rough idling.
Q: Can a Bad Gas Cap Cause Misfire?
A car misfires when the required fuel combustion does not occur. Insufficient combustion happens when your air to fuel ratio is not at the required levels. Damaged gas caps leak fuel outside the tank and pipes. They also allow impurities into the vehicle fuel system. However, they only affect the fuel-to-air ratio slightly.
Therefore, can a bad gas cap cause stalling and misfires? It can, but the most likely causes for vehicle misfires would be a malfunctioning air flow sensor, a bad fuel pump, spark plugs, and ignition problems, or electrical transmission issues.
Make sure you watch out for symptoms of these parts malfunctioning before you head to the repair shop to buy a new gas cap.
Q: Does a Bad Gas Cap Affect Mileage?
As mentioned earlier, one of the worst effects of driving with a faulty or absent gas cap is that you will lose a lot of fuel through spillage and gaseous emission. Your vehicle will be subject to poor fuel economic efficiency, which will lower the distance you can drive with a gallon of gas.
Using a vehicle with terrible mileage is not only financially uneconomical but puts you at the risk of abruptly getting stranded with an empty tank on the highway.
Q: What Codes Will a Bad Gas Cap Cause?
Several engine problems can set off the check engine light. However, when your car has a failing gas cap, it sets out a P0455 or a P0457 code to the car’s ECM. The codes mean that your vehicle has a massive leak or a loose gas cap problem.
The codes can also represent insufficient pressure in the fuel injection system due to the faulty gas cap.
Q: How Can I Test my Gas Cap?
Although most gas caps are attached to their car’s fuel cap door, there are times people forget to close their gas caps after they refueled their vehicles. When you drive the car from the gas station, the check engine light automatically comes on. Other car models fail to restart or run with difficulties. The check engine light indicates that the gas cap is missing, not sealed, or damaged.
How to fix a loose gas cap is a simple procedure. Open the fuel tank door by pushing a button in your glove compartment box or next to the seat. Physically open the tank door and check the cap carefully for physical damages. When there aren’t any damages, screw the gas cap to the tank and make sure it clicks to symbolize that it’s completely tightened.
Q: How Long Do Gas Caps Last?
Depending on your car model, the environmental conditions it is subjected to, and how well you take care of it, the gas cap can last you a mileage of more than 50,000 miles. However, since you screw and unscrew the caps frequently whenever you refuel, the filler caps require replacement after a while to avoid the previously mentioned problems.
Most small car parts’ lifespans are influenced by the salinity, temperature, and humidity of the vehicle’s environment.
Q: How To Check for Bad Gas Cap Leaks
Modern car’s Evaporation Emission Control Systems automatically run tests to detect gasoline vapor leakages from the EVAP and the gas tank system. The EVAP tests are responsible for the P0455 and P0457 codes sent to the computer to notify you of leaking gas.
However, these tests only run at specific times. They don’t run diagnostics when the fuel tank is less than 15% full or when it’s more than 85% full. Also, the self-test doesn’t run when there extremely cold or hot temperatures. Therefore, the vehicle will most likely run EVAP tests a long time after you parked your car.
If you received a bad gas cap code and closely inspect your gas cap, but you don’t find physical evidence of the leakages, it may mean your leakages are at the vapor HOSES. Start with asking yourself, how can I test gas cap pressure? You can use pressure testing to rule out leakages in deeper parts of the fuel system. Use needle and nose vise grips to seal the supply and outlets of the tank. Use a pressure tester to find out if there are any pressure changes after five minutes of clamping the reservoir’s inlet and outlet.
Alternatively, you can confirm leaks by using a smoke machine with low-pressure oil with colored dye. Pumping the EVAP system with this colored oil will help you identify the location of the leakages.
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Do I Need to Replace My Gas Cap? YouTube
Final Words
Apart from providing a top to the fuel tank, a vehicle gas cap performs many operations to ensure a car runs smoothly. A fuel cap maintains the fuel system vacuum pressure seal allowing the pump to feed fuel to the combustion system efficiently.
A fuel cap also seals deadly pollutants and fumes in the tank and protects the environment. The EVAP processes protect vehicle passengers and the environment from the negative effects of gasoline fumes.
Finally, the gas cap protects the gas tank contents from external impurities, dirt, and water during rainy weather. When you don’t have a clean gas tank because of debris or impurities, your vehicle will experience clogging, which spoils injection systems, the fuel filter, and the pump tank. These problems cause engine malfunction and diving difficulties.
We take gasoline for granted.
For most of us, it’s as simple as putting gas in, and thendriving away. These days, it’s very rare that you’ll get bad gas from a gasstation. In over 18 years as an auto mechanic, I’ve never seen someone’s enginedamaged by bad gas.
It just doesn’t happen as much as it used to.
But it does still happen.
Back in 2012, over 4.7 million gallons of gas were recalled from BP stations in Chicago, Northwest Indiana, and Milwaukee. The bad gas, in this case, was contaminated with polymer residue, which doesn’t burn in automotive engines and can cause damage to the engine.
Generally speaking, bad gas is usually the result of contaminationfrom your fuel tank or fuel line. It can be the result of your car sitting foran extended period of time, or from water making its way into the fuel tank.
By the time you’re finished reading this guide, you’ll be anexpert in diagnosing if your car actually has bad gas, as well as correctingthe problem if it becomes an issue.
You’ll learn everything you need to know – and probably somethings you don’t need to know.
What Causes Gas To Go Bad?
Gasoline doesn’t stay good forever. The countdown starts assoon as you expose gasoline to air. After around 30 days or so of sitting inyour fuel system, your gasoline starts to oxidize.
When gasoline oxidizes it can gunk up your fuel system by turninginto varnish which can coat your fuel system and engine. As gasoline degrades,it goes from clear in color to looking more like apple cider. This “apple cider”gasoline then begins to gum up your fuel system and your engine.
Can A Bad Gas Cap Make A Car Stall
Even worse, today’s gasoline often contains ethanol. When thesedeposits form, the ethanol in them attracts water from the atmosphere (it’s hydrophilicfor all you chemistry nerds).
Generally speaking, old gas in your car isn’t the end of theworld if you’ve let it sit for only a couple of months, but if your car hasbeen sitting for 6 months or more, you can run into some problems and you mayneed to use something like Seafoam.
We’ll get into what exactly you need to do in a bit.
Age is the most common cause of bad gas, but it’s far fromthe only one.
Water can also get into your gas tank. This can be caused by a loose gas cap, or from condensation. It’s also possible that water can make it in from the pump itself – although this is getting more and more uncommon.
Besides age and water, you may also have contaminated gasfrom a cracked fuel line, or from flakes coming from your gas tank.
What Are The Symptoms Of Bad Gas In Your Car?
Bad gas is fuel that doesn’t combust as expected. With thatin mind, most of the symptoms are related to the car not running as expected.
Your car relies upon fuel being delivered to the combustionchamber and igniting optimally. When this doesn’t happen, the car oftenhesitates and suffers from a lack of performance. With that in mind, somesymptoms of bad gas to look out for include:
1: Difficulty Starting Your Car
If your car cranks but won’t start, it could mean that youhave bad gas. Contaminated gas doesn’t provide enough power to start theengine. However – if your engine doesn’t start, you shouldn’t automaticallyassume you have bad gas. Anything from bad spark plugs to a busted fuel pumpcan cause your engine not to start.
If you have a lot of bad gas in your tank, this can causeyour car not to start in some cases.
2: Sputtering Or Pinging Sounds When The Car IsIdling/Driving
Bad gas doesn’t combust evenly – which can cause your engineto sputter or ping. Listen to your car both at idle and while driving atmoderate speeds. These noises aren’t the smoking gun on their own, because theycan also be caused by a bad fuel filter.
3: Stalling While Driving
If your gas is contaminated with sediment or with water, it’spossible that your car may stall while you’re driving because the fuel is notcombusting correctly. This only happens in extreme cases, so more likely thannot, it’s not something you’ll have to worry about.
4: The “Check Engine” Light Coming On While Driving
Can A Bad Gas Cap Cause My Car To Stall
Bad fuel can cause your car to run lean. If you have an OBD-II code reader, the code will almost always relate to your engine running lean.
5: Burning More Gas Than Usual
Can A Bad Gas Cap Cause Your Car To Stall
When you have bad gas, your engine will have to work harderthan normal to produce the same amount of power. This can show up as your car burningmore fuel than usual. On its own, this isn’t a smoking gun, but if you noticeit together with the other symptoms, pay attention.
6: Trouble Accelerating
If you have bad gas, it’s common for you to have troubleaccelerating or going up hills or other steep inclines because bad gas doesn’tburn correctly.
7: Speed Changes While Driving Without Pressing The Gas Pedal
Bad gas can also cause your car to abruptly change speedswhile driving. You may notice a sudden slow down, followed by a surge of speed.
What Are The Symptoms of Water In Your Gas Tank?
The symptoms of water in your gas tank depend on how much water gets into your gas tank. If there’s only a little bit of water, you might not notice it at all.
But if there’s a lot of water in the tank – you’ll definitelyknow.
The main thing to watch out for is hesitation when you tryto accelerate. When there’s water in your gas, your engine won’t be able toperform up to standard. The more water in your gas, the worse this will get.
The other symptoms I’ve already covered above.
So, Can Bad Gas Damage Your Car?
The answer is yes – but for it to get to that point you need to really let things go for a long time. Bad gas can form deposits that can cause issues in your engine. Again, this is very rare and probably won’t happen, but it’s good to know.
However, if you get bad gas from a gas station, you could be in for quite the repair bill. Although I’ve never seen the damage personally, I have seen reports ranging from $1,000 to $2,500+.
How To Get Reimbursed For Bad Gas
As I previously mentioned, most bad gas is probably not thekind you’ll be able to be reimbursed for. For example, if your gas goes badbecause it’s old you’re not going to get reimbursement.
However, if you put gas in your car and it almost immediatelystarts coughing and sputtering, then you may be on to something.
To prevent yourself from getting the shaft, you need to makesure you get a receipt. If you can prove you got bad gas from a gas station,then you’ll be able to get reimbursement.
More likely than not, you’ll be paid through the gas station’sinsurance policy. You may also want to call your state’s consumer protectionagency to report that you got bad gas to prevent others from getting burned asyou did.
With that being said – how can you be sure if you have badgasoline or not? You test for it.
How to Test For Bad Gasoline
The first thing you should do is ask yourself if it’s possible that your gasoline was contaminated due to your own error. Whether that was through letting your car sit, or through a loose gas cap, or something similar.
If you can rule these out, then it’s somewhat difficult to testthe gasoline without special tools.
A fuel test procedure and kit (without sending out to a lab)involves 3 steps.
- The first involves lowering a probe to the bottom of the tank with a paste that changes color if it touches moisture. The probe almost resembles a bicycle cable in a clear sheathe. This requires the probe and the color-changing paste.
- The second involves retrieving a sample of the gasoline. Place the gasoline in a graduated cylinder. Add some amount of windshield washer fluid. Cork the sample and shake the tube. Wait until it settles. Compare how much gasoline you put into how much is left after everything settles. This shows how much alcohol is in the fuel. It should be no more than 10%. All this test needs is a graduated cylinder that can survive gasoline. This is the easiest thing to acquire.
- The third involves retrieving a sample of the gasoline. This test measures the volatility of the gas known as Ried Vapor Pressure and requires another special testing tool. Chill the gasoline and tool on ice for 30 min. Pour the fuel into the tool and close it. Place the tool into hot water for 10 min and measure the water temperature. Read the pressure from the gauge on the tool. Compare the pressure and temperature to a table that comes with the tool.
How To Get Water Out Of Gas
If you have water in your gas, the first step is to figureout how much water you have in your tank. If your car is still drivable,chances are you don’t have too much water in your gas tank.
However, if you’re having serious performance issues – then you’llneed to go another route.
In this case, you have a few options.
They include using a product like Heet or by doing it yourself with dry isopropanol alcohol.
Considering Heet is about $3 on Amazon, it’s usually theeasiest option.
If Heet or isopropanol alcohol doesn’t fix the problem – thenyou’ll need to siphon the gas out of your tank.
Can A Bad Gas Cap Cause A Car To Stall
Get a fuel siphon, and then feed the tube into your gas tank and get pumping. Pump the siphoned fuel into a clear container so you can inspect it, and then refill your gas tank with good dry fuel.
Does A Bad Gas Cap Cause Stallings
How To Fix Bad Gas
Can A Bad Gas Cap Cause Stalling
Fixing bad gas, on the other hand, is much simpler. If you have true bad gas – not old gas, or waterlogged gas, then you’ll need to siphon the gas out of your tank and pump new gas in.
Don’t mess around with this, because bad gas can causedamage when it does happen, even if it only happens rarely.