Skip the auto shop - Our mechanics make house calls

Symptoms of a Bad or Failing Fuel Filler Cap

fuel filler cap

Bad or Failing Fuel Filler Cap Inspection

by a top-rated mechanic at your home or office

The gas cap is a very simple, but important component that is found on the vast majority of road going vehicles. It’s purpose is to ensure that no dirt, debris, or dust enter your fuel tank, and that none of the fuel vapors escape. The gas cap plays an important role in the proper operation of the vehicle’s evaporative emissions system, which is designed to trap and reuse fuel vapors that would otherwise be released into the atmosphere. As the gas cap is removed every time the vehicle is refueled, it will often wear out simply due to repeated use. While a faulty gas cap will not necessarily cause major performance issues, it can cause the vehicle to experience fuel and emission problems. Usually a bad or failing gas cap will produce a few symptoms that can alert the driver of a potential problem.

HAVE SYMPTOMS OF CAR TROUBLE?
Get an $80 diagnostic
by a top-rated mechanic at your home or office.

Get a quote · Book an Appointment · Our expert mechanics come to you.

1. Cap does not tighten properly

One of the first symptoms of a bad or failing gas cap is a cap that does not tighten properly. Most fuel caps have a built in mechanism that will cause them to click once they are adequately tightened. If when tightening the cap, it does not eventually click, or pops loose after it clicks then that is a sign that the cap may be damaged and need to be replaced.

2. Fuel smell from the vehicle

Another symptom of an issue with the fuel cap is a fuel smell from the vehicle. If the gas cap leaks, or fails to provide a proper seal it can cause fuel vapors to escape from the fuel tank, which may cause the vehicle to give off a fuel smell. A fuel smell can also be caused by various other issues, so a proper diagnosis is recommended if you are unsure.

HAVE SYMPTOMS OF CAR TROUBLE?
Get your car fixed at your home or office.

Get a quote · Book an Appointment · Our expert mechanics come to you.

3. Check Engine Light comes on

Another common symptom of an issue with the fuel cap is an illuminated Check Engine Light. If the fuel cap has any issues sealing the fuel tank it can cause the Check Engine Light to come on for evaporative emissions system reasons. The vehicle’s evaporative emissions system is designed to trap and reuse fuel vapors, and can detect if there is a leak in the system. A leaky fuel cap will compromise the effectiveness of the evaporative emissions system, and as a result will set off the Check Engine Light to notify the driver of the issue. A Check Engine Light can also be set off by a wide variety of other issue so having the computer scanned for trouble codes is highly recommended.

While a faulty fuel cap probably won’t cause any major drivability issues with the vehicle, it can cause the Check Engine Light to illuminate. If you suspect that your gas cap may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the cap should be replaced.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Still not sure about your car's issue?
Diagnose your car
What kind of issue are you experiencing?
Brakes are squeaking
Car is not starting
Car is overheating
Car is shaking (vibrating)
Fluids are leaking
Heating and A/C
Smoke or steam is coming out of the car
Warning light is on
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...


Related questions

Q: RPMs erratic during idling, Check Engine Light on, P0174 code

Hello. The P0174 code deals with the truck running lean. That means that the PCM is restricting fuel to the injectors. This is usually caused by a vacuum leak in the engine. There could be a leaking intake gasket, or...

Q: Replaced fuel pump. Car won't start. 2002 Infinity I35

Hi there - the metal component you describe is a fuel check valve on the fuel return line. Its function is to maintain a small amount of pressure in the fuel system so that starting does not require the fuel...

Q: Fuel cap indicator not working

Hi. I assume your Check Engine Light is on and you have an evaporative emissions (EVAP) code stored. Your cap may not be sealing well, even if it is on and tight. I would start by replacing the cap first...