Symptoms of a Bad or Failing Fuel Filler Cap

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.

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.

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.


Next Step

Schedule Fuel System Inspection

The most popular service booked by readers of this article is Fuel System Inspection. Once the problem has been diagnosed, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Fuel System Inspection reviews

Excellent Rating

(6)

Rating Summary
5
0
0
1
0
5
0
0
1
0

Joseph

27 years of experience
578 reviews
Joseph
27 years of experience
Ford Ranger V6-3.0L - Oil/Fluid Leak - Richmond, Texas
Great service
Ford Mustang - Pinion Seal Replacement (Rear) - Houston, Texas
He was there earlier which was great. Got the job done quickly with no problem.

Rigoberto

11 years of experience
739 reviews
Rigoberto
11 years of experience
Buick LeSabre V6-3.8L - Oil Change - Rolling Meadows, Illinois
Very thorough, polite. I would always use him on my car repair.
Honda Accord - Car Starter Repair - Chicago, Illinois
Amazing experience. Very knowledgeable and obviously knows his craft. Very good at explaining what was going on. I was nervous about using yourmechanic but so happy I did. Saved a lot.

Johnny

33 years of experience
264 reviews
Johnny
33 years of experience
Toyota Corolla L4-1.6L - Fuel System Inspection - Sacramento, California
Johnny did a great job

Raymond

37 years of experience
402 reviews
Raymond
37 years of experience
Chevrolet Impala V6-3.4L - Fuel System - Las Vegas, Nevada
Raymond was very knowledgeable mechanic and through in his testing. I trust him for any future from your mechanic.

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

Related articles

Symptoms of a Bad or Failing Fuel Return Hose
If your car has a carburetor and it gets flooded, fuel is leaking, or the car smells of gas, you may need to replace the fuel return hose.
How Long Does a Fuel Pump Last?
With With all of the different components that allow your car’s fuel system to function, it can become very hard to keep up with them all. Having malfunctioning components in your fuel system can lead to a variety of issues...
How Long Does a Fuel Return Hose Last?
Most Most of the older cars on the market have a carburetor that helps to disperse the fuel that is need during the combustion process. While these carburetors are very reliable, there are a number of repair issues that can...

Related questions

Fuel Injector Replacement, BMW 1988 BMW 325i
Yes, on this model BMW you can replace one injector individually relatively inexpensively. If you are able to afford it and are fairly certain it is an injector problem, I would suggest replacing them all at the same time while...
Installed new battery won't start - 2001 Dodge Durango
There are number of things that may cause an engine not to start which may or may not be related to the battery. This may be related to many different possibilities, some of which may be related to a lack...
Fuel tether turns with gas cap, causing the gas door (flap) to close.
Hello there, a few common faults will cause your 2004 Hyundai Sonata to have issues removing the gas cap. In cold weather the gas cap seal can become stuck, this will allow the gas cap to turn but not fully...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com