You will usually receive an indicator light when your car’ computer has found a leak in the system. In many cases either the fuel cap or check engine light comes on when there’s a problem with your car’s gas cap. Many times the gas cap is just loose, and the problem can be solved by removing and putting the cap back on tight … until you hear the clicking sound. You may also smell gasoline, due to fumes escaping around the loose gas cap. Once it’s on correctly, it’s safe to continue driving the car and the light should reset itself and turn off after several engine restart cycles.
If you discover that the cap will not go back on tight, then you have a broken or defective cap and it should replace it. The average gas cap can last for over 50,000 miles, and even longer. But it’s a good idea to check it regularly for fit and cracks or broken pieces.
A bad gas cap won’t cause engine shut down or electrical/power issues. A broken, or even no gas cap, will cause gasoline to evaporate from the system and decrease fuel pressure to the engine, causing engine misfires eventually. Over time, engine misfires can create other costly issues, and shouldn’t be neglected.