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How to Troubleshoot a Malfunctioning Acura RSX Fuel Tank Cap

Failure of the Acura RSX's fuel tank cap is quite rare, but it can happen. And when the fuel tank cap does fail, it can compromise the fuel inside the RSX's fuel tank and, in turn, the performance of its engine. The following are some of the common problems associated with the Acura RSX fuel tank cap and how to troubleshoot them.

Check engine light is on

A Check Engine light on the RSX dashboard is one of the main indications of a malfunctioning fuel tank cap, but there are also other reasons for the light to turn on. If you have a handheld OBD scanner, you can use this to determine whether the check engine light is caused by a bad fuel tank cap. Hook up the scanner to the engine computer and check the code on the display. If the code is P0440 it means that fuel vapor is escaping from the tank, which is a likely indication of a malfunctioning fuel tank cap.

Dirty, corroded caps

If you notice sticky, old fuel residue on the thread and other parts of the fuel tank cap, it means that the cap is severely dirty and needs to be cleaned. Over time, particulates from the gasoline (particularly those that are of poor quality) may start to accumulate in and around the fuel tank cap. If left to build up, this can cause the cap to deteriorate and leak. The cap can be washed with lacquer thinner in order to dissolve the residue, but if it has already hardened to the point that it cannot be removed, it is recommended to have the gasket replaced with a new on instead.

Hardened gasket

If the gasket of the fuel tank cap has hardened and brittle to the touch, it may mean the gasket has worn out and needs replacing. Over time the gasket will dry out and become less pliable, leading to brittleness and eventual deterioration. Applying lubricating grease on the gasket will moisturize it and temporarily restore its pliability, although replacement of the gasket itself is a more permanent option.

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  • Simple Maintenance Guidelines for Acura RSX Fuel Tank Caps 27 February 2013

    Despite its diminutive size, the fuel tank cap of the Acura RSX is responsible for keeping the vehicle's fuel supply clean and safe inside the fuel tank. And while they will eventually wear out, regular inspection maintenance of the Acura RSX fuel tank cap can help prevent any serious problems and extend its service life.


    Inspect the cap for wear and damage.

    Aside from visible signs of wear, other tell-tale signs of a broken fuel tank cap include the smell of gas when the cap is screwed in and the lack of a hissing sound when it is unscrewed (both indicate that the tank is not pressurized and probably leaking air through the cap.


    Clean the fuel tank cap regularly.

    Over time, mineral particulates from gasoline will start to settle around the fuel tank cap. If left to accumulate, these particulates will form into a sticky orange buildup which might prevent the cap from closing properly, allowing gasoline to escape. To prevent this, regularly clean the fuel tank cap by washing it with lacquer thinner. However, if the buildup has already solidified, it may be better to replace the cap instead.


    Lubricate the fuel tank cap gasket with grease.

    The rubber gasket of the fuel tank cap will start to dry up and become brittle over time. To prevent this, apply non-reacting grease to the gasket on regular intervals. Keep in mind, however, that this will only minimize the hardening of the gasket, and once it becomes too brittle it must be replaced immediately.


    Make sure that the cap is always closed properly.

    The fuel tank has to be sealed at all times in order to ensure fuel efficiency and to prevent gasoline, which is a highly volatile liquid, to evaporate. Thus, it is important that the fuel tank cap is screwed in properly. If the tank cap is too loose, gasoline may leak out of it and become a potential fire hazard. But if it is too tight, the threads might become damaged. The stock cap of the RSX usually contains instructions on how it should be loosened and tightened. However, if you notice that the tank in your RSX isn't screwing in properly, check the threads as well as the various components of the cap for carbon buildup or damage.