About a month ago my gas cap light came on (didnt even know i had one). so i pull over, take it off, inspect it and put it back on. I pull into an oil can henry's for them to read the code and turn off the light. It was just an emissions thing that is usually a lose gas cap. a week later it comes back on so i went an got a new cap and had the light turned off. about a week later it comes back on and this time with the CEL also. The CEL code was 455 evap emission control/system leak. had both those turned off. now my gas cap light is back on. Any ideas where to start looking for a leak or something that is causing this? and how would i be able to find the leak (assuming its small since the light stays off for about a week)

 

I have a obo11 scaner and can turn off the light but I believe you need to undo the batt for awhile to clear the code from the computer. Turning the code off isnt the same as clearing it. Try that.

 

The fuel tank must reach a certian pressure otherwise the code / light will always come back on.

In my experiences with fords and this code, there is some sort of evap purge valve that tends to goes bad. Check into that first. (of coarse you'll check all the vacuum lines *first*)

Rich

 

P0455 and the Check Cap light are both for a major leak, not a small one. That should make it easier to find.

Recheck the security of the clamps at the filler neck hoses. Since you have a body lift, that's a definite possibility.

 

ok, thanks guys. Ill check those

 

I just checked all the obvious places and there was no leak as far as i could tell. Will ignoring this light cause any problems aside from just being annoying? Seems pretty harmless.

 

I don't like driving anything with a fuel system leak whether it be vapor or liquid.

Also, in Fords, the monitor uses engine vacuum to test the integrity of the fuel tank and peripherals. So, if you have a fuel system leak, it is sucking unfiltered air into the engine, maybe a little, maybe a lot. IMO, any unfiltered air is too much.