I took the truck to AutoZone for diagnostics. Service Engine Soon light had come on day before. They did not show me the code, but said it registered a "Large Leak in the EVAP". I asked a few questions and they said a small leak is usually a gas cap, large leak is normally hose related.

I have done a ton of work on this truck and try to do everything myself. I have the Haynes Repair Manual.

Can anyone give me an idea where to start? What does this large leak probably mean?

Any help is appreciated. Thank you.

 

They may have it backwards.

Leaving the gas cap off, for example, will ALWAYS cause a P0455 on your generation truck.

Take it to a shop and have them smoke test it. It will be worth the diagnostic fee.

Steve

 

crawl under the truck and look for cracked hoses (under hood also)

Have you repaired anything lately? forget to put a hose back on?

cap --- definately large leak

check the fill hose, some b****** may have tried to steal gas!

Mark

 

I recently had my ford inspected and it said that I had evaporative emission control system problem. What is this and where would I look ??

 

did they give you a specific code?

 

If the gas cap has a minor leak in its seal with the fill tube, it will come up as a small leak. Thats why here in PA as part of emissions inspections they must test gas caps as well. My wife sport trac just trew the code, I looked at the tubing on the evap system and didnt see any problems. For what the cap costs, I would start there first. Then if that doesnt fix it, look at your rubber tubes next.