2003 explorer sport trac fuel problem

My check engine light came on. Then after a few days the check fuel cap light came on. The code said air leak.
I changed the fuel cap no joy.
I checked all lines going from fuel tank no joy.
Any ideas?

By all lines do you mean vacume/vapour return lines? Could be a bad vapour management valve (I beleive that's what they are called) they regulate the vapours going back to your gas tank neck and are part of the emission control. You can send smog into the system to check for leaks if your mechanic shop is equiped for it.

Welcome to the forum!

What is the exact code number that you found? There are quite a few emissions-related codes for air leaks, so knowing the exact code will help hone in on the real issue or problem area.

If you don't have the full code, swing by a local chain auto parts store. Most will read the codes at no cost, but be sure to get the actual code (in the form of P1234) rather than the salesperson's interpretation of the code.

-Rod

The codes are
0455 evap large leak
0457 gas cap off

I all ready replaced the gas cap with no change.

The code P0455 is EVAP Control System Leak Detected (No Purge Flow or Large Leak). According to the factory service manual, this can be casued by:


After-market EVAP hardware (such as fuel filler cap) non-conforming to required specifications
Disconnected or cracked fuel EVAP canister tube, EVAP canister purge outlet tube or EVAP return tube
EVAP canister purge valve stuck closed
Damaged EVAP canister
Damaged or missing fuel filler cap
Insufficient fuel filler cap installation
Loose fuel vapor hose/tube connections to EVAP system components
Blockages or restrictions in fuel vapor hoses/tubes (items also listed under disconnections or cracks)
Fuel vapor control valve tube assembly or fuel vapor vent valve assembly blocked
Canister vent (CV) solenoid stuck open
Mechanically inoperative fuel tank pressure (FTP) sensorThe code P0457 EVAP Control System Leak Detected (Fuel filler cap loose/off). According to the service manual, this can be casued by:

Fuel filler cap not installed on refueling (storing continous memory DTC) and "Check Fuel Cap" light may also be illuminated
Fuel filler cap missing, loose, or cross-threaded.-Rod