How to diagnose "Check Gas Cap" warning?
#1
07-17-2018, 04:11 PM
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How to diagnose "Check Gas Cap" warning?
This is for my 2012 F250.
My list of what I'm going to try/have tried:
Done:
1. Get out and unscrew, then screw back on
2. Unscrew, fill to top with gas, screw back on
Haven't Done Yet:
1. Unplug battery cables to reset the sensor? (worked for Thread 1 OP) [actually just pull the PCM KAM fuse so I don't have to reset other electronics like radio, resetting computer will get rid of light but problem may remain]
2. Buy a new cap
3. Check fuel line from cap to tank and evap canister? (check vent hose from gas tank to canister)
4. Take rubber seal off and flip it over (may be a nick in seal) [could also add a little vaseline to gasket to get better seal) (clean any dirt or rust off till end of tank opening)
5. Remove gas cap, then start truck and let it run for a few minutes. Then turn off and turn back on. (Thread 2, Pokermunkee, Durango 2007)
6. Replace purge valve in fuel system, costs $200 (Thread 2, Mattster344, 2011 F250) ((also worked for Bigjeffs350, ths thread)
7.
Possible Causes
1. Hit a pot hole
2. Something leaking between tank and gas cap opening or canister?
3. Purge valve went bad
Previous Threads on this topic:
1. Fuel Cap Warning Light (For a 2008 5.4L Gas)
[url]https://www.ford-trucks.com/forums/1162946-fuel-cap-warning-light.html
2. 2011 F250 6.2 "Check Gas Cap" ?
https://www.ford-trucks.com/forums/1...k-gas-cap.html
Last edited by slogward; 07-17-2018 at 04:13 PM. Reason: links
#2
07-17-2018, 04:29 PM
Postmaster
#3
07-17-2018, 04:40 PM
#5
07-18-2018, 06:37 AM
#6
07-18-2018, 07:56 AM
Hotshot
There are a number of things that can cause that message. It's important to actually go through the troubleshooting process to figure out what is wrong instead of just guessing.
Inspecting the gas cap and its sealing surfaces is the first step since those are the items that get a lot of physical wear and tear during normal operation.
Inspecting the gas cap and its sealing surfaces is the first step since those are the items that get a lot of physical wear and tear during normal operation.
#7
07-19-2018, 11:37 AM
For what it’s worth, I flipped the o-ring on my gas cap and nothing changed. Put a new gas cap on yesterday, started the engine, and still got the error message. Drove for about an hour today with the new gas cap on and noticed that the gas cap error message had disappeared, so evidently the systrm needs to run a bit to reset.
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#8
07-19-2018, 01:33 PM
Hotshot
During driving, he OBDII check for the gas cap requires that 1) A fill-up (or significant increase in fuel level) has to be detected and 2) The initial portion of an evaporative leak diagnostic be performed. The error cannot clear without both prerequisites and certainly won't be cleared just by starting the engine back up. The truck has to be driven.
#9
07-19-2018, 02:33 PM
During driving, he OBDII check for the gas cap requires that 1) A fill-up (or significant increase in fuel level) has to be detected and 2) The initial portion of an evaporative leak diagnostic be performed. The error cannot clear without both prerequisites and certainly won't be cleared just by starting the engine back up. The truck has to be driven.
i didn’t put any gas in; tank was/is 3/4 full. Maybe the sloshing around the tank while driving around made the system think there was more fuel in there. Who knows....message is gone at least.
#10
07-19-2018, 04:14 PM
Hotshot
#12
07-20-2018, 10:53 AM
While you’re waiting for your new gas cap, keep the old one on with the seal flipped over to see if maybe that fixes it after driving awhile.
#14
07-20-2018, 05:15 PM
Hotshot
Canister purge valve.
I’ve replaced them in two different Subaru’s, a Hyundai, Honda Element and 3 other cars (people I know).
The only time I have seen a gas cap fail...
#15
07-20-2018, 05:22 PM
Fuel pump gasket will cause this too. Clear all codes with your OBD tester and it's doubtful you will see this again in the next 3-6 months. I had this pop-up after changing the pump after about 6 months, and since it's a PITA to get to the tank, I found later that I had just not seated the pump well enough.