Back from Afghan!!!

[ArmyGuy45]

For those who do not know me that well, I am in the Army and stationed in Germany. I just got back from a 7 month deployment and told the wife to change the oil when I hit 4 months downrange. She never got a chance to do the oil change. So I changed the oil on the Jeep, it was pretty black and changed the rear diff fluid. The check engine light that came on while I was downrange was from two codes:

P0456: EVAP System very small leak

P0455: EVAP System large leak

The guy at the auto shop says the small leak can be from the gas cap not being on tight enough. We look at all the fuel lines for any leaks but didnt see anything but he thinks it could be the canister going bad. He cleared the codes and said we should wait and see if they come back. I wanted to get your guys input on what you think it could be. I do not notice anything wrong with the Jeep on performance or sluggishness.

[OrangeXJ]

Welcome back! Thanks for your service

[Mudderoy]

For those who do not know me that well, I am in the Army and stationed in Germany. I just got back from a 7 month deployment and told the wife to change the oil when I hit 4 months downrange. She never got a chance to do the oil change. So I changed the oil on the Jeep, it was pretty black and changed the rear diff fluid. The check engine light that came on while I was downrange was from two codes:

P0456: EVAP System very small leak

P0455: EVAP System large leak

The guy at the auto shop says the small leak can be from the gas cap not being on tight enough. We look at all the fuel lines for any leaks but didnt see anything but he thinks it could be the canister going bad. He cleared the codes and said we should wait and see if they come back. I wanted to get your guys input on what you think it could be. I do not notice anything wrong with the Jeep on performance or sluggishness.

Welcome back!

Hey is that the box thing near the gas tank?

[NW99XJ]

First let me say thank you for your service, and secondly, welcome back.
The auto shop guy gave you some good advice, unfortunately, these kind of leaks can be tricky to pinpoint.
I would think you should feel some sort of loss in performance with a "large leak"....unless it WAS something like just the gas cap.
The wait and see approach may be best at this point.... I know its not an ideal solution, but at this point, it's going to be hard to trouble shoot anything unless its more of a reoccurring issue.

[4.3LXJ]

Welcome back. The cure for the small leak is usually a new gas cap. I would start there, clear the code and see what happens.

[xj4life2]

Ok good info from all on the small leak however it could be that the Mrs. just didn't get the cap on tight enough when she fuel'd up, so first I would check to see its tight and then clear the code (disconnect the batt.) Then drive and see what comes back. If the large leak returns run a smoke test on the system (easiest way to find it). However I will say that on the newer XJ's its normally the Leak Detection Pump.If the small leak returns replace the cap of course. Good luck and welcome back !!!

[LizardRunner]

Welcome back, glad you make it out with no problems.

[denverd1]

welcome back and thank you

[cpttuna]

I paid $79.95 for a leak detection pump and that did not fix the problem. If you think it is the LDP, try some silicone or something around the connections to and from the pump first.

[bluedragon436]

Welcome home.. Glad to hear you made it out safely and back to your family.. I would say if the same codes come back, just to save a little bit of money, I'd pick up a new gas cap and get them reset and give that a whirl... just cause it is about the easiest and cheapest part to change for that stuff... and if it comes back start looking into other possibilities... I mean I guess it could be something with the canister up in the front bumper there.. that goes with the EVAP system...

[Dredwolf]

As someone else who spent time in A-Stan and most of it in Kunar and Nangarhar provinces, welcome home. Thank you for your service.

[XJ Wheeler]

Sounds like these guys got you covered, no more i could add anyway. Glad to have ya home, your service is greatly appreciated!

[ArmyGuy45]

Thank you all for the warm welcome. So far two days of driving and no codes. I will update this thread if anything comes back.

Thanks.

[ArmyGuy45]

Well Gents, the check engine light is on again. I have not ran it through the computer since 25 bucks per check so I am going to assume its the same codes. So lets start off with the cheapest way to fix/check this. New gas cap? Mine is a lockable gas cap and its about 3 years old.

[4.3LXJ]

The new gas cap is the first place to start and usually fixes it

[gary63]

lockable gas caps have a o-ring on the back of the lock cyl. that will dry out some times if you flush it out with wd40 the o-ring will seal up and it will seal. I have seen this happen on the locking gas caps. If not you are not anything exept a little wd40.If it dose work you can thing about a new cap or stay with the old one for now.

[ArmyGuy45]

The new gas cap is the first place to start and usually fixes it

Got any suggestions in case of the WD-40 trick doesnt work?


lockable gas caps have a o-ring on the back of the lock cyl. that will dry out some times if you flush it out with wd40 the o-ring will seal up and it will seal. I have seen this happen on the locking gas caps. If not you are not anything exept a little wd40.If it dose work you can thing about a new cap or stay with the old one for now.

[4.3LXJ]

Not really unless you can find the offending O ring and replace it

[gary63]

most of the screw on caps are crimped together some have 2 screws on the back undo
them and the back comes off.there is 1 or 2 small ball and the o-ring. if you get to it it is just a reg. ring that is ok around gas.

[ArmyGuy45]

Would liquid wrench in a spray can do the trick for sealing the o ring?

[apw5746]

Welcome back! Thanks for your service:patriot:

New to owning a Jeep, so I'm unable to help, but I'm sure there's enough experience on this forum to help you out.

Again, welcome back.

[gary63]

Would liquid wrench in a spray can do the trick for sealing the o ring?

yes all it going to do is swell the o-ring and sell up so it not leaking.

[ArmyGuy45]

yes all it going to do is swell the o-ring and sell up so it not leaking.

Awesome, thx. I will spray the o rings and then pull the negative cable to reset the computer. Will update in a few days.

[ArmyGuy45]

Light came on today. So who wants to send me a link of a lockable gas cap they trust.:D

[ArmyGuy45]

Ordered a locking gas cap from Napa, see how this one works out.

[XJ Wheeler]

I only trust Stant, tried others and had issues.

[ArmyGuy45]

New gas cap arrived today. Just reset the computer and now the wait begins.