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Unread 01-18-2016, 03:21 PM   #1
Js139
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EVAP Leak - Not the standard question

So like many people here, my Jeep has developed an Evap system leak. I've been slowly (in my spare time) working my way through the diagnosis list that was in some present threads. I replaced the fuel cap with a new OEM one and that wasn't the issue. I inspected the hoses near the battery and they showed some signs of wear. I did a quicky fix to test that and that isn't the issue.

However, as I have been working on this, I've noticed a weird trend with my engine error. It is definitely intermittent and the light goes away when I get to the bottom 1/4 of my fuel tank. When I fuel up, it is fine for a day or so and then the light comes back. When I get to about 3/4 tank, I get the "Gas Cap" error in addition to the check engine light. That stays until a half tank or so and then the check engine light stays on until about a quarter.

It is super weird to me that the fuel level impacts this, but it has done the same thing for 3 tanks now. Anyone else notice this? I'm thinking it has to be the pump in the back and I am just going to replace that. I'd rather replace the whole system and be done with the annoying light, but part of me wants to know why it reacts the way it does and what is causing this issue. Is there some sort of check valve on these that might be sticking as well? Thoughts?

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Unread 01-18-2016, 03:29 PM   #2
2Rad4U
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Jk? If so, mine was #2

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Unread 01-18-2016, 07:05 PM   #3
Js139
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Originally Posted by 2Rad4U View Post
Jk? If so, mine was #2

Yes, it was on my 2011. Are you saying you had the same symptoms as mine?
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Unread 01-20-2016, 04:11 PM   #4
Maertz
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Quote:
Originally Posted by Js139 View Post

Yes, it was on my 2011. Are you saying you had the same symptoms as mine?
The tank fill level triggering it is due to the fact thats when the evap is cycling.... Evap codes are not constantly monitored in a way.
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Unread 01-20-2016, 06:15 PM   #5
ronjenx
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Quote:
Originally Posted by Js139 View Post



It is super weird to me that the fuel level impacts this...
The ESIM, (Evaporative System Integrity Monitor), conducts tests on the evaporative system as follows: An engine off, non-intrusive test for small leaks and an engine running, intrusive test for medium/large leaks.



Conditions for running the intrusive EVAP test are:

After the vehicle is started, the engine coolant temperature must be within 50F of ambient to indicate a cold start.
The fuel level must be between 12% and 88%.
The engine must be in closed loop.
Manifold vacuum must be greater than a minimum specified value.
Ambient temperature must be between 39F and 98F and the elevation level must be below 8500 feet.
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