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Unread 11-12-2013, 01:57 AM   #1
zjilla
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evap system leak?????

I got this code read: what should i be looking for? There is no physical damage to the canister...whats my next step in detecting where its leaking

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Unread 11-12-2013, 03:10 AM   #2
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i just ordered a new fuel cap off amazon. we will see where that takes me
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Unread 11-12-2013, 06:59 AM   #3
ridesno4llfe
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Check the hoses coming off the canister as well. They can rub through anywhere they come in contact with the body or frame. Had a similar issue with my wifes Liberty. PO had installed a sub and drilled a hole in the firewall for the main battery feed. Right through the evap line running on the otherside. Took me forever to find.
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Unread 11-12-2013, 08:13 AM   #4
mello
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I hope the cap resolves the concern but don't get your hopes up. Most of the time a cap is only the concern when left off after fill up and then it will cause a gross leak code. A small leak in a EVAP system is sometimes impossible to find without a smoke machine. It is not always a hose or line, could be a vent solenoid , a pressure sensor, a wiring concern, or several other things.
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Unread 11-12-2013, 12:30 PM   #5
awinski
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smoke test, if i remember correctly p0456 is a small leak, aka .020-.040"
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Unread 11-12-2013, 01:31 PM   #6
mello
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It is a small leak and a smoke machine is the best way to find a small leak. The higher end scan tools will run an EVAP test but it will only help to find a large leak. The smoke machine is fool proof and eliminates quests work.
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Unread 11-12-2013, 05:22 PM   #7
73azbronco
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What's up with the chinsy sounding clunks you get when you shake the evap canister? Is that normal? Sounds like a box of rocks being shaken if you shake it.
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Unread 11-12-2013, 05:29 PM   #8
mello
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Quote:
Originally Posted by 73azbronco
What's up with the chinsy sounding clunks you get when you shake the evap canister? Is that normal? Sounds like a box of rocks being shaken if you shake it.
The charcoal filter could be busted loose inside or at least that is what it sounds like.
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Unread 11-12-2013, 05:36 PM   #9
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Can yall go into detail how to preform the smoke test? Are there other threads on it?

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Unread 11-12-2013, 05:52 PM   #10
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You need a smoke test machine and either pull a relay or jump the solenoid to keep it closed. The machine attached to the fuel system and pumps smoke into it and then you hunt for the smoke coming out of somewhere just like you look for air bubbles on a leaking tire with soap and water.

It could also be the evap pump. How the computer works is the evap pumps up the fuel tank/system until it can not pump anymore, the computer reads how much current is drawn by the pump if the pump keeps pumping like there is a leak or it is not pumping sufficiently the computer reads the current draw and turns the light on and sets the code.

It could be a gas cap, line leaking, tank leaking, seal somewhere leaking, wiring issue, pump issue, canister issue, computer issue. Most common causes I've seen are the pumps bad or a leak somewhere.
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Unread 11-12-2013, 05:55 PM   #11
mello
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You have to have a smoke machine and they are pricey. Dealerships and high end shops have them for diagnostic purposes. Their sole purpose is EVAP diagnosis but they work great for vacuum leaks, exhaust leaks, and finding boost leaks in turbo and supercharged applications. All tool trucks sell them but would not be a good investment for just a one time use. Would be best to take to someone who has one and knows how to use it.
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Unread 11-12-2013, 06:18 PM   #12
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there are smaller machines that pump pure smoke. your vent solenoid is normally open allowing evaporating gasoline from the tank into the evap canister. once there is enough pressure the purge solenoid (normally closed) opens to allow those fumes into the engines intake. no idea if the jk has a service port or what not, but the point is to close the vent solenoid to seal the system, then check both ends for leaks.
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Unread 11-12-2013, 06:34 PM   #13
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As said about ten times now, smoke test is the best way to go, we do it at the shop all the time. Or just ignore it until emissions time
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Unread 11-12-2013, 10:31 PM   #14
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Early JK's use a primitive evap system. Basically a purge valve and a spring loaded valve in the attached white box to the canister to vent and release vacuum.

An ESIM (evap system integrity monitor ie- crap) is used as a switch to determine If system pressure or vacuum is present. The white box on the back of the canister contains the valve.

Unlike a modern closed loop feedback system which monitors fuel tank pressure FTP with a FTP sensor and adds a computer controlled vent solenoid Chrysler saved a few bucks and went with the pop off valve a a set of look up tables for purge strategy.

I know that's TMI but we find bad or aftermarket gas caps the number one cause and the ESIM number two. The valve can stick and there is a rubber o-ring between the canister and ESIM that can fail. The ESIM is cheap and easily replaced.

We have had a few where holes were drilled in the floorboard to mount things and the canister was punctured or a hose torn. Dealers mostly guess and replace the canister and ESIM.

Smoke is the best way to find the leak, be sure to pinch off the vent line when testing. Virtually all modern vehicles have a EVAP test port, look for the green cap on the line near the purge valve
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Unread 11-12-2013, 11:23 PM   #15
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I had the P0456 code last week.
Looked things over, then cleared the code.
It hasn't come back since.
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