EVAP System issues

[Spectre]

Sorry this post got away from me and became pretty long..

02 KJ. 2wd with the 6 cyl motor

I'm not familar with the jeeps yet.. (This is my moms car) Anyhow..

She keeps getting p0455 and p0442 codes.. Evap leak and Evap Gross leak detected..

Replaced the gas cap.. No good. Finally crawed under it.

Next to the gas tank is a sqaure box with hoses going to it.. (I'm guessing it's the charcoal canasiter) Well the rubber line that went to the middle was split and hanging off of it. I went to reaplce it but the dealer wants $54 for a little rubber hose that's only 4-5 inches long.. (banghead) I bought a generic rubber hose to reaplce it but of course the side on the canister is larger so it wouldn't fit. I ended up taping it up real good with electrical tape and put it back on for now to see if it would fix the issue

Well the CEL came back on and the same 2 codes came back. So either my shotty ghetto fix didn't work or there's another leak somewhere else..

Is there known issues with specific parts of the EVAP systems that are known to fail?

Under the hood there's a green cap on the lines.. Which I believe is a service port to test the system.. Is there a home mechanic way of testing it that someone can enlighten me on? Or am I going to have to pay the stupid $80 for a shop to do a "smoke" test.

Stupid thing needs to be smogged in 2 weeks.

 

[IceColeNH]

I am having a similar issue. You need to check the lines all the way through.
Start at the front where the purge valve is and trace lines all the way back.
Quite a bit of rubber. You'll need 5/16, 3/8, 1/2 hoses. Most people are using fuel line hoses.
The Ones near the fire wall are exposed to alot of heat thus crack easily.
Then down the line near the transmission are two more rubber hoses.
Now back near the rear arms/ differential. Trace all these lines looking for cracks. You may just want to replace all of them anyway because of age.

Don't forget near the fuel filler. Use a light to look up there. Or you can remove the wheel well liner.

I also dropped the tank and replaced some hoses there. Be careful. Less fuel in tank the better.

Hope this helps...

When looking if you could see if you have a small check valve (black and green) up near the filler. I would greatly appreciate it..

 

[ShafferNY]

Just thinking out loud. What are the chances of using some dry ice for a backyard mechanic smoke test?

 

[ShafferNY]

http://www.dsmtalk.com/forums/showthread.php?t=216701

 

[Spectre]

I thought about a fog machine to do it, but not sure on how well it'll work.. hmm.. I may have to try it..


I'm also thinking of just hooking up my compressor to it and have a helper pressurize the line while I go underneath with a spray bottle with soapy water to look for bubbles.. Same way to look for a hole in a tire..

 

[ShafferNY]

I'm also thinking of just hooking up my compressor to it and have a helper pressurize the line while I go underneath with a spray bottle with soapy water to look for bubbles.. Same way to look for a hole in a tire..

If possible, set your air compressor regulator to a really low pressure and connect the air hose to a line. Then do the soap test as mentioned.

As long as the pressure is really low, you should be able to find the leak pretty easily. If you set the pressure too high, you'll probably create leaks, blow hoses off, etc.

In the link I posted above they caution about pressurizing the system. They say there is a chance of an explosion. I'm not sure I believe that. You're more likely to simply blow a hose off before you reach enough pressure to cause combustion.

I mean, you can compress an air fuel mixture of 14.7:1 up to probably ~120psi(or higher) in a gasoline engine and not have to combust. Hence the need for a spark plug.

 

[tjkj2002]

If possible, set your air compressor regulator to a really low pressure and connect the air hose to a line. Then do the soap test as mentioned.

As long as the pressure is really low, you should be able to find the leak pretty easily. If you set the pressure too high, you'll probably create leaks, blow hoses off, etc.

In the link I posted above they caution about pressurizing the system. They say there is a chance of an explosion. I'm not sure I believe that. You're more likely to simply blow a hose off before you reach enough pressure to cause combustion.

I mean, you can compress an air fuel mixture of 14.7:1 up to probably ~120psi(or higher) in a gasoline engine and not have to combust. Hence the need for a spark plug.

Never pressurize the EVAP system past 2-3psi,you will cause leaks by doing that.

For intake leaks a $5 can of throttle body cleaner works wonders.

 

[Spectre]

Never pressurize the EVAP system past 2-3psi,you will cause leaks by doing that.

Good thing I read this before I did anything..

For intake leaks a $5 can of throttle body cleaner works wonders.

I know to find intake leaks to use the Throttle body cleaner trick..

I'm going to be buying a replacement hose for the one I tried to fix to see if that's going to fix the problem..

Though thinking out loud here.. When the vehicle is running there should be some kind of preasure in the EVAP system.. So couldn't the soapy water trick work? I don't think it would be able to suck enough water through to hurt the motor.. *shrug*

 

[jnaut]

Do tell, what is the trick with throttle body cleaner to find intake leaks?

 

[ShafferNY]

I know to find intake leaks to use the Throttle body cleaner trick..

I'm going to be buying a replacement hose for the one I tried to fix to see if that's going to fix the problem..

Though thinking out loud here.. When the vehicle is running there should be some kind of preasure in the EVAP system.. So couldn't the soapy water trick work? I don't think it would be able to suck enough water through to hurt the motor.. *shrug*

I don't think the soap test will work that way. The lines are under vacuum when the vehicle is running.

If I'm not mistaken, the system does go through a breif self text when the vehicle is first started, where by it pressuresized the EVAP system to check for leaks. If the system doesn't hold pressure, it throws a code. Depending on how big the leak is, dictates which codes it will throw.

As for the throttle body trick, if you spray the outside of the throttle body with cleaner and the engine rpms pick up, you've found your leak. Pretty old school, but it works. We used to use the same trick with starting fluid on carbureted engines. You can also check for intake leaks this way.

 

[Spectre]

I don't think the soap test will work that way. The lines are under vacuum when the vehicle is running.

It wouldn't show bubbles like if there was pressure, but wouldn't the suction distort the soapy water?

*shrug*

 

[ridenby]

Do tell, what is the trick with throttle body cleaner to find intake leaks?

Spray around gasket areas,if engine gains speed,that is the leak.

 

[bigben0003]

did you ever find a hose that could fit?