1999 Cherokee sport 4x4... got a weird one here... So my light is on and i read the code and its a small evap leak. I filled my gas tank up and it disappeared after about a quarter gone. Then half tank came back on. Any clues?

Or just get it smoked?

 

While never a good idea to shoot the parts cannon at the Jeep when I had the small evap leak CEL I threw a new gas cap on.
Figured it was cheap enough. Been good ever since.

 

I had the same issue for about a week...every day. There is a run of vapor lines on the drivers side frame rail that do a lot of interconnecting between plastic to plastic and plastic to metal connected by rubber couplings that get sloppy with age. These couplings start at the front side of the door and work their way into the engine compartment below the brake booster. If you give a gentle tug on these lines the worn ones pull right out 5/16 fuel line was a good replacement. I have been code free for several weeks now. NOTE..the small plastic lines are brittle try not to bend too much

 

I had the same problem a a few years ago what I did was took off all the hoses cleaned the part that slides over the other part and then used a spring clamp to help hold it tight .

 

I did try a gas cap, still there. I'm thinking as said above its a small rubber hose somewhere. I might just have to get it smoked to see. It's been a pain.

 

I wish I knew where everyone of them was id just replace them all haha. She's been a pain in the rear lately.

 

Yep, just went through this again this summer. Follow the line from the purge pump (passenger side under hood near firewall) to the drivers side engine bay and then down to the drivers side frame rail. It will continue to the gas tank. More then likely you will find your leak. Get ready to make a trip to the parts store for some different size hose ( gas, evap) and replace where necessary. You might even find that your hard metal line is rusted through. Just replace it with some brass barb fittings and (gas, evap) hose.

 

Smoke test is your friend for evap leaks. I know most people don't have smoke machines laying around in their garage, but not too hard to rig up something that gets the job done. I have made my own with a mason jar and a couple of hoses and small harbor freight 12v pump when I needed to smoke test my F150 a while back. Worked well enough I found the leak and saved me a diagnostic fee at a shop.

 

How did you make "smoke"

 

A wick, mineral oil and a thin heating element (wire) from a toaster.

 

I fought that code for some time as Chrysler used tubing that's not rated for gas fumes, (always replace with fuel line) and the plastic retainers grow brittle with time. - wire ties are an Jesper's best friend.

 

Sooo if I don't let it fall past 3/4 full in the tank the light stays off, no check engine light in over 3 weeks

 

I saw a Youtube of a dude exhaling cigar smoke

depending upon which US State you are in, and your own inclination, I can think of something else if you dont like tobacco lol

I have performed a vacuum test using lungpower a few times

 

These couplings start at the front side of the door and work their way into the engine compartment below the brake booster.
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Mine was the rubber rotted and the metal line was rusted out between the gas tank and the evap canistor.