CJ7 Evaporator canister

Mike Romain can get you set up back to the factory configuration.

The system is pretty straight forward..... it just holds gasoline vapors from the tank and ports them into the intake..

When mine crapped out I tried to drive without one, but the gas fumes were just too much. My wife insisted I replace it because her hair and clothes would pick up the fumes.

The canister is actually a needed part. It is the gas tank and carb float bowl vent.

Lots of folks have tried to do without a canister over the years, but none have posted back about any way to do it successfully....

Yes you can easily disconnect it by removing the tube from the carb float bowl and the gas tank tube and leave these open to the air. They cannot be plugged or the vehicle will starve for gas. Then the small line from the EGR/CTO system can be pulled off the top purge valve and be plugged.

This in effect vents your carb and gas tank to the open air. They will puke out an amazing amount of gas fumes on a hot day.

Some basics on it. There is a $2.00 filter on the bottom of the canister that should be changed with every major tune up or after a mud pit run. When it plugs up it puts a vacuum on the float bowl and gas tank which imitates running out of gas really well. I have had to drive home from the mud pits with my gas cap loose several times because I plugged the filter. I moved my canister way up by the brake reservoir to avoid this and put the washer tank down low. Changing the filter for the first time is a chore to dig it out. The new filter just tucks back in.

To test the canister for leaks, you start the engine and have it at idle then you pinch closed the line that runs from the PCV system at the rear of the carb down to the canister. If the idle changes, the canister purge valve is bad. If you think the plumbing to the purge valve (the little round thing on top of the canister) is bad/wrong, then just pull that little vacuum line off before doing the above pinch test.

If it fails the pinch test, then you need a new canister.

When folks remove the emissions computer and emissions crap for off road use, there are a couple basic players that still need to be in place for a good running engine. The PCV system, the air filter flaps that suck hot air on cold days so the carb doesn't turn into a block of ice and the gas tank vent or canister. Some engines run better with the EGR in place too.

The canister basic plumbing has a ported vacuum coming through the CTO valve and the air filter thermostat down to the EGR and canister purge. That is the small line to the top of the canister. This makes sure the canister doesn't turn on unless you are under throttle with a warmed up cooling system and a warmed up carburetor.

The large lines go to the carb float bowl and the gas tank. The purge line comes from below that little round disk up to a T fitting in the PCV line just behind the carb. If you have a solenoid thing there, you can toss it and just put a T fitting in. The solenoid never did work right and the factory fix was just a straight T so I have been told.

Here is a good site with most of the plumbing and other things explained:

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Thanks Mike. That was VERY helpful! I tried the pinch test last night and it still ran smoothly. (read: still misses every so often, but as I recall on my old carb'd car, that's the way it usually runs.)

Jeff asked how I knew it was leaking. That was really simple. There was a pool of gas dripping right under the canister and it smelled like gas. I then lit a match to confirm my suspicions, and blew the engine right out of the compartment. (Just kidding on the match.)

I've looked > When mine crapped out I tried to drive without one, but the gas fumes

Someone posted a while back about an aftermarket place selling canisters, but they are a real $tealership item. They are extremely expensive. Yours sounds ok so far...

Gas coming out of it means the anti roll over valve has failed at the gas tank or the plumbing is radically wrong and you have a full tank of gas. Maybe someone has the gas return line going to the gas tank vent and the return line spout at the gas tank going to the canister.

Or maybe the purge vacuum line has been disconnected for a long time and the charcoal has saturated? Hooking things back up right and going for a highway cruise would fix that.

I can turn my gas tank on it's side and it will 'not' leak gas out the two vent fittings that feed the canister. I know this for sure because I lost my gas tank on one off road run and had to plumb it into the back seat on it's side because the corner was ripped out of it. No leaks.

At the gas tank, you have one 5/16 nipple and line coming from the gauge sender pickup unit to the gas pump at the engine with a 3/8" nipple and line beside it that goes up to the engine to the gas filter's top outlet. The center outlet of the gas filter goes to the carb. It is important the return line is above the carb line or gas will syphon back to the tank when it sits and it will be a bugger on cold starts.

Then at the gas tank, you have two fittings that are rollover check valves with 3/8" lines that T together and come from there up to the canister.

'Maybe' someone got the two 3/8" lines mixed up at the tank?

As far as an idle rumble goes, that engine is a 'thumper' at idle if it is tuned for the emissions sniffer. It 'can' be tuned a bit richer if you kill the emissions computer which gets rid of the rumble, but then it won't pass emissions.

I have mine manually tuned with a hot ported timing curve and hot Accel spark so mine even rumbles and burps and goes on when decelerating down a hill just like the old muscle cars uses to do and still have to have that rumble to pass the sniffer. I have no emissions computer working in mine, it is all manually tuned. Goes like a scalded cat too...

Mike

jeepguymike wrote:

Mike,

Two things that I know of for sure: 1: my buddy that I bought the Jeep from replaced the entire fuel system, so what you said about the lines MAY hold true. I'll monkey with that tomorrow in the 90 degree heat we're getting here in Michigan.

And 2: Michigan doesn't have emissions testing, but they do in the detroit area, of which I DO NOT live (but grew up in).

All great advice! I did see the filters on a couple of web sites, so I may as well get those and replace them. I doubt anybody has, ever. I can afford to spend 2 bucks...

Updates tomorrow!

Is the emissions computer still in the ignition circuit?

A fast way to tell is to look at the plug on the ignition module that sits way down on the fender by the canister. The module has 3 wires coming out of it, an orange, a black and a purple. If it is still stock, the purple wire will terminate at the plug and not continue on. If the purple wire is connected, then likely someone has taken that poor excuse for a Ford emissions computer out of your misery.

And just FYI, I needed a hammer and chisel to get the first canister air filter out. It was a pain to dig all the pieces out, but after that the new filter tucks right in.

Mike

jeepguymike wrote:

Hi Mike, I've been having this same issue with fumes in my '84 CJ for a while. I just wanted to chime in and thank you for the time you spent explaining how to fix this.