'86 AE 82 clogged charcoal canister from tank

[rickhart]

Tested the charcoal canister as per shop manual and it was clogged from the tank line but not the carb line. Replacement of the canister is not an option and the junk yard ones were clogged too.

So I disconnected the hose and fashioned a one-way valve on the tank hose (venting it to the outside air) to keep air and gas vapors from going back and forth. Result is that car isn't so easy to flood when starting after being driven for a while, stopped, and then restarted while still very warm. Note that this doesn't happen in the dead of winter when it's too cold for the gas to have any vapor pressure. Starts quick and idles smooth without any initial roughness.

I suspect that the vapor pressure in the tank pushes gas into the carb flooding it and causing a gas smell that's most noticeable in a closed garage. Venting some vapors to the outside air actually causes less air pollution than all that liquid gas evaporating in the intake manifold, not to mention washing away the motor oil off of the cylinders (aka "dry start").

Has anyone around here done this too ?

[iringtwice]

I had taken my 87 Corolla to 2 different mechanics one who is suppose to be a Toyota expert, and both were not able to solve this hot weather starting problem I was having. After reading your post I pulled the "to engine hose" off and ran it awhile with the ac on. Stopped at the store to get beer came back and it CRANKED RIGHT UP! Thanks for the tip, are those canisters hard to find? Mines probably shot from this test. Until I can find a replacement I will just leave the hose off. THANKS!

[rickhart]

I've lost track of how many posts described this flooding problem and seems like nobody ever considered the canister as the source of the problem. It was always seen as a carb problem and things usually got worse and expensive from there-----rebuilding the carb, replacing the carb entirely or at least the float. I don't think you can find new or usable canister anywhere. The manual says that it's not rebuildable even if you can figure out how to remove the top part.

You do need to install a one-way valve on the vapor hose from the tank to keep air and humidity from being pulled into the tank when it cools. I used one of those from the disconnected EGR system, bored out the IN and OUT hole some to increase ability to vent more vapor, and used a short piece of small ID hose as a bridge. The OD of the bridge hose matched the ID of the tank hose. The pressure needed to open the one-way valve seems to be alot less than the pressure buildup that pushes gas through the needle valve on the carb float.

[rickhart]

Also, ran a foot-long piece of the small ID hose from the outlet of the one-way valve into one of those pre-drilled holes in the strut column to vent the gas fumes out of the engine compartment. Fire hazard otherwise. Jammed the end of the hose behind some kind of metal lip inside the column so it wouldn't get caught up in the strut spring or vent against the rubber boot.

[Gokhan]

Actually it turns out that it's very easy to repair the charcoal canister. The problem with it is fuel-varnish deposits on the spring of the No. 1 check valve. You can easily dissolve the varnish deposits using Gumout carburetor & choke cleaner, a hose attached to the tank port, and a compressed-air gun (up to 100 psi compressed air). There is no need to bypass the charcoal canister and vent the tank vapors into the atmosphere through an external check valve, which results in increased pollution and decreased fuel economy.

I've posted the detailed instructions on how to correctly do this at a new thread here.

Rick, thank you for getting me into doing this repair. It was the last thing on my engine that had to be done. It now runs as good as new.

Also note that part of the problems with hot starting on 4A-LC engine is inherent and due to improper choke action. Since the choke is vacuum-controlled, it takes a while for the vacuum to form and the choke opener to function. The bimetal in the automatic-choke housing also cools down and closes the choke, adding to the problem. The owner's manual instructs to fully depress the accelerator when cranking a hot engine but this is detrimental to the engine as it would rev like crazy -- so do not do this. I've figured out that the best way to start a hot 4A-LC engine is to depress the accelerator only very slightly before and during cranking and keep it very slightly depressed until the engine starts running smoothly.