Charcoal Canister Operation? (1 Viewer)

[NMC_EXP]

I have an '85 FJ60 with desmogged 2F. I believe my charcoal canister is causing problems. I will test it per the FSM. A search for charcoal canister pulls up several screens of good info. I'm trying to understand what inputs and outputs (vacuum and gasoline vapor?) flows in what direction thru the thing. Meaning what goes into the canister where and what comes out and where. I have not found this info.

Also there is and electrical gadget of some sort at the top of the canister

If anyone can give me a rundown of the plumbing on this thing and the function of the electrical gadget I'd greatly appreciate it.

I assume the "purge pipe" is manifold vacuum and the "tank pipe" is for gasoline vapor from the fuel tank but do not know for sure.

My canister looks like the diagram below: three pipes on top and one on the bottom. The two small ones on top are labeled "purge pipe" and "tank pipe". The large top pipe is not labeled. The bottom pipe is not labeled.

Thanks

Jim

 

[NeverGiveUpYota]

Bottom is vent, it goes into the frame rail to nothing. The one that routes from the driver side is evap/purge, the one from passenger is tank. Just follow them.

 

[NeverGiveUpYota]

Why do you think it’s not working? Do you get a big whoosh when you open the gas cap? If so you can gut and replace inner material, bunch of us have w/ good results or buy aftermarket. Wiring turns on and off the check valve I believe. Oftentje little section of hose shaped like an allow is severely degraded. I replaced mine w/ a similar elbow section of stock hose at Napa.

 

[NMC_EXP]

Thanks NGUY - good info.

Ever since I've owned it it usually had a little vacuum in the gas tank when I removed the cap.....it sucked. But ran fine.

Went to the Solid Axle Summit at Ouray CO. Combination of high elevation, long steep hills and warm temps and the 60 started running bad. Major power loss and hard misfiring on hard pulls. It was bad enough I did not run some of the high trails.

When I refueled on this trip the gas tank was usually but not always pressurized rather than vacuum. As in once it almost blew the gas cap out of my hand. That plus with engine warm but off I could burp the gas tank, put the cap back on, wait 30 seconds and the tank would repressurize with engine off....? That made me wonder if the charcoal was saturated with fuel and the engine bay heat plus altitude was boiling that off and causing a pressure build which was venting back into the gas tank....?

Many folks with carb equipped old Cruisers were having problems. General opinion was vapor lock and no doubt that was a factor. Then someone mentioned charcoal canister problems and suggested either running with the gas cap loose or stopping and pulling the gas cap and "burping" the tank once in a while. That seemed to help a lot.

The weird part was when it was puking its guts out with power loss on a hard pull I had black smoke coming out the tail pipe. That seems like flooding to me, not fuel starvation which I'd expect from vapor lock. The possible flooding plus a pressurized fuel tank made me wonder if the plumbing in the c-canister was malfunctioning so that pressurized fuel was causing the carb to flood.

That is why I want to understand the plumbing and valve arrangement in the charcoal canister.

 

[OSS]

At this point, all original charcoal canisters have obstructed or partially obstructed check valves on the "Tank" pipe nipple going into the canister. There's no way to clean them. The check valve is there to prevent air (and moisture) from migrating back into the gas tank. When the check valve obstructs flow, the gas tank can over pressurize and vapor lines can leak )or get blown off or seams in the tank can split.

The easiest cure is to just swap the purge & tank hose, but then that interferes with the EVAP system (which is an emissions system).

That big solenoid above the char can opens and closes the vent to the carb float bowl. It needs to be closed when the ignition is ON, otherwise starting can be difficult.

Also steep climbs and full tanks can sometimes purge liquid gasoline into the tank vent pipes, which gets sucked into the char can and then sucked into the base of the carb- flooding it. = black smoke.

 

[NMC_EXP]

OSS - good explanation & thanks.

This 2F is desmogged. I understand that reversing the purge & tank hoses basically deactivates the char-can. Other than releasing gas fumes to atmosphere is there any performance downside?

How can the carb vent solenoid be tested?

 

[NeverGiveUpYota]

vent to the carb float bowl

I feel like a wicked green newb now. Where and what is this on the carb.... flipping urgently through my emissions pages.

 

[OSS]

Technically, (though nobody including myself has verified if it makes a difference to mpg with testing) swapping the two hoses on the canister will cause the A/F mixture will be significantly richer than it was designed to be.

Normally, when the carb throttle plate drops below the advancer port (light cruising throttle or higher) the VCV that controls the purging of the canister opens and a significant vacuum leak is opened up at the base of the carb, sucking in air from the canister. This big "vacuum leak" during canister purging was accounted for by Toyota with the appropriate sized jets in the carb to hit a desired A/F mixture.

When the two hoses on the canister are swapped, the EVAP system no longer functions because the check valve in the canister blocks the flow- so the A/F mixture will be richer.

If this significantly impacts mpg or power or drivability or spark plug fouling or carboning up the combustion chambers .. is unknown.
Lots of people do the swap and the engine seems to keep running, so perhaps it's not significant.

The Outer Vent Control Valve above the canister is easy to check.

With the ignition key OFF, pull the big vent hose that connects to the big vent pipe on the side of that carb up top- that goes into the float bowl.

Blow air through it (with an extension hose so you don't get gas fumes in your mouth). Air should flow.

Then turn the ignition key to ON (but don't start engine) and do the blow test again. There should be no flow.

 

[NMC_EXP]

OSS

I've got to log out and do chores. If you have the time I'd like to discuss this more later on.

I may need to make myself a flow diagram of this system to understand it.

Thanks

Jim

 

[Willard]

Follow this
Aftermarket charcoal canister

and this

Charcoal canister hookup


Replaced my original Charcoal Canister with the AC Delco one and no issues. My bracket was toast, but I made it work and it does not move.
I would have preferred to go with Toyota, but really it is a canister filled with charcoal, as long as it is doing its job what does it matter.

My old one smelled like gas and nothing else. Once I resolved the bracket issue it took me less than 15 minutes.

Napa had universal T and straight fittings that worked just fine.

I will add I had the whoosh before and now it is gone. I have no idea if it fixed anything as I did mine while doing a ton of other work, I just remember the tank was pressurized when I parked it 2 years ago. I have replaced my tank since then, but it is currently 1/2 full and was driven a lot recently.

 

[OSS]

Toyota has a diagram

 

[NeverGiveUpYota]

I went looking at the carb I have in parts right now and I wondered if you were talking that port on the carb. I turned the horn over and can’t see any type of valve inside but I’ll take your word for it.
I’ve never thought swapping lines on the CC was a good idea. Lots suggest it but after seeing a comment Jim made once about doing it and something going ‘boom’ I decided routing should stay the way it’s intended.

 

[OSS]

Yeah the valve is on the cc. Not the carb

 

[slacker24-7]

I’ve swapped hoses on the canister a couple years ago on my desmogged 2F , it starts and runs great and gets 16 mpg with the city racer carb , no more tank pressure

 

[NeverGiveUpYota]

Yeah the valve is on the cc. Not the carb

Haha. Blame the blond roots again.

 

[roadstr6]

Another hose swap success story here. MPG didn’t change noticably and the truck runs fine.

 

[NMC_EXP]

Technically, (though nobody including myself has verified if it makes a difference to mpg with testing) swapping the two hoses on the canister will cause the A/F mixture will be significantly richer than it was designed to be.

Normally, when the carb throttle plate drops below the advancer port (light cruising throttle or higher) the VCV that controls the purging of the canister opens and a significant vacuum leak is opened up at the base of the carb, sucking in air from the canister. This big "vacuum leak" during canister purging was accounted for by Toyota with the appropriate sized jets in the carb to hit a desired A/F mixture.

When the two hoses on the canister are swapped, the EVAP system no longer functions because the check valve in the canister blocks the flow- so the A/F mixture will be richer.

OSS

Excellent explanation.

I do not know how to calculate flow rates thru a tube. But just looking at the cross sectional area of the main carb air inlet with approximate diameter of 3" and the canister purge to carb with approximate diameter of 3/8" the cross sectional areas are: dia. 3" = 7.1 sq-in and dia. .375" = 0.11 sq-in.

Total cross section area = 7.1 + 0.11 = 7.21 sq-in

% from canister purge line = 0.11 / 7.21 = 0.015 = 1.5% of total cross section area

I'm over my head with this but regarding performance, the air flow contribution from the canister purge does not seem significant.

If there was concern about changing the A/F ration when the two hoses were swapped disabling the canister purge to carb, I suppose a person could run the same size tubing from the clean side of the air cleaner to the purge intake port on the carb base.

Thanks again.

Jim

 

[Tennessee80]

I have a loud pressurized whoosh also…

I have a desmog 60 with city racer carb. Which one of these gets swapped?

 

[Roonie]

I swapped the 2 top hoses with the same clamps. I had the loud woosh when taking off the gas cap and now I don't. Also if I filled it up full and parked it the gas would overflow out the cap. This has been happening for years per evidence of my pic below and the permanent gas marks on the paint all because of the stupid charcoal canister.

 

[Tennessee80]

I swapped the 2 top hoses with the same clamps. I had the loud woosh when taking off the gas cap and now I don't. Also if I filled it up full and parked it the gas would overflow out the cap. This has been happening for years per evidence of my pic below and the permanent gas marks on the paint all because of the stupid charcoal canister.

View attachment 3438949

Thanks! My truck has been running rough and I’m trying to troubleshoot. Hopefully this illuminates the hooch sound, and I was hoping it would help my idle, but it didn’t.

Great looking rig, @Roonie !