Charcoal canister purge valve question
 

How might I check the purge valve on my 72 C10 charcoal canister to verify if it's good or bad? Another question is why is it needed if one of the lines is connected to the pcv line? Seems like it would constantly be purging the gas fumes. I also think I read the purge valve should be connected to ported vacuum? Right now the only thing connected to the canister is the 3/8 fuel line. I don't smell gas fumes, but would like to hook it up correctly. Thanks.

Re: Charcoal canister purge valve question
 

Re: Charcoal canister purge valve question
 

The basic idea as I understand it is:

• When vacuum is not applied to the purge valve, the connection to the PCV valve outlet is closed. So you should be able to leave the purge valve disconnected and verify you can't suck on the PCV hose outlet on the charcoal canister and get any air, or not much air. Then when you open the valve by applying vacuum to the purge valve, you will be able to draw air from the PCV hose outlet on the charcoal canister.
• If you connect it to ported vacuum, your charcoal canister is out of the circuit at idle. This keeps your charcoal canister setup from giving a vacuum leak at idle, so keeps your idle smooth. Drawing fumes from the charcoal canister and burning them is what happens when your driving down the road or other non-idle conditions.

If your purge valve is not working and the PCV port is wide open all the time, you can just plug the purge valve port and get an external purge valve and hook it up inline with the PCV port.

Re: Charcoal canister purge valve question
 

Thanks DJ. I'll check it out tomorrow if I can find my mighty vac. Instead of teeing into the pvc hose what are your thoughts about connecting to another manifold vacuum port on the carb? Smaller fitting than pvc, but since I'm not smelling fumes now it might be ok.

Re: Charcoal canister purge valve question
 

I have a 69 with no vacuum canister and I rarely smell fumes even parking in the garage. The vapor system probably gives just a very marginal advantage, barely anything. It would probably be OK to suck the fumes out of the canister through some other vacuum port, it just wouldn't be set up according to design. If you have 50 year old activated charcoal in the canister, it may not be doing anything for you anyway.

Re: Charcoal canister purge valve question
 

I have to disagree with: "very marginal advantage, barely anything." Or at least when my '72 Charcoal canister wasn't working. The vapor smell was pretty bad in the garage and into the house if I left the door opened.

After getting mine replaced/fixed (it was damaged) and then a recharged one installed was like day and night - meaning I went from having fuel smell to zero. So for me it was well worth the effort of getting it figured out.

Here is another link, which this helped me recharge a Canister. Unless you are very lucky to get a NOS one, you will need to recharge it.
Vapor Canister Rebuild - A new how to

Interestingly I have a 1969 AH Sprite in the garage now and it doesn't have a canister. The Sprite isn't causing a fuel smell. Makes me wonder if you have a car that is designed with one and it isn't working/disconnected you'll get vapor smells vs a car that never had one.

Re: Charcoal canister purge valve question
 

Yes, I meant comparing to a 69 just plain vented cap gas tank, a properly working whole vapor system probably gives just a very marginal advantage, barely anything. It is more stuff to maintain, and if something goes wrong with it there will be a stink. if I were inclined to add the vapor system to my truck or repair a vapor system, I would get a new canister, which is fairly cheap and does not have the built-in purge valve. I would then just get an external purge valve and hook it up.

Re: Charcoal canister purge valve question
 

This canister on Amazon has purge, tank, and air ports. (thinking the air port would be pvc) Looks like I could remove the cap on the air port and add an external purge? I've emailed Dorman. Anyone tried something like this?

Re: Charcoal canister purge valve question
 

Nice write up, bookmarked. I smelled gas in my garage recently, may have to rebuild the can at some point. Its early take off, but

Re: Charcoal canister purge valve question
 

Sure would be great if thats a replacement option

Re: Charcoal canister purge valve question
 

DJ I can suck air through the pvc fitting when there is no vacuum on the purge and line disconnected. I pull 15 inches of vacuum on the purge and it holds. Pvc still open.
Would this purge valve be the one for the pvc line? I assume the purge valve is connected to the pvc outlet inside the canister?

Re: Charcoal canister purge valve question
 

I can only give opinion based on my limited knowledge, I have a 69 and only have studied this vapor stuff when I have considered adding some vapor control, but lost enthusiasm for it when I saw how much extra money it was going to cost, at least a few hundred $$ for gas tank, sending unit, vent lines, gas cap, hoses and hard lines, canister, purge valve. Others here on the forum may have more experience with this. But here goes because I like to type, I'm too tired to go back out to the truck and crawl up under that dash for my current project.
I think that purge valve would be the one to get to operate external of the charcoal canister. It would connect to the PCV outlet on the outside of the canister.
I believe the canister listed on Amazon is what you would need, and connect the PCV outlet on that to the purge valve, and on the other side of the purge valve tee that into the PCV line. The tank port goes to the gas tank vent, and the air port just sits there are vents or sucks air and it is not designed to fit a hose.

Re: Charcoal canister purge valve question
 

^ Must be a different design than I'm used to. IIRC, the ones for our vehicles had a filter on the bottom of the canister that needed periodic replacement. Connections were to fuel tank, purge line and vacuum.

Re: Charcoal canister purge valve question
 

Yes, that type is no longer made.

Re: Charcoal canister purge valve question
 

If you're working on it I recommend ordering the purge valve first and check it to see if it behaves like I described, because you never know I may have it all wrong. During my research I didn't find any really good detailed descriptions of how the system worked and had to make some assumptions.

Re: Charcoal canister purge valve question
 

DJ there isn't a pcv port on the canister. Just the capped off air, fuel tank, and purge. It almost looks like the air is capped and might come off. If it did wonder if I could use that for the pcv connection. Probably just pulling fresh air through the canister and that's probably what the pcv fitting does. Your thoughts?

Re: Charcoal canister purge valve question
 

The purge port is the PCV port. The air port is probably equivalent of the original canister, having that air filter on the bottom to vent the canister, and should be left as it sits. That is my guess.

Re: Charcoal canister purge valve question
 

Here's how the '70 CA model (LS9) was plumbed:

both the skinny lines in the circles go to the canister.
IIUC:
The port on the right sits higher in the carb, so that's the bowl vent.
The fat PCV port sits under the blades, so that'd be manifold vacuum and would draw fumes from both the canister "return" hose and the driver's valve cover into the carb.

Mine is also the type with the 12k mile filter replacement. Filters are available from Rockauto, but the canister itself is not.

Hope this helps

Re: Charcoal canister purge valve question
 

Ordered the ACDelco purge valve. Film at 11.

Re: Charcoal canister purge valve question
 

The Delco purge valve will work. Smaller than the pictures and they don't say the line sizes. The diaphragm vacuum nipple is 3/16 and the through line is 5/16. With no vacuum the 5/16 through line is closed and opens at approx 5 inches of vacuum applied to the 3/16 line. I'm gonna make it work with the available 2 port canisters. Just tie the 5/16 into the pcv line and the 3/16 to ported vacuum on the carb. I hope. Thoughts??

Re: Charcoal canister purge valve question
 

It sounds reasonable to me.

Re: Charcoal canister purge valve question
 

Why couldn't I skip the purge valve and connect from the port on the canister to ported vacuum on the carb? It just wouldn't involve using the pcv tee. Thoughts anyone?

Re: Charcoal canister purge valve question
 

I don't know why they designed it the way they did. It could be ported vacuum only works well to control valves and actuators that do not leak. I don't know if it is a concern that air going into the small ported vacuum port is clean and limited to a very small volume, while air going into the large manifold vacuum port used for PCV is OK to have gas and oil vapors in it and leak in at a steady stream.

Re: Charcoal canister purge valve question
 

Checked with the manufacturer of the canister to make sure the purge port isn't a purge valve. It isn't so DJ using the external purge valve is the way to go.
Checked the canister purge port on the quadrajet today and it is ported vacuum. Excellent!
Thanks

Re: Charcoal canister purge valve question
 

Not sure why they'd use ported vs manifold for evap, but for PCV, I'd think you want that port below the blades to keep the oil vapor from condensing and gumming things up.

Re: Charcoal canister purge valve question
 

I can't picture how to connect an external purge valve to a canister. Image of the assembly would be great.

Re: Charcoal canister purge valve question
 

Rust, the main line will be teed to the pcv and the ported line is just to signal the purge valve to open and dump into the pcv line.

Re: Charcoal canister purge valve question
 

The line from the PCV to the carb. has a tee anyway, to reduce it from 3/8" to 1/4", which connects to PCV on the canister.

By the looks of the 214-2294 Vapor Canister Purge Valve, would it be correct to install it near the replacement canister? It looks like you just cut the PCV hose near the canister, install the valve to the PCV hose, install the vacuum hose and done.

In other terms, this seems to demonstrate how the original cans work, and how to modify the evap. system using the newer cans. At least to my understanding. Any corrections appreciated.

Re: Charcoal canister purge valve question
 

Tony, the top fitting is marked purge and the bottom is tank vent. No vent marked pcv on the one I ordered. (not here yet) Hooking up the main line on the valve to this purge fitting. I measure 5/16 on the purge valve line so I ordered a 3/8 x 5/16 red tee for the pcv tie in. My carb has a canister purge vent which is ported vacuum and will open the purge valve when off idle. I think this Frankenstein deal will work. Where did you find the diagram? I had to draw one in my head.

Re: Charcoal canister purge valve question
 

PCV on the old canister is Purge on the newer ones.

5/16" for the PURGE port or the valve? Hmm... The existing PCV hose is 3/8", and reduced to 1/4", which ran to PCV on the old can (PURGE on the new can). The only 5/16" hose in the original EES system is for TANK. Where do you plan to install the purge valve? Bummer of it has to be installed by the 3/8" hose; i wouldn't think it hangs above the manifold. Hoping it installs with the 1/4" hose, near the can.

I drew up the illustration, so this replacement can business can sink into my head:lol:...Already had the info. for the original can.

I revised the illustration (1973-74) because I think the cans changed in 1973. Also, the 911-261 can's stated dimensions are larger than original, perhaps it won't fit in the original bracket and strap. That's assuming the stated product dimensions are right, which they probably aren't, I'll bet that's the package dimensions.....Can #215-153 shows closer dimensions to common 71-72 truck canisters, which are approx. 5.75" tall and 5" wide, or 6.75" tall if counting the valves.

Re: Charcoal canister purge valve question
 

Tony I measure 5/16 on the valve through line. Maybe I'll have the can today. Film at 11.

Re: Charcoal canister purge valve question
 

Well, 1/4" is almost close 5/16":lol: Make sure your new hose is for fuel (PCV/EEC), IMO. Some install plain fuel hose, but the PVC/EEC hose is specifically for the task.

Edit.... For what worth I asked for the dimensions on a 17113148 canister. It's 5" wide like our old cans. It's 6" tall without the valves, which about 1/4" taller than our cans. Perhaps a light provision necessary, I don't know why this can for example wouldn't work like original by adding a purge valve.

Perhaps available cans (1973-ish) are the same size for standard fuel tank capacities, which our cab tanks are approx. 21 Ga.

Re: Charcoal canister purge valve question
 

Question. Will I need to remove the battery tray to remove the canister??? Looks real tight in there.

Re: Charcoal canister purge valve question
 

I didn't need to pull my battery tray. There was just enough room to get it out with its brace (as one), though for a bit I thought I was going to need to pull it. I did have the 12v power junction off the fender so those power lines were out of the way.

Re: Charcoal canister purge valve question
 

Thanks Rich. I was hoping to hear that. Should be interesting. I don't need to remove the bracket unless I need to. Just the canister.

Re: Charcoal canister purge valve question
 

Rich, I held my tongue just right and the whole thing came out. The best part is the aftermarket canister fit the bracket. I was a little worried about the fit.
Thanks

Re: Charcoal canister purge valve question
 

That’s great to hear, would love to see photos with it all connected up and well it works!

Re: Charcoal canister purge valve question
 

HEY! You didn't tell me how hard it was to reinstall the bracket. Sheet metal moved just enough so the front screw couldn't start. I got it. By the way the canister is a touch larger diameter than the original. Not enough to be a problem. Snugged right up. I pulled the filter from the bottom of the old canister. I advise anyone to do this over a garbage can. Everything was dissolved inside except the charcoal. Still loose after 50+ years and smelled like gas. There's a lot of charcoal in there and it goes everywhere. Don't ask how I know this.
Thanks

Re: Charcoal canister purge valve question
 

I can't remember if I pulled my can and bracket as a unit, but I recall it can be done either way. I pull the battery just cuz. If I read you right, the fender ("sheet metal") moved a touch. Perhaps a good reason to pull the can w/o the bracket.

I have a new system short the can is used. It's original and in prime shape cosmetically, and I tested the diaphragm before I installed it. But after 300 miles, my garage stinks when I repark the truck, for about an hour or so. My suspicion is the charcoal has seen enough emissions.

They leak due the foam rubber at the bottom is toast.

So anyway, I'm probably due a new can and IMO, better to buy new if it works than refresh an original can, at least for convenience.

Did you get everything hooked up? We're waiting for a full report:lol::chevy:

Re: Charcoal canister purge valve question
 

My diaphragm tested ok on the old canister. It held a vacuum. DJLambert said the diaphragm would open the pcv port when activated. That would purge the canister. My pcv port was open at all times. By the way my canister was not hooked up, but just the tank vent attached. Got tire of smelling gas in the garage. Been that way for a long time.