Saddlehorn

Pulled the vapor canister out of my '73 and was wondering if anyone has used a '74 or later vapor canister in their pre-'74 vette? If so, any line hookup differences? Saw article on replacing the charcoal, but just plugging in a later year canister looks easier than trying to 'glue the old canister back together - and safer, I'd assume. Thanks for any input.

MajD

Check out this thread...I believe Tooch1 also has a 73. It looks like the bottom pops off with a screw driver, so you should be able to change the charcoal and filter and shouldn't have to glue anything back together.

https://www.corvetteforum.com/forums...-question.html

Good luck.

MajD

Alan 71

Hi S,
I think the determining factor may be the number of 'pipes' on the top of the canister you choose as a replacement.
For instance 70-72 canister tops have the line from the separator on the side of the tank, and then two lines running to the carburetor.
I think your 73 has 3 pipe/lines also?
I believe some later canisters have just 2 pipes?
Regards,
Alan

When you pop off the bottom it gives you access to the fibrous 'pancake' filter, but not the charcoal itself.

MajD

Never mind...I see it looks like the second filter screen has to be cut out to get to the charcoal. Sorry about that.

MajD

Saddlehorn

Thanks - appreciate the response. It does look like I'll have to cut the old one open to replace the carbon. Have heard of folks using JB weld epoxy and/or super glue to glue the canister back together. If the canister is polyethelene, then not many glues will work well.

Alan 71

Hi S,
Member CraigH from Australia posted a thread in which he gives instructions and photos showing how to replace the charcoal in the canister.
Regards,
Alan

https://www.corvetteforum.com/forums...-canister.html

Click Craig's link in post #3.

DUB

Odd question,

Why do you feel you need to replace the charcoal??

DUB

Saddlehorn

Noticing a gas smell in garage, but not bad. The canister is original but the car was stored for many years before I got it. Possible the carbon is still OK? I checked to see if the gas odor was coming from the vicinity of the gas tank, and it is not. Gas tank is new and the 'vent' device on the tank top (side) was replaced at the same time.

Alan 71

Hi S,
I believe I'd check that the fuel separator on the side of the gas tank is actually in working order, and that the hose connections at the top of the canister and at the carburetor are correctly run.
If the 2 hoses running from the canister to the carburetor aren't routed properly, and to the correct ports on the carburetor, the vapor which has attached to the surface of the charcoal charcoal won't be drawn into the engine to be burned.
If there is an excess of vapor (more than the charcoal can store) the vapor is vented through the bottom of the canister. That's why some folks begin by replacing the pancake filter which is easy/inexpensive to do.
These can all be done before resorting to replacing the canister or the charcoal in the canister.
Regards,
Alan

Tooch1

Having just gone through all this with my 73 ( see my previous posts), recheck everything, especially the hoses going to the canister. You state yours is original, make sure the hoses aren't dry rotted or cracked. My original hose 'yellow stripe" connecting the canister to the metal line going back to tank was cracked. But I couldn't see that until I crawled under the car. It looked ok up top. But it was bad at the clamp connection. My previous posts on here show how to change the lower filter. Another place to check for leaks, even though you say you have a new tank, is around the filler neck. Pull up your rubber boot back there and check the gasket area where the filler neck is attached to the tank. My car had a new tank installed too by the previous owner, but two of those little screws connecting the neck to the tank had the rubber seal washers missing and I was getting some seapage around there. Just saying!
Hope this helps,
Jimmy

Saddlehorn

Alan - good input. Found the line from the carb port on the canister was hooked up to the window washer of all places!! Where on the carb does this go - to a port on the carb to manifold base or to a port toward the upper portion of the carb. I have later (electric choke) model Qjet on the car. Finding numerous vacuum hose routing issues with the canister hoses. The PCV hose is connected directly to the intake manifold fitting, so more work to do here. May ask for more help on proper routing as my AIM is really fuzzy on these hoses. Thanks again for getting me on the right path.

Saddlehorn

Thanks - I'll be checking those areas today. Really appreciate the input as the Corvette has been a real learning experience for me.

Saddlehorn

Another question - what type of line did you use to replace the 'yellow stripe' line to the gas tank? Just fuel hose from the auto parts store? Thanks.

Tooch1

Here are a couple pics showing where my 73 hoses coming from the EVAP canister go. The larger one coming off it comes up to the pcv valve as marked on the top of the canister. Then it goes to the lower right side port on the carb. Attached with a clamp. The skinnier ribbed white stripe hose follows the same path, and connects to the lower port on the left side of the carb as shown. I used a replacement hose for now to connect the canister to the metal fuel vent line going back to the tank. It must be for fuel. They are made different (stronger) than a vacuum hose. However, all the vendors sell the hose and clamps. But it doesn't have the stripe. Original clamps for the larger hose are yellow, and red for the smaller hose coming off the canister.
Regards,
Jimmy

Tooch1

EVAP hoses to carb.

Tooch1

Another view. This shows where the large hose goes. Hope these help!
Tooch

Alan 71

Hi S,
The small diameter hose (white stripe in 71) runs directly from the canister nipple to the carburetor while the large hose runs from the canister to a 'T' at the PCV valve and then on to the carburetor.
Regards,
Alan

Here's an overall view to go with tooch's detail views.

Saddlehorn

Thanks Jimmy - this really helps. My canister was obviously not connected correctly. I think every hose needs to be rerun.

Tooch1

No problem,
Let me know if you need anything, if I can help I'll be glad to. I can't imagine having that hose hooked to the wipers
Tooch

DUB

Thank you for answering my question on why you want to mess with the charcoal canister.

From experience working on these old Corvettes.

DO NOT assume that your metal vapor return line that runs parallel with your brake line on the frame is in good condition. I have lost count with how many EVAP systems I have repaired where the steel line was rusted out and actually had a split in it. Or it was plugged up and the vapor line was useless.

I would get the hose off BOTH ends of this line and see if you can blow air through it. IF you can...so far so good. The the next test is to plug one end of the line and using hand vacuum pump...pull a vacuum on the line and make sure it holds vacuum. Because if it does NOT hold vacuum...you have a problem somewhere in the line that needs to be replaced. Or you will still have fuel vapor smell in the garage.

DUB