How to Rebuild a Vapor Canister

jiho

G-Body Guru
Jul 26, 2013
856
63
The third port on this so called new replacement can likely controls some sort of built in valve with an unknown function which could cause EVAP operation issues. Basically the compatibility is doubtful.
Pull out the vacuum pump and test it. The factory shop manuals show the various types, find out which it is and go from there.

The 2-port canister has 1 port for the vent line to/from the tank, and 1 port for the vent/purge from/to the bowl/intake. GM had a field day making variations on the theme, but ultimately they all had to serve the same basic functions: vent the tank, vent the bowl, purge the canister. Rearrange the hoses and you should be able to convert one variation into another.

I'll refrain from suggesting where the 3rd hose might go. :mrgreen:
 
Last edited:

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
5,597
113
Olds has the most discombobulated setup I've ever seen. It used a TVS and a Canister Control Valve that was vacuum operated to determine when to vent and when to purge based on running or what coolant temperature was. While it was super simplified at the canister, the top of the intake just couldn't be simple. Along with the fact of cramming everything into one corner of the intake manifold. Solenoid operation would have worked better, but the OBD1 system likely wasn't thought of as a possibility at that point since they started using this type of junk prior to OBD1. The ECM already had temperature inputs and controlled the EGR solenoid already, so what's one more little solenoid?

Refresher course- easy peasy:

There's only one reason to keep all the junk in that canister system, and that's if you're staying stock, or current regulations in your area mandate they be there. The more complicated canisters with the control valves on top of them may be easier from the engine side of things, I don't know.

from my 87 442 (other Oldses are similar). TVS would be just off the picture in the extreme most bottom LH corner. Welcome to Spaghetti Town.
VIN9canisterventvalve.jpg


The key player- Canister control valve:

CCVoperation1.jpg


Operation per CSM (note- V8 does not use the thermal bowl vent):
CCVoperation2.jpg

CCVoperation3.jpg
 
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MJScarangella

Greasemonkey
Sep 24, 2020
240
63
Pennsville, NJ
There's only one reason to keep all the junk in that canister system, and that's if you're staying stock, or current regulations in your area mandate they be there. The more complicated canisters with the control valves on top of them may be easier from the engine side of things, I don't know.


I still have the gas tank plumbed to the canister in the engine bay; I haven't swapped the fuel sender/pump in there yet. I was considering leaving the canister in place. I've read a bit about evap and I'm not quite sure of how the evap system valves work. It seems intuitive that it isn't good to pull a vacuum on the gas tank, because it will implode. So, does a functioning evap system pull a vacuum on the canister while some valve to the gas tank is closed? What is the basic premise? Obviously not a simple premise due to all the hoses.

People have told me to vent the gas tank to the atmosphere. Someone told me to use a roll-over valve like they use on off-road jeeps. I bought one; it has a flame screen on it to keep fire from propagating down the vapor line.

Can I rig something that functions better than venting to the atmosphere or venting to the orphaned canister?

Anyway, if nobody suggests a better solution, I will vent the gas tank to a roll-over valve in the engine bay, and dispose of the charcoal canister (sell it if someone wants it). I don't plan to roll the car, but the rollover valve has a nice barb on it and it'll be easy and fireproof. I don't like gas smell; makes people like my wife the car is a hack job.

My harness and ecm have evap delete.
 
Last edited:

Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
2,664
113
Galaxy far far away
I still have the gas tank plumbed to the canister in the engine bay; I haven't swapped the fuel sender/pump in there yet. I was considering leaving the canister in place. I've read a bit about evap and I'm not quite sure of how the evap system valves work. It seems intuitive that it isn't good to pull a vacuum on the gas tank, because it will implode. So, does a functioning evap system pull a vacuum on the canister while some valve to the gas tank is closed? What is the basic premise? Obviously not a simple premise due to all the hoses.

People have told me to vent the gas tank to the atmosphere. Someone told me to use a roll-over valve like they use on off-road jeeps. I bought one; it has a flame screen on it to keep fire from propagating down the vapor line.

Can I rig something that functions better than venting to the atmosphere or venting to the orphaned canister?

Anyway, if nobody suggests a better solution, I will vent the gas tank to a roll-over valve in the engine bay, and dispose of the charcoal canister (sell it if someone wants it). I don't plan to roll the car, but the rollover valve has a nice barb on it and it'll be easy and fireproof. I don't like gas smell; makes people like my wife the car is a hack job.

My harness and ecm have evap delete.

My suggestion is just leave the EVAP intact. Open venting is super crude and emits a ton of pollution, hence the gassy smell. Plus open ventings lets moisture in the tank which degrades the fuel system faster.
 

sldwys

Greasemonkey
Thread starter
Nov 21, 2020
128
28
.....and that right there is why I hate car shows and restorations! So, extra port or a glue seam that's not factory? I feel like I'm on classicoldsmobile all of a sudden.
The ports on the new one were smaller nipple than my stock hose(didn’t want to put reducer or any makeshift piece to hook it up)So decided to scrap it and use the guts on my original.
 

sldwys

Greasemonkey
Thread starter
Nov 21, 2020
128
28
Also this isn’t a show car. Just a man in his quest with lots of headaches to keep it stock.
 
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