Charcoal Vapor Canister Replacement with ACDelco Canister

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El Dorado Hills, CA
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For the last little while, whenever I would open up the gas tank I would get a little bit of pressure release - whoosh. I have a metal LRA tank and so as the problem got worse, I would hear the sheet metal occasionally "pop" as the pressure developed - whomp whomp. At the time I didn't know where the whomp whomp was coming from - fingers crossed this fixes it. Last week I went to fill up the tank and got such a face full of air that I knew I had to figure out what was going on. I sent a message to @orangefj45 and he let me know that it was likely my charcoal canister.

I purchased the ACDelco vapor canister that a lot of others have mentioned. ACDelco - Vapor Canister (SLP-1) (215-153) , Black Amazon product ASIN B000C9I9GQ
For those getting ready to do this project I wanted to point out a few things that would have saved me a couple of trips to the auto parts store.

  1. There are three hoses on the OEM canister. Two on top and one on the bottom. All of the hoses are 5/16 fuel lines. The one on the bottom is a fresh air vent which needs to be rerouted to the big 1/2 port on the top of the new AC Delco canister
  2. The AC Delco uses three different hose sizes which makes it a little tough to get everything to connect up right.
  3. The AC Delco has a larger diameter. The metal bands that hold the OEM canister will fit around the new AC Delco one but you'll have to make some adjustments

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IMG_7770.jpg
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These first few pictures show the parts I used to connect the fresh air port underneath to the 1/2" line that now has to run up to the top of the ACDelco canister. The canister comes with a little clip on cover that needs to be removed to attach the 1/2" line.


Because the diameter of the ACDelco canister is larger, the ends will no longer make it all the way around and bolt together. I ran over to lowes and got a 2.5" bolt with a nylon lock nut. You will need to get two of each. Tighten it down, but don't go crazy because the new canister is plastic. While outside of the vehicle, I put the bottom mounting strap around the canister and climbed under the vehicle, I bolted in one of the strap flanges to the mounting bracket and then got out from under the vehicle. I then put in my 2.5" bolt and nut on loosely so that it could still be adjusted on the canister until I could get it bolted to the upper mounting bracket. Once it was tight on the upper mounting bracket, I then made myself into a contortionist and got two ratchets going to tighten down the 2.5" bolt.


In IMG_7770 above, you can see that the left side is bolted to the mounting brackets and the right side is about a mile away. Again, because of the larger diameter there isn't a way to mount this in all 4 mounting locations. The canister is super light weight, and because we used bolts instead of zip ties to tighten the bands around the canister, I'm not concerned amount only having it mounted in two spots instead of four.

Now that the canister is mounted in the vehicle it's time to get all of the hoses adjusted to size and mounted up. You will need 1/4", 5/16", and 1/2" hoses.

I couldn't find the right brass fittings to adjust the tank vent line so I had to use a doorman universal thing. Pictured here.

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IMG_7772.jpg

This last picture was tough to get any detail, but you can see that two of the mounting bracket wings are out in mid air. The other side is bolted up tight on both though.

Hope that helps the other greenhorns like me.
 
Interested in a second report on the whooshing next time you fill the gas tank.
 
does the fresh air vent really need to be rerouted?
 
When the gas tank is filled to the brim, (which should never be done) the EVAP system can (and will) suck liquid gasoline into the charcoal canister and actually set up a siphon for a while. Under the right circumstances, (over filled tank) liquid gasoline can be seen gushing out the bottom of the original charcoal canister when it happens.

When the canister becomes completely saturated with liquid gas, the evap system starts sucking in liquid gas directly into the base of the intake manifold whenever the throttle passes the advancer port (just very light throttle but not idle).
Engine won’t run when it’s sucking in gas like that and will stumble whenever the gas pedal is pressed.

Luckily with the original OEM charcoal canister, it can clear this problem naturally, given enough time, as the fuel will eventually drain out of the bottom of the charcoal canister and it will be cleared out.

But with this AC Delco canister- I can’t see any drain in the bottom of it. If that’s so, it would FILL TO THE BRIM with liquid gasoline during an overfill event and have no way to drain out.

Bottom Line:
NEVER EVER fill the gas tank to the top.
 
does the fresh air vent really need to be rerouted?
I’m not sure but the reason I did it was in case the canister ever completely fills with gas I’m hoping that the gas gets routed out of the engine compartment.
 
When the gas tank is filled to the brim, (which should never be done) the EVAP system can (and will) suck liquid gasoline into the charcoal canister and actually set up a siphon for a while. Under the right circumstances, (over filled tank) liquid gasoline can be seen gushing out the bottom of the original charcoal canister when it happens.

When the canister becomes completely saturated with liquid gas, the evap system starts sucking in liquid gas directly into the base of the intake manifold whenever the throttle passes the advancer port (just very light throttle but not idle).
Engine won’t run when it’s sucking in gas like that and will stumble whenever the gas pedal is pressed.

Luckily with the original OEM charcoal canister, it can clear this problem naturally, given enough time, as the fuel will eventually drain out of the bottom of the charcoal canister and it will be cleared out.

But with this AC Delco canister- I can’t see any drain in the bottom of it. If that’s so, it would FILL TO THE BRIM with liquid gasoline during an overfill event and have no way to drain out.

Bottom Line:
NEVER EVER fill the gas tank to the top.
With these California gas prices I probably won’t ever be able to fill my 40 gallon tank again anyways so I guess I’m safe. Glass 1/2 full.
 
I've been looking into doing something on my non-existent evap setup. When I did my engine swap all the old evap stuff when in the trash and I never got around to doing anything. My main concern is dealing with the fuel tank vent that is at the firewall (having the vent work) and controlling liquid fuel should it come up the vent line (which it has), like on a steep descent where the fuel tank is at that point the high point of the fuel system. In my case I have a 5.7 vortec engine, currently with zero emission type gear.

I too have wondered how or is there an effective way to deal with liquid fuel that would come up the vent line.....into a presumably charcoal cannister or some type of vent tank. If the fuel does get into either...how does it come out.
 
Update - after hooking up the new canister I went for a 20 mile drive. As soon as I stopped the vehicle I hopped out and walked right around to the fuel cap and opened it up. I heard a bit of a whoosh. It was way reduced from before the swap though. It was probably about 5% of what it had been originally. Of course I was hoping for no sound whatsoever. I drove another 20 miles home and let it sit overnight before opening up the cap and I was happy to have it open without any sort of whoosh or pressure. I think that since originally I did not have a brass fitting to go from the tank line into the new canister and used that universal vacuum hose line adapter the hose line was reduced way more than necessary. I’m not sure what the Dorman reduces to but maybe like an eighth of an inch. I think that it probably was just taking a bit of time for pressure to equalize. So I found this brass fitting for the two different sized lines to adjust the tank line into the AC Delco canister As soon as I get a chance to go for a significant drive I’ll pop open the gas cap and let you know how it goes.
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Update - after hooking up the new canister I went for a 20 mile drive. As soon as I stopped the vehicle I hopped out and walked right around to the fuel cap and opened it up. I heard a bit of a whoosh. It was way reduced from before the swap though. It was probably about 5% of what it had been originally. Of course I was hoping for no sound whatsoever. I drove another 20 miles home and let it sit overnight before opening up the cap and I was happy to have it open without any sort of whoosh or pressure. I think that since originally I did not have a brass fitting to go from the tank line into the new canister and used that universal vacuum hose line adapter the hose line was reduced way more than necessary. I’m not sure what the Dorman reduces to but maybe like an eighth of an inch. I think that it probably was just taking a bit of time for pressure to equalize. So I found this brass fitting for the two different sized lines to adjust the tank line into the AC Delco canister As soon as I get a chance to go for a significant drive I’ll pop open the gas cap and let you know how it goes.View attachment 2950362View attachment 2950363
Update - just drove around and when I got home opened the gas cap and got a little sound. I’m guessing it’s as good as I’ll be able to make it and perhaps a nearly inaudible whoosh is normal. Can anybody with a normally functioning canister tell me if it’s totally silent immediately after a drive - such as pulling into a gas station and opening the cap?
 
When the gas tank is filled to the brim, (which should never be done) the EVAP system can (and will) suck liquid gasoline into the charcoal canister and actually set up a siphon for a while. Under the right circumstances, (over filled tank) liquid gasoline can be seen gushing out the bottom of the original charcoal canister when it happens.

When the canister becomes completely saturated with liquid gas, the evap system starts sucking in liquid gas directly into the base of the intake manifold whenever the throttle passes the advancer port (just very light throttle but not idle).
Engine won’t run when it’s sucking in gas like that and will stumble whenever the gas pedal is pressed.

Luckily with the original OEM charcoal canister, it can clear this problem naturally, given enough time, as the fuel will eventually drain out of the bottom of the charcoal canister and it will be cleared out.

But with this AC Delco canister- I can’t see any drain in the bottom of it. If that’s so, it would FILL TO THE BRIM with liquid gasoline during an overfill event and have no way to drain out.

Bottom Line:
NEVER EVER fill the gas tank to the top.

Could this happen in a truck that doesn't have a charcoal canister? Is the CC actually necessary?
 
Could this happen in a truck that doesn't have a charcoal canister? Is the CC actually necessary?
No.
It’s the EVAP emissions system that causes this problem when liquid gasoline flows into the charcoal canister.

The charcoal canister is an emissions component. It’s purpose is to collect gas tank vapors to be sucked into the engine later. Vehicles made in the 1960’s didn’t have charcoal canisters.

Also it traps gas tank vapors in the charcoal so that the car doesn’t smell of gasoline fumes when parked in a garage.
 
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No.
It’s the EVAP emissions system that causes this problem when liquid gasoline flows into the charcoal canister.

The charcoal canister is an emissions component. It’s purpose is to collect gas tank vapors to be sucked into the engine later. Vehicles made in the 1960’s didn’t have charcoal canisters.

Also it traps gas tank vapors in the charcoal so that the car doesn’t smell of gasoline fumes when parked in a garage.
Both the EVAP system and the charcoal canister are not used with a city racer carb, right?
 
The charcoal canister can be passive and not be plumbed to the engine intake. So it can be used with any engine setup.
Gas tank vapor line connects to one charcoal canister pipe, the other open to atmosphere.
 
Update - just drove around and when I got home opened the gas cap and got a little sound. I’m guessing it’s as good as I’ll be able to make it and perhaps a nearly inaudible whoosh is normal. Can anybody with a normally functioning canister tell me if it’s totally silent immediately after a drive - such as pulling into a gas station and opening the cap?
I have original equipment still and during the summer hot months it is pressurized when I pull up to the pump. During the cold months no pressure at all when I unscrew the gas cap. Just filled up yesterday and no pressure. On a really warm day however I had gas overflowing out the cap when full due to the pressure before. I got new gas caps just to be sure that wasn't the issue. It only happens occassionally but that also explains all the paint issues around the fill point. I see this same thing on so many cruisers. Pic below
 
during the summer hot months it is pressurized when I pull up to the pump

That’s because the charcoal canister internal check valve is clogged. They all are at this point.

Swap the two small hoses on the charcoal canister (Tank & Purge) and the pressurization will end.
The Purge pipe on the canister doesn’t have a check valve so vapors can flow freely.
No tank pressure.
 
That’s because the charcoal canister internal check valve is clogged. They all are at this point.

Swap the two small hoses on the charcoal canister (Tank & Purge) and the pressurization will end.
The Purge pipe on the canister doesn’t have a check valve so vapors can flow freely.
No tank pressure.
Funny thing is I did swap the hoses on the canister. Had the 62 in for service at Torfab and they swapped the hoses back to original stock position? I never asked why. I will switch them again.
 

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