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evaporate control system (ECS canister) question
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Author:  pantseatflyer [ Mon Nov 17, 2003 6:28 pm ]
Post subject:  evaporate control system (ECS canister) question
After engine shutoff, about a minute later I get this seeping fuel leak around the base of the carburetor. I've taken the carb off about four times to adjust this and that, tighten gaskets, etc. I was about to give up on my carb and look for a new one.

Well, whenever I start pulling off hoses to remove the carb, I've always noticed there's a bit of fuel in the hose that runs from the base of the carb (just below the needle valve) to the ECS canister. The ECS canister has a charcoal filter that's supposed to hold gasoline vapors from the fuel tank and carb bowl temporarily until they can be drawn into the intake when the engine is running.

So, why would there be raw fuel in this ECS hose? Could this be causing my carb to leak due to pressure build up after engine shut off? Anyone mess with the ECS system before :?:
Author:  SlantDusterMike [ Mon Nov 17, 2003 6:51 pm ]
Post subject: 
i had a similar leak with my 1920 model holley carb, turned out to be the accelerator pump that was leaking, and gave all the same symptoms you've listed.

if its not that, then i have no idea what it could be.
Author:  relic-lover [ Mon Nov 17, 2003 6:51 pm ]
Post subject:  Are there two hoses ?
I work mostly on slants with no emissions so I might be off base here.
But I think the lower hose near the base of the carb is for PCV
(crankcase vent) hook up. For the ECS I thought there ought to be
a hose near the top of the fuel bowl (to pull fumes off into the
canister). These flow opposite ways - the PVC sucks into the carb
and the bowl vent on the fuel bowl should be pulling fumes
out of the carb through the charcoal canister by another vacuum
source hooked to the canister itself.

So is it possible the hoses got mixed up during the reinstall of the carb?

A manual for emission routing would be good here - what year - make
- model do you have?
Author:  pantseatflyer [ Mon Nov 17, 2003 7:18 pm ]
Post subject: 
there are actually two hoses that run from my carb to the ECS cansister. One is at the top (like you said) and the other is at the base, below the needle valve. The one at the base is supposed to take the emmissions out of the canister and through the intake when the engine is running. I guess it's possible that I have the two ECS swapped on the carb. How can I tell which ECS hose goes to the top and which goes to the base of the carb? I could always swap them and see if that fixes my leak, I suppose. I tried blowing through them and one of them is easy to blow through, the other not so easy.

I was also reading where the accelerator pump, when the engine is shut down, is supposed to get pushed upward by the spring in the pump shaft and open a vent to release the vapors (via the top hose) to the ECS canister. The problem could be that the vent isn't being opened after engine shutdown. Time to pull the carb a fifth time?

Will this madness never end?
Author:  Kermit Lucas [ Mon Nov 17, 2003 8:03 pm ]
Post subject: 
On the canister itself one of the outlets will read 'purge' (smaller nipple) and the other reads 'carb bowl'. Of course the one in the middle is from the tank. The one that reads 'purge' goes to the bottom of your carb.
Author:  Seis Inclinado [ Mon Nov 17, 2003 11:07 pm ]
Post subject:  Re: evaporate control system (ECS canister) question
Quote:
So, why would there be raw fuel in this ECS hose? Could this be causing my carb to leak due to pressure build up after engine shut off? Anyone mess with the ECS system before :?:
No, all the contrary...It's the same fuel that is leaking around the base of your carb because your needle valve is installed backwards...I think...(as you said in the other post)
:roll:
Author:  Eric W [ Tue Nov 18, 2003 1:02 am ]
Post subject: 
On top of the canaster you should have 4 nipples. Three large, one small. One is for the fuel tank vent line to hook to(actually a vaper tank inside the fuel tank). One is for the carburetor bowl vent. One goes to the PCV line. There should be a T fitting in the PCV line that the line from the canaster goes to. The purge line (small nipple) goes to a T fitting in the vacuum advance line, that goes to the ported vacuum on the carburetor. These fittings are marked on the canaster. This is the set up I had on my '72 engine. Don't forget, there is a filter on the bottem of the canaster. Fram sells them. Can't remember the part number, but it is in there book.
Author:  pantseatflyer [ Tue Nov 18, 2003 7:14 am ]
Post subject: 
actually there are three nipples on the canister and a short, larger hose coming off the back that's plugged. From the three, the middle runs back to the fuel tank, the purge nipple runs to the base of the carb and the bowl nipple runs to the bowl of the carb.

Question: What is that plugged hose on the back for?

I'll look for a replacement charcoal filter, since I doubt if it's ever been replaced.
Author:  Denny [ Tue Nov 18, 2003 8:59 am ]
Post subject: 
You mention taking the carb off 4 times to adjust it, but have you bought a rebuild kit & done that, yet? That's where you should start. Doesn't make sense to keep adjusting a carb which might have worn-out parts!
Author:  Denny [ Tue Nov 18, 2003 9:07 am ]
Post subject: 
[/b]Okay, now I see your other posts, where you did rebuild it but had the inlet valve backward. As somebody else pointed out, you could have damaged the rubber 'needle' & should replace it, at this point. [/b]


Quote:
You mention taking the carb off 4 times to adjust it, but have you bought a rebuild kit & done that, yet? That's where you should start. Doesn't make sense to keep adjusting a carb which might have worn-out parts!
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