77 Evap Canister Hookup

[gjacobs101]

Hello,
I have my new 32/36 carb in and I'm trying to figure out what to do with the under hood canister. I have poured over the forum data. The underhood canister has a top and bottom connection. I presume top is "in", bottom is "out". I think the idea is fumes in the top, with vacumn pulling out fumes into the intake manifold. For my 77, I now have a hanging tank vent and canister in/out lines. From what I can gather from other posts:
- Option 1: Get special fuel filter with three connections. Tie tank return line to extra fuel filter line. Never seen one of these, not sure where you can get one.
- Option 2: For my 77, I now have a capped off intake manifold vacumn line where an idle?? solenoid connection was made. To connect the canister, I would connect the "in" to the tank return line, and the "out" to where the idle solenoid vacumn line used to be. I have also read that a flow restrictor is needed here.

Maybe I am suffering from to much information. Could someone provide me some clarification? From what I understand, its a good thing to leave the canister in, but I don't want to create a vacumn leak and I 'm trying to simplify as much as possible.

Thanks in advance
-George

[gjacobs101]

Bump. Any folks have suggestions?

Thanks
-George

[baltobernie]

As you can see, you're not alone. I'm still not happy with my results, and am looking for an alternate 3-way valve for the trunk. Sorry about the bad photo; busted a link somewhere.

http://www.fiatspider.com/f08/viewtopic ... =+canister
http://www.fiatspider.com/f08/viewtopic ... =+canister

[majicwrench]

Whatever vacuum you attach to the cannister should be ported. You should nNOT be sucking fumes from canister at an idle.
Genericly how a canister works is: fumes from the tank collect in the carbon. When you shut car off, then fumes from the float bowl collect in the carbon. THERE HAS TO BE SOME SORT OF VAlvE THAT PREVENTS FUMES FROM THE FLOAT BOWL REACHING THE CANISTER WHEN ENGINE RUNNING!!! ( called a bowl vent valve in old Ford lingo) THen when engine warm and above idle, ported vacuum to cannister pulls fumes back out of canister and burns em in engine. This should not happen with engine cold, and should not happen at an idle.

Once you change carbs, really tough to get that kind of stuff working right again.

[gjacobs101]

Many thanks for the replies. Thats the best description of the canister operation I seen. Unless I can find one of those 3 port filters to hook up the tank vent, I'll go with removing the canister. Does the under hood canister handle tank vapors too, or is there canister for that?

I recently fixed rotted fuel lines that caused me to be sitting a pool of fuel, so I want to make sure my fuel system is safe.

-George

[baltobernie]

It is my understanding that the can in the trunk separates liquid gasoline from gasoline vapor, and the canister in the engine compartment captures and delivers to the carburetor vapors from both the fuel tank and carburetor bowl. I saw a block diagram on Google back when I first started overhauling the fuel system; should have saved it. It clearly described universally where all the hoses go on virtually all cars.

I also believe that one can capture and reuse vapors from the Spider fuel tank with the OE setup, even if the OE carburetor has been replaced with a non-sealed (open ventilation) carb(s). YMMV.

[So Cal Mark]

the only thing you have to do is cap the vent line that used to attach to the float bowl. the vent line from the tank should still be attached to the cannister, and the vacuum line can attach to the carb base

[geno58]

Is it nessisary to keep the Canister? I was looking at some of the Engine pics on one of the other threads, and it appeared most where not still using the Canister. Whats the scoop?

[gjacobs101]

After further examination, I also see a bottom line coming out of the canister. It appears to run back through the firewall by the transmission.
From what Mark says:
- Top port canister, to fuel return. Fuel return has one way valve in line. I believe this should only allow the canister to pull from the tank
- Middle canister port to dizzy vac port on carb
- Bottom port canister ???

How about the previous post that the canister vacumn should only be active at idle?

Thanks
-George

[majicwrench]

There should be NO VACUUM pulling thru the canister at idle, nor when the engine is cold. In other words, with engine running at idle, if you pinch off any lines goign to canister, idle should not change. I don't have a Fiat with a canister so can't help you specificly with the lines

Top port canister, to fuel return????? Maybe I missed it but did somebody say that?? Nothing with canister should connect to fuel return.

[So Cal Mark]

nothing to do with the cannister and fuel return, they are two separate systems. If you're installing a dfev carb you will do without the fuel return. The line in the bottom of the cannister is a vapor line from the tank

[gjacobs101]

I think I have it now:
- Plug tank return line. Eg. Metal line that runs alongside fuel line
- Plug canister top connection. This is connection that used to run to the carb float bowl.
- Connect middle canister connection to vacumn port on carb.
- Bottom canister connection back to tank stays the same.

Please let me know if this is correct.

Thanks
-George

[majicwrench]

Make darn sure "vacuum port on carb" is ported vacuum, no vacuum at idle!!!!!!

[gjacobs101]

Not sure what ported vacumn is. I guess I will leave the canister unconnected, not sure what the correct connections are.

-George

[So Cal Mark]

ported vacuum comes from a port above the throttle plate. There is no vacuum at the port with the throttle closed. The only port on the dfev is ported vacuum. The other source is manifold vacuum and is normally drawn directly from a port on the manifold