How important is it?
should I try and hook it back up with my new motor and stuff?

 

The evap system controls and contains evaporated gas fumes from the gas tank and the carb bowl. You don't have to hook it up, but the gas tank needs to vent so you might get some gas smells under the hood. The vent line to the tank needs be open.

 

So it won't matter if I don't hook it up? I don't mind a little gas smell, I already think it is broken, last year I left my truck over three weeks with a quarter of a tank and came back and it was pretty much empty.

 

As far as the engine and how it runs, no it won't matter. If you do hook it up, then you have to be careful. The fumes from the charcoal canister have to be introduced to the engine at a controlled rate and at certain times to avoid drive-ability problems.

 

Sweet. Guess it's coming out too then.

 

The EVAP system actually does several things and the PCV valve is part of the system. In your case, I think you are talking just about the EVAP Canister and such?

When the engine is shut off, heat actually rises since the coolant flow stops. This causes fuel in the carburetor to evaporate, releasing fumes and such into the air.
The solution was to vent the bowl into a carbon canister. If you remove that, you'll have the fumes again. May not be a big deal to you.

The second thing the canister does is provide a place for the gas tank to vent. A vented cap allows air to enter the tank to compensate for vacuum inside. It is a one-way valve. The now pressurized air in the tank needs someplace to go, hence the vent line into the carbon canister. Leave this vent line open and, you guessed it, more fumes.

Once all the fumes and such go into the canister, it needs to be able to purge itself at some point. This is controlled either by the computer via solenoids or by vacuum via the PCV valve and a ported vacuum switch. In the later case, the switch only allows the canister to purge when the engine is at operating temperature and above idle speed; the fumes are then vented and burned via the PCV system.

Probably more than you wanted to know about EVAP but the bottom line is if you don't mind fumes, you can install a vented gas cap and leave the vent line open to the atmosphere.

Someone already said that, but I like to share..

I did a write up on the EVAP, in the sticky section as I recall.

 

Fumes need to be introduced when the engine is at operating temp and above idle. That's what the computer controls. In the case of earlier systems, it's controlled by a ported vacuum switch. In both cases, the fumes are introduced into the engine via the PCV system.

Elegant solution if you ask me..

 

Pretty sure a broken EVAP system wouldn't cause that. There is a vent line from the tank of course, but that's a lot of fuel.

If you remove the system, you need to leave the vent open. That is how it was done prior to the 60's or so and fuel didn't disappear.

I'd be thinking a leak or such

 

Ehh I'm not worried.

I'll use a vent line on the tanks already and keep it in the back of the truck to separate the tank vent and any fuel leak I might have.

I don't want to have a million vacuum lines for a system I don't understand. Thanks guys!