info for round evap's

[myraley]

I just wanted to post this info, so no one else would need to do the research like I did. If you want your evap charcoal canister to work (the round kind), here are some photos and some info. If your have a quadrajet carb that does not have a vent hose from the fuel bowl, you will want canister # 7030605. It has three hoses coming off of it. One to a PORTED vacuum port on the carb, one to the PCV and one to the fuel tank. The vapor comes from the fuel tank, sits in the canister until the ported vacuum is applied and then enters the PCV.

 

[myraley]

So that should work for the, what are they called, the 4mv Quadrajets? The mid 70's. But what if you have a late 70's or early eighties quadrajet? The M4m series? the main difference in this area is how they vented the fuel bowl. On the later ones, there is actually a hose connection to get the vapors from the fuel bowl. From what I understand, it also helps prevent hard to start situations when the engine is hot, but thats a carb thing, not a evap canister thing. Anyway, here's a photo of the 5 hose evap canister.

 

[myraley]

The 5 hose canister is part # 17060868, and Napa has it listed, but was unable to order it, so I went to Star auto, and they cross referenced the # with the number from Napa. It was pricey, maybe $85? Ok, so on this one, the top left hose is small, goes to ported vac from the carb. The hose below it goes to the PCV. The small hose on the top right goes to manifold vacuum, and the hose underneath it goes to the fuel bowl. The middle hose goes to the gas tank.

 

[myraley]

What that does is that the top left hose goes to ported and OPENS the line to the PCV when there is ported vacuum. The top right hose to manifold vacuum CLOSES the line from the fuel bowl when there is manifold vacuum. The tank hose is, uh, the tank hose. Its open all the time. To figure this out, I cut off the ported cap so I could see the rubber seal underneath that opens the PCV line when vacuum is applied.

 

[myraley]

Until I did all of this, I could not understand why each hose went where it did, or how it worked. Hopefully, if you dont have this connected in your truck, you will see that there is no downside to having it connected, it can only help your fuel tank and fuel bowl work better and as they were designed. Also, thanks to Brian in Morgan Hill who helped me get started on this a long time ago. For those who are still convinced that all smog stuff is bad, and that this is better unconnected, I dyno'd my truck, and it made no difference whther it was connected or not in any of the numbers on horsepower or torque. That said, I cannot vouch for anthing concerning EGR, or any other smog stuff, but the evap canister is a good thing.

THANKS TO ALL CK 5 MEMBERS FOR ALL OF THEIR KNOWLEDGE! I am nearly done fixing previous owner mistakes. Only took two years and days spent searching the posts here.
Eric

 

[Kenny78]

I would like to say Thank You. I feel the ame about this system but have the 5 line tank. Cruised the internet for a little while but decided I had better things to do at the time. This will go on my to do list now

Appreciate it!!

 

[bp71k5]

Yea, nice. My tank vent isn't working as good as it should and I've been considering hooking that thing back up again.

 

[dyeager535]

Appreciate the posts and info. I didn't realize how beneficial these were until after I had removed the one in my current truck. Next time around it's getting hooked up!