opinions on vapor recovery system please
 

I am doing a bunch of upgrades & freshening this winter on my Camaro, and have now been able to fully see the plumbing of the evaporative system that was installed, I think by DSE when they installed the F.A.S.T. fuel injection system 4-5 years ago. (I bought the car last year), and am hoping some of those up on these things can help me figure out what to do with it.

The system...
There is a vent line going from the filler neck of the stainless tank to a small catch can under the trunk floor. Then a line from the catch can to the engine bay to a charcoal evap canister hidden under the fender. Then a line to the throttle body, drawing the fumes from the canister.
No valves to control the vacuum draw on the system. Pretty simple, but I just discovered a "T" in the vacuum line hiding under the brake vacuum booster, that can't be seen readily. So, there has been a 1/4" vacuum leak that the F.I. system has been compensating for all along! Also, it is drawing in unfiltered air, not a great idea.
A. I am wondering why the system was installed in the first place. The car was in Texas before I bought it...I could maybe understand if it was to be a California car, but I am unaware of any laws requiring such a system on a hot rod? Anybody else have such a system?
B. Should I leave the system operational, or abandon it? I am prone to leaving it (it ain't hurting anything, right?), but I am really bothered by the open vacuum leak, which I would think makes the actual draw on the system almost nil. (It can get all it's air draw from the open "T"). And it can't be helping the EFI system and the tuning of that.
C. If I plug the open "T", can/ will the vacuum cause fuel supply issues, and maybe even collapse the tank? That would suck (pardon the pun).

So I go back and forth, thinking of abandoning it, just plugging the vacuum line on the TB, and leaving it alone. I like the idea of capturing the fumes, eliminating fuel odors. And it seemed to work OK last year. Except I am really bothered by that vacuum leak! Do I plug that, or leave it?

Help please, this is really puzzling...and sorry for the long post.

Thanks!

Bill

Hey Bill -- what motor are you running?

look into a II Much fuel vent

It is a 534 c.i. BBC. .250" stroked 502.

There is already such a device, although not as attractive as the II Much piece. The hose you see is coming from the fuel tank. The picture doesn't show the hose coming out of the breather and going to the engine as described above.

http://i1113.photobucket.com/albums/...2bfbbb385b.jpg

It is the upstream part of the system I am puzzled by.



Thanks for the suggestion.

Bill

I would think you could just eliminate the "T" with a two-way connector and that would eliminate your vacuum leak and keep the functioning system. It sounds like a robust system, but that someone forgot to go back and replace a T that they used during mockup. Just a theory...

Thanks Jeff. That was my initial plan. Then a friend & I stared thinking about constant vacuum being applied to the fuel tank. As it has no other venting, I am fearful that could easily stall the car, or maybe even collapse the fuel tank. That negative pressure can be a powerful force.
AFAIK, the systems in our modern cars have a control valve to purge the charcoal canister at start up, then eliminate the vacuum during driving.

Anybody else have such a system?


Bill

There's no good reason to have a vacuum leak in any motor. A PCV is a CONTROLLED vacuum leak.... and that would be "tuned" along with the car. Plug it with your thumb and your RPM's will rise... but the point is that it's in the mix when the car is being tuned.

Now you have an uncontrolled vacuum leak. What happens to the motor when you plug it up?? Depending on your system (ECU) you may have to go back and redo the VE table as the MAP sensor may (should) see a completely different signal.


The system you describe is overly complicated given our cars - and their "smog" requirements. Lots of people have gas smell in their garages... and nobody likes or wants that. That is the type of HOSE used in the fuel system. Todays gas has all these new formulations and the gas fumes escape the old style hose rubber. This smell can be eliminated by switching the flex lines to Teflon braided hose.... or a rubber style hose that states it's okay for the new fuels.

I'd call DSE and ask if they remember doing this particular job - and why it was installed and maybe you can get a better understanding of what you have.

The more I think about it, I think the most logical route is to just not run the vacuum line from the charcoal canister to the TB. I will just leave that open to atmosphere, and plug the vacuum port on the TB. It will be interesting to see how much the A/F tuning changes, but as I am changing the heads/ cam/ comp. ratio, and re-ringing the engine, I guess we are starting from scratch anyway. I can always re-connect the last line & see what happens tune up wise if for some reason the need arises.

Thanks for the input!!

Bill