hey guys i have a tech question i am hoping some one will know. the charchol canister has a line running to it that i believe to be a vent line from the gas tank. well i removed the emissions and most electronic controls from the engine it is a carbbed motor and no computer controls on the engine what so ever. i'm not sure what this line does but there is no vaccuum running to it. i'm wanting to know if this is a vent line and if so will it hurt anything to just have it open with no vaccumms or the charchol canister attached?

thanks alot any info or comments would help

 

Justin86camaro,

The line you refer to is part of the emission system. Vapors from the tank are drawn into the intake and burned as part of the emission control system (which you have apparently completely removed).

At the moment it is still serving a purpose, venting. When your fuel level decreases the empty space must be replaced with air. Also any low pressure build-up will release though that line (it would normally go through the canister which you apparently removed). Because of the emission requirements in place during the manufacture of the vehicle the stock gas cap is a non-venting cap. The fumes are supposed to go into the canister, be purged/drawn into the intake, and burned.

I would not want that line "venting" into the engine compartment. I suggest that you purchase a vented fuel cap and then properly terminate/cap that line.

Sincerely,
Kurt

 

on my tank, I have a big white vent that is right off of the pump assembly, I also had a canister. If I can just get a vented fuel cap, I will bock off that vent line since I need to get a new one and they are $30 from the dealer.

 

thanks guys. i'll probly find a vented gas cap and cap the line.

 

so after you do that, you can just take out the charcoal canister?

 

Yes, Its only purpose AFAIK was to reroute the gas fumes to various vacume lines so it can be burnt in the engine.

I have remove the EEC on my car and as a short term solution for the vent line from the tank i have just let the hose dangle down in the fender where the vacume reserve is at, it "should" be far enough away from any sources of ignition so as not to make my car a ball of fire.

 

Yep! If you've removed all the other Emissions Equipment and Vacuum Lines, etc. it isn't doing anything anymore. HOPE YOU NEVER NEED AN EMISSION INSPECTION.

I hope you are not referring to the item that is located just over the axle on the driver's side? If so, I recommend leaving that in place. To the best of my knowledge that item functions as a "High-Pressure" relief. It's should not be in your way...I'd leave that one alone!

The fuel pick-up assembly has four (4) lines coming from it.
#1 Pickup
#2 Return
#3 Vent (to canister)
#4 High-Pressure Relief (Terminates Above Axle - Driver's Side)

Sincerely,
Kurt

 

that is what i'm talking about. Ok, well I guess I will shell out the $30 to get a new one. thanks.

 

I hope you are not referring to the item that is located just over the axle on the driver's side? If so, I recommend leaving that in place. To the best of my knowledge that item functions as a "High-Pressure" relief. It's should not be in your way...I'd leave that one alone!

The fuel pick-up assembly has four (4) lines coming from it.
#1 Pickup
#2 Return
#3 Vent (to canister)
#4 High-Pressure Relief (Terminates Above Axle - Driver's Side)

Sincerely,
Kurt [/B][/QUOTE]


Concerning the high pressure relief
Is there suppose to be a hose attached to that valve?
Mine is hangin down around the axle but it looks like
its missing a hose...just not sure..

Dave

 

Should look like the attached photo.

Kurt

 

excellent info kurt, thanks!
I'm in this spot right now.

So that 3rd line, the vent one, can be capped at the gas tank, then put on a vented gas cap eh? I'll have to check at a parts store now....

Do you have to disconnect anything at the fuel filler neck before dropping the gas tank? It doesn't look like anything is actually connected there...? (on my '82 car...)

 

Sonix,

It's gonna stink getting that tank out! I feel bad for you, but I've been there! Those of us with '82's, '83's, and '84's (I think?) have a one piece tank/filler neck. The later f-bodies were improved by making the filler neck removable. The later cars are VERY easy to remove the tank (not really.... but in comparison to the '82 they are!)

You should remove the plastic shroud that goes around the neck it's only a couple 9/32" screws up behind the driver's real wheel. Otherwise, you'll probably break it with all the twisting and turning as you get the tank out.

You should not have to pull the tank to cap that line. I'd just cap it at the corner of the tank where it comes around. It'll be a little tight but easier than pulling the tank.

If you're pulling the tank for another reason (i.e. Bad Pump) you might be able to find a better place to cap it. I'm a STRONG advocate of the block-mounted mechanical pump for ALL carb applications. However, that's just MY personal opinion.

WHY?
#1. They are cheaper (about $12 at AutoZone and Guaranteed for life! vs $50+ for the regulator + The Electric Pump)
#2. Less complicated than plumbing a pressure regulator.
#3. Easier to change when they go bad (30 minutes for a mechanical vs. several hours and yet another tank pull for a electric pump)
#4. Not prone to electrical problems and re-wiring requirements if you've eliminated the ECM.

The ONLY drawback IMPO is the INITIAL tank pull.... Once complete, you should NEVER have to pull the tank again!

Sincerely,
Kurt

 

oh yea, my pump works fine, but i'm basically doing a "frame off" restoration, so i'm painting the underside to eliminate rust (lots of it). I've already got the rear axle out, upgrading, and new suspension. So the fuel tank is basically on it's own up there.


alrighty then, thanks for the heads up, looks like another one to add to the list of "not quite perfect in the first year of third-gen", such as the headliner/seatbelt slot....

 

At the drvr side rear axle is not a pressure relief of any sort.

Its name by GM is a fuel tank vent valve.

Its a misnomer though

It only lets fresh air in to make up for the fuel used.

Otherwise the tank would suck itself in.

So it is a one way check valve to let air in, but nothing out.

later
Jeremy

 

3.8TransAM,
Thanks for the clarification. I've been told so many different things about this item it's unreal. Several folks had told me it was a relief, and since that was the "Most Common" answer when I was trying to figure it our last year, I assumed that was correct. I did state "To the best of my knowledge" in my previous post.

I personally recommend leaving it alone since it shouldn't be in anyone's way. If you are correct, and I assume that you are, it would be a very bad move to remove it. Do you agree?

Kurt

 

So if you buy a vented gas cap, anyway to buy a locking vent cap?

 

Since this was Necromanced, I thought i'd put in my .25.
My 88 also had a one piece tank and filler neck. Major PITA.

 

I see information posted on that check valve coming off the sending unit all the time that is wrong. This is word for word from the gm service manual for a 92 camaro... the fuel tank vent valve, located in the left rear of the vehicle by the fuel tank, is a pressure/vacuum relief valve. When fuel tank pressure exceeds 5.5 - 7.6kPa (.8 - 1.1 psi) the valve will open allowing tank pressure to bleed off. When the fuel tank is in a vacuum, the vent valve will open (between .88" - 1.9" Hg) allowing fresh air to be pulled in. If you have the service manual for a 92 camaro, it is on page 6E3-C3-2. I haven't tried it myself, but in theory you should be able to pull off the canister and cap that line period. No vented cap should be needed at all.

 

92RS is right- the valve does both functions- vacuum and pressure relief. And, by the way, those are the EXACT same 2 functions that a vented gas cap does. That's why 3rd gens have solid gas caps, not vented ones like many other cars use- the functionality is already built into the separate tank vent valve.

 

So does that make it a backup to the line that goes to the charcoal canister?

 

Thats the way I interpret the manual. The main vent is the charcoal canister line which has a fuel vapor control valve. It takes 5 kPa to open that valve (it takes 5.5 - 7.6 kPa to open the tank vent valve). So I guess in the event that line gets clogged or the canister stops working, the tank vent valve will open to prevent the tank from bursting. I don't really see a negative to just plugging that line as it only takes .5 - 2.6 more kPa to make the tank vent valve open anyway.