bczee

iTrader: (12)

Stealth.. good research.. post what you find ..!

LS1GMCTruck

iTrader: (2)

You really don't need the charcoal cannister system at all. Most swappers get rid of the whole system of lines, etc. You won't have any vapor smells either. Gar

stealth71

iTrader: (15)

How do you vent the tank then?

350SS

iTrader: (38)

Details...details

LS1GMCTruck

iTrader: (2)

With an open air vent hose, like a boats fuel tank/vent. You can run the hose up to the fuel fill/door area, to a fitting, to keep the dirt out...or not, it's up to you. Gar

76LQ9TA

iTrader: (1)

10033125 is the part for the gm breather. It is 1 psi pressure and vacuum.

chrisp3

350ss,

I'm in the process of cutting my factory tank to install an intank walbro 340.
I would agree with Stu Cool and LS1GMCTruck of running the vent line up to the filler door,and if you wanted to really do it right stick a cannister somewhere between,
BUT
why wouldn't just a venting fuel cap do the trick???.

76LQ9TA

iTrader: (1)

I installed the breather because the tap for this is already on the tanks inc. setup. If you install a vented fuel cap only, you may have problems when filling the tank. One of our older grain trucks had this setup. You had to fill the tank slowly or it would burp and spit gas out of the filler neck. With this setup air has to escape where the gas enters. I didn't have the charcoal cannister anymore or I would have hooked it up. Look under your car in front of the tank. I drilled a small hole in the sheetmetal brace and installed the breather there. It is higher than the fuel tank.

350SS

iTrader: (38)

The problem that I forsee is that when the gast tank is full, there won't necessarily be an air pocket above where the vent fitting is on the tank. In that instance, what happens? Is it going to force fuel out of the tank? I did my install a little differently than this one

but if the setup is recessed into the tank like this one, the vent fitting isn't goint to have air (fuel vapors really) around it to push out the vent, it's going to be submerged in fuel alot of the time. I should have taken pics of mine, but it will probably have the same problem even though mine is not recessed, it's flat on top of the passenger side of the tank. That's why I'm thinking that the factory vent system might be better since it has three vents (both corners and middle) so at least one will not be submerged in fuel hopefully.

chrisp3

well, what happened back in 1969 when GM thought it was a good idea to only use a venting gas cap?(as on my 69 camaro, no extra vents anywhere). maybe they did splash gas when topping off as 76LQ9TA said? maybe the filler neck is bigger than most gas(pump)nozzles and air escapes around the nozzle when filling the tank? Maybe most nozzles shut off automatically when the fuel comes up that high.

And most tanks that I have seen with the "Tanks Inc" setup have the vent recessed into the tank thereby submerging the vent into the fuel, at least while its full and at a stand still. But maybe due to the constant sloshing around of fuel(when your car starts moving), this will release any built up pressure as the air pockets in your tank are constantly moving around and happen to move across the vent line(s). So just put the vent at any high point on the tank, run it higher than the tank and there should not be a problem. I think GM went above and beond by installing 3 vents on your 72 chevelle, but I'd use them, (nothing to lose and everything to gain.)

350SS

iTrader: (38)

I agree with what you're saying and am hoping that the simplest solution is the best one, or at least works. Probably the best way to figure this out is by a little experimentation, and since I have my tank already setup with the Tanks Inc. purge setup and all the stock vents and fuel lines capped, I'll start by running it that way first and if it works, great. Hopefully I'll have this thing started up within the month and I'll make sure to update everyone on the situation.

Thanks everyone for the input on this, and don't hesitate to post up if we're overlooking anything

G-Body

iTrader: (4)

The vent on the top of the fuel tank has nothing to do with filling the tank, most vents on the top of the fuel tanks are 1/4" which is not enough to make a difference. On most old GM gas tanks the filler neck is set up so that as you fill the tank the gas flows down the bottom of the filler neck and the air flows out the top. If the tank doesn`t fill right and barfs up the gas if you fill it faster than the slowest setting it means that the filler tube was installed incorrectly in the tank. (don`t ask how I figured that out or how long it took )

The newer tanks are set up with an external 1/2" vent line running from the side of the tank right next to where the filler neck goes in to the top of the filler neck. If you get a crappy aftermarket tank that won`t fill you can add an external vent line on like this and make it fill properly.

gold00

Can some one tell me where the sending unit used in that tank set up was gootten from please.

Rodder

iTrader: (2)

I saw several comments in this thread about venting the tank to atmosphere without a check valve. DON'T DO THAT! Especially if you park inside an attached garage. The only venting you must have is to allow air into the tank. On our first gens, this is done by the vented gas cap, which has a check valve to only let air in and not let fuel vapor out. If you really want to vent the fuel vapor (so you don't get that first-gen whoosh when you take off the gas cap, and it's "good for the environment" too), you've gotta use a charcoal cannister with the purge setup. The purge setup is mandatory, otherwise the charcoal canister will get saturated with fuel. The other reason for a check valve on a vent is so you don't spill fuel all over the place when you're on a steep hill or in a rollover.

Heavy85

I know the thread is old but this is exactly what I need. I have an '02 fbody tank ... swapped in a '72 Datsun ... and am wondering if I really have to hook-up the tank pressure sensor and / or fuel tank level sensor for the purge system to work. I've got the lines to the purge valve into the TB hooked up just not the wires to the tank. So which tank sensors do I need to hook-up (if any) to get the evap system to keep pressures reasonable in the tank? This whole evap system seems really not well understood. The more I read the more theories I come across.

Thanks
Cameron

G-Body

iTrader: (4)

I didn`t hook either sensor up. I have not had any problems yet (30k+ miles) My PCM does not know the tank level or pressure and the EVAP purge valve opens when I start the car up. But if you have the sensors there anyway I would go ahead and run the wires, the factory put them there for a reason, if they could have done away with them I`m sure they would have.

Heavy85

Did you remove them from the program? I've read a theory that if you disable them then the system will still work but I dont have them disabled in the tune.

Thanks
Cameron

G-Body

iTrader: (4)

I have the SES light turned off for all them and the readiness settings are set to option 3 no report.

Heavy85

Ok so last question - are you using the fbody tank unmodified or something else or have you done anything to alter the evap system? If yours is similar to my '02 tank then this is good news as I can use it without hooking up the extra sensors.

Edit: So I'm confused again after looking at the schematic. There is an 'evap emissions canister vent valve' that appears to be solenoid operated back on the tank (pink & white wires). What does this do and does it need to be hooked up? The one by the TB is labeled 'evap emissions canister purge valve' and it is electrically the only thing I have hooked up in the evap system. I'm hoping to just get away with the purge valve mostly because I'm tires of wiring hell and it's not obvious with my configuration where everything else wires to without a lot of disassembly and tracing.

Thanks again
Cameron

Heavy85

bump ... G-Body or others any help here?

Thanks
Cameron