FITech Installation - Vent Line

[NC_John]

I'm starting the FITech install on my farm truck tomorrow. One thing I've been thinking about is the instructions being so adamant about running the command center vent line back into the fuel tank.

Since our trucks are pre-emission and don't control/scrub the gas fumes from the tank, I can't see this as being critical. I suspect the directions mandate running the vent back to the tank for retrofit on newer vehicles that may have controlled venting/charcoal canisters etc....

If the gas tank vents straight to atmosphere anyway, what's the point running the vent line back to it? I think I am going to run mine down the frame away from heat/exhaust/any sources of ignition and just let it go. I'm also thinking about getting an evap canister from a newer vehicle and hiding that underneath but am not sure how long it will stay effective.

Thoughts? Is there any other reason why they want to do this? In case the electric pump doesn't cut off it will return the fuel back to the tank?

[dirtyjim]

part of the reason they want it vented back to the tank is because the cc has a float in it to control the fuel level inside the cc. if that float get trash in it and sticks it will be venting fuel instead of vapor

[NC_John]

Originally Posted by dirtyjim

part of the reason they want it vented back to the tank is because the cc has a float in it to control the fuel level inside the cc. if that float get trash in it and sticks it will be venting fuel instead of vapor

That was one of my theories. So where do I return it to on a '70 tank? Part of the appeal of this setup was no need for a return line.....

[Gromit]

I've read - (I believe on this site) - that others have vent it back to the driver's side upper tank vent. But this would require the California version of the 1970; so you would need to order one of those replacement Evaporative Emission Control "EEC" type tanks - but at least those tanks seem to be readily available.

Here is a photo of the vent I'm referring to - it is the first year of the EEC and it was in California vehicle starting in 1970.

The I.D. of the vents is 5/16" and the Fuel Supply lines are same as non-EEC 3/8"

I am not saying that this is optimum or that I am recommending it but just that you might consider checking further to see who has done it that way. If you had that 1970 EEC tank you may also need to install vent lines and a charcoal canister if you want all the hookups to be as stock.

[Nitis]

Would it be possible to use a 72 automatic sending unit they have two lines? Lots simpler than swapping the whole tank not to mention cheaper

[Gromit]

That idea sounds promising to me Nitis - I'm not familiar with the other years but here is a photo of the 1970 EEC sending unit for what it is worth.. Mainly to rule it out I suppose but just to show the configuration. The vents are higher up and on each side of the tank.

An observation in favor of a sending unit modification (or retrofit with a later year) like Nitis suggested is that the height of the sending unit is lower than that if the upper drivers side tank vent - and importantly perhaps even with or slightly below the level of the carburetor fuel rail.

[Nitis]

I am thinking since it is a VENT and not a return this should work just fine

Quick search said some people didn't like the idea of the smaller line when running returns for TPI and possibly LSx setups

My plan is to use this if I can get my engine soon then I will relocate the tank to the rear of the truck when it comes time for body and paint

[NC_John]

Well this job just got a lot more complicated. With plans to eventually relocate the tank under the bed there is no way I am buying another in-cab one just for this.

I guess I'll have to see what kind of PITA it is going to be the pull the pickup and sending unit from the tank and see if I can modify that bung fitting to take a return line. I'll be pissed if I have to pull my seat since it was just out a little while ago for the carpet install.

Why do these guys say no return line needed when you obviously need one?

[Nitis]

if your seat will fold forward no problem if not yeah you will have to pull it

for $40 I would just order a new sending unit with the vent already inplace but maybe you got the time tools and skills that I don't

Good luck keep us posted

[NC_John]

Originally Posted by Nitis

if your seat will fold forward no problem if not yeah you will have to pull it

for $40 I would just order a new sending unit with the vent already inplace but maybe you got the time tools and skills that I don't

Good luck keep us posted

If I can get just the sending unit, I'll go that way. Yeah, I'll let you know.

Thanks for the comments/ideas.

[Nitis]

Originally Posted by NC_John

If I can get just the sending unit, I'll go that way. Yeah, I'll let you know.

Thanks for the comments/ideas.

just need one for a 72 with automatic should have 2 ports one 3/8 one 5/16

[NC_John]

Originally Posted by Nitis

just need one for a 72 with automatic should have 2 ports one 3/8 one 5/16

I looked them up on the truck and car shop site (they have a location fairly close by) and saw the different pn's for auto/manual. What's the difference between them?

[Nitis]

manual only has one port

you need the one for 72 automatic

[Gromit]

My '70 bench seatback will fold forward if I remove one of the bolts (on each side) of the back where it attaches to the bench seat bottom. Then slightly loosen the bolts in the front to help it pivot without binding the seatcover.

[TA1968]

Check this thread out member Big Kev-O did to his sending unit post # 33

http://67-72chevytrucks.com/vboard/s...=688342&page=2

[NC_John]

Originally Posted by Nitis

just need one for a 72 with automatic should have 2 ports one 3/8 one 5/16

I got a 72 auto setup today (lousy counterpart junk- I think I'll hang on to my factory one for a while). It is set up for two hoses, and no hardlines. The fuel supply line on my 70 is hard pipe. Did they change it in 71/72 or is the repop part just cheap?

[Lattimer]

I've been thinking about running the vent that way myself, but when I discussed it with FI Tech they said it wasn't good because when the tank is full the vent is below the fuel level.

I'm still holding off ordering anything because I haven't come up with a good idea on the vent. My in cab tank is new, I refuse to relocate it, and I don't have EEC to tap into.

[NC_John]

Originally Posted by Lattimer

I've been thinking about running the vent that way myself, but when I discussed it with FI Tech they said it wasn't good because when the tank is full the vent is below the fuel level.

I'm still holding off ordering anything because I haven't come up with a good idea on the vent. My in cab tank is new, I refuse to relocate it, and I don't have EEC to tap into.

It's just a little stub down into the tank, hardly an inch or two long.. I have to look at it in its mounted position but the tank would have to be 100% full if not darn near overflowing for it to be below the fuel level. It'll work fine for me- I don't fill my tank up to the neck since it tends to spit out the cap and run down the bedside during "spirited driving."

The bad news for me is my fuel lines from Jegs are in fedex purgatory. They were delivered yesterday but we don't know where. Not here. &$#%!

[Lattimer]

Originally Posted by NC_John

It's just a little stub down into the tank, hardly an inch or two long.. I have to look at it in its mounted position but the tank would have to be 100% full if not darn near overflowing for it to be below the fuel level. It'll work fine for me- I don't fill my tank up to the neck since it tends to spit out the cap and run down the bedside during "spirited driving."

The bad news for me is my fuel lines from Jegs are in fedex purgatory. They were delivered yesterday but we don't know where. Not here. &$#%!

I modified my cap, so it seals well and I don't get any leakage even when completely full, so I always fill it until the nozzle clicks off.

When full to that level, the vent would be under about 2"-3" of fuel.

I still think it might work, since there is about 8 psi of fuel pressure from the mechanical pump in the FCC to push the vapors. Just not sure I'm willing to risk spending all that money just to vapor lock the system.

[Katrina/10]

I tried using that extra port on the later model sending unit as a vent, and it didn't work. It is most definitely submerged when you have a full tank, and will push lots of fuel out that line with a non-vented cap. Those are supposed to be hose clamp fittings.

[NC_John]

Originally Posted by Lattimer

I've been thinking about running the vent that way myself, but when I discussed it with FI Tech they said it wasn't good because when the tank is full the vent is below the fuel level.

I'm a bit annoyed at FItech at this point. Every piece of literature you need says "NO RETURN LINE NEEDED." WTF is all this then? It won't work on our earlier stock tanks without some kind of modification. It's misleading if you ask me.

[Lattimer]

Originally Posted by NC_John

I'm a bit annoyed at FItech at this point. Every piece of literature you need says "NO RETURN LINE NEEDED." WTF is all this then? It won't work on our earlier stock tanks without some kind of modification. It's misleading if you ask me.

Its not a return, its a vent. So they can get away with it.

As much as I like their setup, I found them downright rude when I was emailing them.

[NC_John]

Originally Posted by Lattimer

I modified my cap, so it seals well and I don't get any leakage even when completely full, so I always fill it until the nozzle clicks off.

When full to that level, the vent would be under about 2"-3" of fuel.

I still think it might work, since there is about 8 psi of fuel pressure from the mechanical pump in the FCC to push the vapors. Just not sure I'm willing to risk spending all that money just to vapor lock the system.

I bet you could pretty easily modify the "vent" tube into the tank with a piece of tubing bent into a "u" and turned up to get it higher. Could probably use a small piece of rubber hose and some clamps as a coupler to add the tubing. If done correctly that would get it higher in the tank. I'll check it out this weekend when I get back to work on it.

[NC_John]

Originally Posted by Katrina/10

I tried using that extra port on the later model sending unit as a vent, and it didn't work. It is most definitely submerged when you have a full tank, and will push lots of fuel out that line with a non-vented cap. Those are supposed to be hose clamp fittings.

Well, like I said, I don't fill my tank right up to the top and I might even do that little mod I just mentioned to Lattimer.

I am not changing the tank to a newer in-cab one just for this. When I go shortbed, all this crap is coming out of the cab and going out back anyway. I'll likely get an EFI ready tank with a submerged pump too to get rid of the command center and the clutter it adds under the hood.

[NC_John]

Originally Posted by Lattimer

Its not a return, its a vent. So they can get away with it.

As much as I like their setup, I found them downright rude when I was emailing them.

Well, hopefully I won't need to deal with them directly on anything and the juice is worth the squeeze for all the time, money and effort to do this.

If all goes well and I don't hit any more bumps, I hope to have it running this weekend. The truck is laid up in the "premium (easy access)" bay in my garage, just stuck there, in the way right now. It needs to move!