FITech Installation - Vent Line
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? |
Re: FITech Installation - Vent Line
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
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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. |
Re: FITech Installation - Vent Line
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
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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. |
Re: FITech Installation - Vent Line
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 |
Re: FITech Installation - Vent Line
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? |
Re: FITech Installation - Vent Line
if your seat will fold forward no problem if not yeah you will have to pull it
for $40 I would just order a new sending unit with the vent already inplace but maybe you got the time tools and skills that I don't Good luck keep us posted |
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Thanks for the comments/ideas. |
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manual only has one port
you need the one for 72 automatic |
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My '70 bench seatback will fold forward if I remove one of the bolts (on each side) of the back where it attaches to the bench seat bottom. Then slightly loosen the bolts in the front to help it pivot without binding the seatcover.
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Re: FITech Installation - Vent Line
Check this thread out member Big Kev-O did to his sending unit post # 33
http://67-72chevytrucks.com/vboard/s...=688342&page=2 |
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I've been thinking about running the vent that way myself, but when I discussed it with FI Tech they said it wasn't good because when the tank is full the vent is below the fuel level.
I'm still holding off ordering anything because I haven't come up with a good idea on the vent. My in cab tank is new, I refuse to relocate it, and I don't have EEC to tap into. |
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The bad news for me is my fuel lines from Jegs are in fedex purgatory. They were delivered yesterday but we don't know where. Not here. &$#%! |
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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. |
Re: FITech Installation - Vent Line
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.
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As much as I like their setup, I found them downright rude when I was emailing them. |
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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. |
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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! |
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