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Fuel venting into car?

6K views 22 replies 10 participants last post by  qbui 
#1 · (Edited)
I know I've read a thread about a year ago where the person said after he added a vent for his fuel tank, his garage stinks of fuel comparing to before the vent but can't seem to find it in search. I have a similar issue where after I installed the EFI fuel tank and vent the tank to the rear passenger wheel well, every morning I get into the car, I smell fuel vapor until I roll down the window or put the top down. I do keep the rear windows cracked a bit and that could be the entry point. Also I park next to a wall in a community garage so the fumes could be bouncing off the wall and getting into the cabin. When I park my car out in the hot sun at work, I get in and there's no smell so it's probably not coming from inside since the sun would make the fumes worse if coming from inside, so could it be the vent being sucked into my cabin from the rear windows being down?

Actually, yesterday when I drove my car to lunch and sat at an outside table near my car. I can smell the fumes from my car. I did just filled up yesterday if that makes any difference. Anyone else with a vented fuel tank noticed the extra odor of fuel?

Thanks!
 
#2 ·
You should not have a vent to the atmosphere. You don't need a vent other than a vented fuel filler cap, which has a one-way valve to allow atmospheric air IN, and a spring loaded safety valve to allow expansion to escape if the pressure gets too high. The only purpose for modern fuel tank vents is to collect the expanding vapors, send them to a charcoal canister, and via a purge valve into the intake stream.
 
#5 ·
You should not have a vent to the atmosphere. You don't need a vent other than a vented fuel filler cap, which has a one-way valve to allow atmospheric air IN, and a spring loaded safety valve to allow expansion to escape if the pressure gets too high. The only purpose for modern fuel tank vents is to collect the expanding vapors, send them to a charcoal canister, and via a purge valve into the intake stream.

Kelly, Bart is correct. He did mention having a vented cap which will do exactly what needs to be done. OP's EFI conversion doesn't need a close loop EVAP system, or any other type of vent.
 
#3 ·
Bartl, are you saying I didn't need to purchase the Tanks Inc vent valve like they suggested? Could they be trying to make a few extra bucks from people who buy their tanks :)

I'll plug the vent valve once I get things sorted out so not to pitentially introduce another issue to the mix.

Thanks Barlt!
 
#4 ·
Bart is incorrect in this instance - you DO need the vent valve for your EFI'd motor. Trust me on that one. When you drive around without one, your tank will pressurize like no tomorrow. Been there, done that.

As far as the fuel smell goes, is it raw fuel? What materials did you use for your fuel lines? Do you have any rubber in the system? How is the hose for the vent routed? I just recently went through my lines for this exact reason and have eliminated all of the raw gas smell from my car that came from degraded rubber lines (rated for EFI pressures, but not for today's ethanol fuels apparently) and an improperly routed vent hose.
 
#14 ·
Bart is incorrect in this instance - you DO need the vent valve for your EFI'd motor. Trust me on that one. When you drive around without one, your tank will pressurize like no tomorrow. Been there, done that.
Why does the tank pressurize? Fuel gets pumped out, some gets used by the engine and the remaining fuel gets pumped back to the tank. What's pressurizing the tank???
 
#6 ·
I suppose if you converted to that type of gas cap (which I'm unfamiliar with) then that would be correct.

But stock vintage gas caps are not vented enough to prevent the tank from pressurizing. The instructions for most TBIs specifically state this. I've tested it thoroughly on my own EFI'd car with impressively disastrous results with a blocked vent. The problem is not just that the tank will develop a vacuum (in which case you need to let air in, as Bart said) but also that the tank will pressurize (in which case you need to let air out). Mine will build enough pressure that I can hear it whistling over the sound of the exhaust.

With a vintage gas cap you do need a vent... it's really not hogwash ;) The one sold by Tanks Inc. (which is the one I have) has a check valve in it so it's not just an open ended hose if that's what you're thinking of.
 
#11 ·
Well, that's good to know.
 
#8 ·
Nope, no strong gas fumes here.

I did have very strong gas fumes when I had braided SS rubber fuel lines. After swapping to teflon, no more raw gas smell at all in the garage. Still smells like exhaust when I pull in, of course, but doesn't smell like anything after sitting for a while :)
 
#9 ·
I am running FAST EFI and Tanks Inc EFI tank ..even though I am using a repro GT350 cap which is vented I still ran a vent line to the supplied rollover vent valve I installed in the passenger wheel well. I only have about 50 miles on it so far and the only whiff of gas fumes are around the gas cap and filler neck at rear of car. I'm somewhat lucky that the Gulf station in Fredericksburg has premium unleaded with no ethanol. Won't help when I'm traveling... so since all my FAST EFI lines are rubber I'll face the same issue as Kelly with seeping gas lines. If Scott Drake gas caps don't have a vent I may get one of those and solely rely on the Tanks Inc rollover vent valve.

here's a link to Tanks Inc.

Fuel Tank Venting
 
#10 ·
Thanks Kelly! Have to check on the outside to see if there are any leaks around the buldheads.

Weikelrk, I have the same TI vent valve and installed it in the same location and per TI's instructions. We do have ethanol here and it's been warm out this week.
 
#15 ·
I was going to purchase that Spectra Premium tank too but couldn't find any info on the tank, even from Spectra's website so I decided against it. Would have been a little easier to install. I've read that people vent from the filler neck so you can look into that if you need to vent.
 
#18 ·
Fuel probably wants to leave a presurized tank and head towards your injectors quicker I assume.

How much pressure do they have?
 
#19 ·
2 ways a tank can pressurize
1. as I mentioned ambient temp.
2. as the fuel circulates in closed circuit as an efi system it will heat the fuel up some as it circulates around the fuel rails and back to tank, the electric pump itself will cause the fuel to heat up some all of this will cause the gasoline to expand and creat pressure. Newton makes a 2 way check that will allow a tank to vent if it needs to or take air in if a vaccum should occur.
 
#22 ·
Kelly is right, I have a 95 motor and efi in my 65 with a stock cap. I had problems going from Bakersfield to Lake Tahoe. I welded a fitting into the top of the fill tube, ran a 5/16" hose out the floor behind the rear pan. No more problems and no gas smell. By placing the vent high on the fill tube it is 8" above the gas.
 
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