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Fuel tank vent line

Discussion in 'The Garage' started by towdriver80, Feb 26, 2005.

  1. towdriver80

    towdriver80 Registered Member

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    I was under the truck and spotted leaking fuel lines in the rear. I`ve replaced them several times since ive owned the truck. I hate salt!:mad: This time I`m using stainless tubing, found 50' rolls in the sizes I need. Definately not cheap. Right now the emissions are gone, no more charcoal canister. The fuel tank vent line runs to the front, joins the other vent lines and ends all the way up the firewall. Anyone know if I`ll have a problem if I just seal it shut at the tank? The stainless is expensive, but I don`t want any kind of a fuel starvation problem. I think the vent line with the fuel filler tube sould be enough, right? I cant just leave the tank vent line open at the tank, the truck runs alot of deep water. The truck is a 79K5, regular mechanical fuel pump, w/ supply and return.Truck avenger carb.
     
  2. dontoe

    dontoe 3/4 ton status GMOTM Winner

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    Did that to my '82 and when it got hot weather it built up pressure and blew off the fuel line, and alot of fuel until it depressurized itself. Doh!!!!!:doah:
     
  3. towdriver80

    towdriver80 Registered Member

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    If I went to the parts store and got a gas cap for a pre-emissions truck, would it would have some way to equalize pressure?
     
  4. mechted

    mechted 1 ton status Premium Member

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    the cap should be vented if its pre-emissions
     
  5. towdriver80

    towdriver80 Registered Member

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    Thanks. In NY anything older than 26 years is exempt from any emmissions requirements. I`m throwing a party.:D
     
  6. dontoe

    dontoe 3/4 ton status GMOTM Winner

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    Well, I drilled a hole in the cap. Worked for me!






    ...
     
  7. ntsqd

    ntsqd 1/2 ton status

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    Which is higher off the ground, the fill cap or the vent tube at the firewall? I'd use the highest one.

    FWIW, I put a plastic in-line fuel filter on the ends of my tank vents. The one on my Dune Buggy actually hangs out of the right front fender where it's visable behind the tire. I've had people warn me at stop lights that the my fuel filter is disconnected. :whistle:
     
  8. FWP

    FWP CRS

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    Bwahahah. that's hilarious:haha:
     
  9. towdriver80

    towdriver80 Registered Member

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    My gas cap and the vent on the firewall are only off by a couple of inches. I`m going to run the tubing and keep the fire wall vent. Somday I hope to run some kind of snorkel, and itl be easy to run the vent lines to it. This brought up a couple of good questions, though. Is the gas cap waterproof? When the pump sucks fuel from the tank, it has to get replaced by air. If it comes from the gas cap, it couldn`t be waterproof. If it comes from that vent line, I shouldn`t have run it with the other vent lines, I might be sucking crap from my tranny/t-case/axles into my gas tank. anyone know which one the make up air comes from?
     
  10. diesel4me

    diesel4me 1 ton status Premium Member

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    No Smoking!

    I had used an old gas filter as a way to vent a tank and keep crud out of the vent line--but be aware in hot weather the fumes coming out of the end of the vent line are exremely flammable,and having yours in the area of the wheels isnt a great idea--all it would take is someone to toss a ciggarette butt out the window and your tire to run it over and "WHOOF":weld: :yikes: --I'd put the vent up high under the center of the vehicle ,like the stock location....less exposure to outside spark sources...:crazy:
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Older caps are SUPPOSED to be vented easy, I checked some parts books, and caps for a 1973 truck were listed as being the same for a 1986. That is definitely incorrect. I couldn't find any that easily let air *out*.

    I've got an old cap which is vented easily "both ways", and it still builds up pressure. I'm not sure quite why, I haven't pulled it back off and checked the cause, but is obviously an entirely different design than the later ones, it has two seperate valves.
     
  12. dontoe

    dontoe 3/4 ton status GMOTM Winner

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    Both the '82 K-10s I had and my wife's '86 K-5 hissed/hiss when opened in hot weather. Definitely pressurized, but after I drilled the cap out on the K-10 it didn't do that anymore.

    The return line from the carb and the evaporative canister are the way it is normally vented. If I'm Thinking Correctly.
     
  13. ntsqd

    ntsqd 1/2 ton status

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    Yes, in a smog vintage the canister is the only vent. They want any hydrocarbons to be caught by the canister and not be allowed to escape into the atmosphere.
     
  14. towdriver80

    towdriver80 Registered Member

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    Thanks for all the info, guys! If that gas cap is waterproof, I`ll leave it alone. I`m going to re-run the vent line to the front, and keep it seperate from the axle/tcase/tranny vent line.
     

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