bought this to fix fuel drain back problem

Fuel and Air Systems

  1. seabee

    seabee FABO Gold Member FABO Gold Member

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    Yep. For Fs Sake! The guy went out of his way to try something and took the time to share that info with all of us. This sight is a virtual goldmine of how to's and have done's. Not a pissing contest.
     
  2. EL5DEMON340

    EL5DEMON340 Well-Known Member

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    After sitting for several days I have to crank my engine for about 5 seconds then pump it 3 times and it starts, my problem is the fuel evaporating out of the carb after a hot shut off, and ethanol fuel. I don't think a carb will empty through the needle and seat. Your problem having to crank that much might be a tank not vented correctly, pickup sock clogged, or a faulty pump valve, but if the valve is working its probably a bandaid for one of the problems I listed. Also if your going to keep that in the line make sure you have a screen filter at the carb inlet, if the check valve fails and a needle sticks open there may be a fire risk.
     
  3. Gen2Cudas

    Gen2Cudas Well-Known Member

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    I will weigh in. I have bought your do-dad off Ebay, and am waiting for it to show up so I can install it inline on a Slant Six. Thanks for the tip. I have been having all the same problems you have mentioned on not one but two of these beasts: one an Edlebrock fed 318 with new everything from the fuel pump to the carb, original parts back from there. . . soon to be new everything from the tank forward. . . and one that IS new everything from the thank forward to a Ball and Ball single with SlantSix Dan's mods done, feeding said Slanty. Both cars would appear to lose prime after about a week's sitting, by whatever voodoo, and need excessive cranking to get the fuel filters and bowls full enough to start. And yes, it seemed to begin about the same time as E10 showed up as my only choice for gas. Most of my ideas as to why have appeared here already, so no need to rehash. I was getting ready to build a priming pump set up when this thread appeared. . .and, I too will let ya know if it is effective for me as well. Thanks again.
     
  4. toolmanmike

    toolmanmike Moderator Staff Member FABO Gold Member

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    Did it work?
     
  5. bOb shingler

    bOb shingler Well-Known Member

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    /\ x2
     
  6. adriver

    adriver Blazing Apostle

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    It's a check valve. It's cheap. It's easy. It probably works.
    It can't hurt unless people are concerned about racing.
     
  7. 340-4spd

    340-4spd Well-Known Member

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    I've used one of these on my old mechanically injected Cummins for years with great success. That engine is particularly problematic in this regard because once air gets in the lines you have to manually bleed the injectors, which is rather a large PITA. Even the tiniest imperfection somewhere in the fuel system seems to be enough of an issue to cause bleed back without showing a leak or any other abnormalities except the resultant inability to start due to air getting in the injection lines.

    I am putting one on the Mopar now too. I can confirm the symptom and behavior as described. You would think that technically this drainback is not possible, but it is. I was looking at the clear glass filter I have installed in the fuel line just the other day and it was dry after sitting for about a week. I cannot imagine how it could be evaporating three feet back into the line from the carb.
     
  8. Gen2Cudas

    Gen2Cudas Well-Known Member

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    I am afraid this did not help as hoped. My symptoms remain. I put it in about 8 inches from the carb, for what it's worth. Worth a shot though; next, think I'll try an electric pump inline.....
    .....though I did think I'd stick a primer bulb n hose under my seat to pull out n squeeze, just to see the expressions on my passenger's faces!

    No telling what they'd think was going on under that seat if I wore a leering grin as I pumped!
     
  9. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    The thing is, there's already TWO check valves in the (mechanical) pump
     
  10. 65Val

    65Val Average Length Member

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    So, why not put this anti-drainback valve right at the fuel tank nipple at the back of the car...that way it'll keep fuel in the entire line/pump/filter system.

    Just my thoughts....
     
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    • mbaird

      mbaird mbaird

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      Damn.... I have been trying to fing the part# for one of those for a while...
      I need another for my 6-pack 70 Charger and another to install on my 68 fastback.

      You sir are a wealth of info !
       
    • teringer

      teringer Well-Known Member

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      we use the 1/2 " check valves on our fire trucks placed about 24" from the fuel tank most of the tanks are 20 plus feet from the engines. and they supply a 525 hp engine with no electrical pump help.
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      Careful, as those are the "opposite" of the 6pack originals. The original 6 pack stuff had the orifice port on the bottom as they had a standpipe inside going to the top. These must have the 1/4" port at the top of the filter.
       
    • Daves69

      Daves69 Well-Known Member

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      So I'm thinking the mechanical fuel pump exit check valve is leaking (not sealing) and draining the fuel line back to tank? Adding a remote check sort of "band-aids" the faulty pump, correct?
       
    • teringer

      teringer Well-Known Member

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      I agree just switch fuel pump first.
       
    • replicaracer43

      replicaracer43 Grumpy Old Man

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      Instead of basic diagnostics, yes this is a Band-Aid. I am still waiting for someone to explain how the fuel could "drain" up hill by the needle and seat. (which is above fuel level) Answer.....it doesn't. It evaporates out of the bowls.....Especially this new crap they call gasoline.
       
    • d55dave

      d55dave Well-Known Member

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      This is absolutely 100% correct. It is kind of like claiming that your kitchen sink is leaking, draining back out the faucet that the water came in through, and putting a check valve in the faucet to prevent it from happening......the fuel evaporates, period. New fuels, and some carburetor designs (carter types) are more prone to this. The solution is to crank the engine on the starter for 4 or 5 seconds if the car has been sitting for while. This allows the mechanical pump to prime the carburetor float bowl, then pump the accelerator a few times to prime the engine, and then start it.
       
    • H20loo

      H20loo Well-Known Member

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      I have these on my boats and they are on the line between the tank and mechanical fuel pump. Not sure of there purpose but I thought it was a safety thing LOL.
      They flow prettygood- more per hour than I can afford!!
       
    • plumkrazee70

      plumkrazee70 Well-Known Member

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      I read through this thread and am not sure if the OP is talking about the same symptoms as evaporation from the carb.

      My thought was the fuel was draining back from the carb to the pump (no fuel visible in the fuel filter) after about 4 days. Crank crank crank, until the fuel filter fills and fire and run...

      This is the issue I am having, and have wondered if there is a check valve in my pump that is bad?
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      I think some of this is related to the late model evaporative tank system IE the "carbon can" some of it may be "modern fuel" that is alcohol and some might be leaky pump check valves, and some of it might be either improperly installed or modified system parts (over the many years) or things plugged allowing vent problems.

      Before I went to EFI the best things I did on my car was simply abandon mechanical pumps, went to a rear electric pump, a carb insulator, and the forementioned Wix style return port filter. They do work.

      This too is a band aid of sorts.
       
    • ntsqd

      ntsqd Well-Known Member

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      And fwiw Summit has them if yer so inclined to try the check valve.
      Some links:
      -6AN

      1/4NPT
      No, neither is $9, but you don't have to feed evilbay either.

      Rear mounted pump with 67's filter or a by-passing FPR would be my first choice.
       
    • Str8up

      Str8up Well-Known Member

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      R you sure it is draining back to the tank and not into the carb. easy way to tell is to mount a clear filter inline just before carb, make sure it is mounted higher than the carb inlet and tilted down slightly towards carb. if it drains. it is going in the carb. often the inlet fitting (with the needle and seat) gets over tighten and holds the float slightly open.
      there is no reason for the fuel to drain back from carb if hoses are tight with no leaks and fuel pump is good. normally when I disconnect the line at the carb it is still pressurized.
      hope that helps
       
    • RedFish

      RedFish Well-Known Member

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      This thread was started on August 4th ( year irrelevant ). Just pointing out that the disappearing "cornahol" fuel issues are a lot like violent crime. Much more common during summer months.
       
    • toolmanmike

      toolmanmike Moderator Staff Member FABO Gold Member

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      I hope it works for you. I still think the majority of the problems come from evaporation and not drain back.
       
    • GaryS

      GaryS Well-Known Member

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      Feel free to correct my thoughts, but since this happens to all my carbureted vehicles, I’ve been trying to analyze what happens, and have some questions to consider.

      After a hot shutdown, heated Ethanol-tainted fuel boils over and the engine floods. This happens to my cars every time when the weather is warm. If it sits for more than a few minutes, and unless it sits for at least a half-hour, I have to floor the pedal to re-start.

      I don’t see a way for the fuel in the bowl to drain back towards the pump, but when the engine and fuel cool, the previously expanded fuel in the bowl drops enough to open the needle valve, which immediately allows fuel in the line to vent while sitting.

      Now, if the needle valve remained closed and there was no opening for the vapor to vent, would the fuel in the line and fuel pump continue to evaporate? If not, there should be enough fuel in the line between the pump and the carb to quickly prime the carb. Not an instant start, but much faster than having to crank for 10-15 seconds, which is what mine average.

      My ’73 D100 sometimes sits for extended periods and though there are no visible signs of leakage I have seen ¼ tank of fuel evaporate over a couple of months, so if I keep the tank full, Ethanol evaporation is a major issue. If I keep the tank only half-full, evaporation loss is noticeably less. Makes you question how much fuel is actually being saved by adding that crap to good gasoline, and if evaporation is causing more pollution than predicted cleaner combustion is actually saving?
       
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