air is present in see thru fuel filter

Fuel and Air Systems

  1. Ray70Chrg

    Ray70Chrg Well-Known Member

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    This is 1st time I've ever used a clear plastic filter and I have used it for a couple of years now. I got it so I can see how much crap has accumulated. From the beginning I noticed their was air in the filter but the engine seemed to run ok. Is it normal to observe this condition or is this a problem? Thanks
     
  2. 70chall440

    70chall440 FBBO Gold Member FBBO Gold Member

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    Yes, every one I have ever used has shown at least some amount of air.
     
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    • Jerry Hall

      Jerry Hall FBBO Gold Member FBBO Gold Member

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      As far as I know this is common. I seldom use the clear filters, but have seen it before.
       
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      • Cranky

        Cranky Banned Staff Member FBBO Gold Member

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        Air in the fuel system isn't like air in the brake system. So long as the carb bowls are full, the engine doesn't care.
         
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        • moes

          moes Well-Known Member

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          just my 2 cents worth...I always thought the space you see in a clear filter when it is 3/4 full was filled with gas vapors and that way you always have a full filter. That way you still have a continues flow of gas while the car is running.
           
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          • Kern Dog

            Kern Dog FBBO Gold Member FBBO Gold Member

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            It is normal but defies logic to me.
            It seems to me that the filter should be full of gas since the system is pressurized.
             
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            • Ray70Chrg

              Ray70Chrg Well-Known Member

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              Thanks to all, it's nice to find out I don't have another mystery to solve. It's like getting a day off for free.
               
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              • MoparLeo

                MoparLeo NRA PATRON LEVEL LIFE MEMBER FBBO Gold Member

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                OK as long as you are not seeing bubbles forming while it runs.
                 
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                • BeepBeepRR

                  BeepBeepRR FBBO Gold Member FBBO Gold Member

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                  I would advise against using one of those MrGasket type clear filters. Its an accident waiting to happen. Glass tube sandwiched between two ends.... Glass breaks and you have a potential for a fireball.

                  81XHXD9edWS._AC_SL1500_.jpg
                   
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                  • RJRENTON

                    RJRENTON FBBO Gold Member FBBO Gold Member

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                    IMO....
                    The void space you see is actually fuel vapor not air. In the OEM fuel system used on the Hemi and Six Barrel engines, use a "fuel vapor seperator" to insure that the carbs receive only liquid.
                    BOB RENTON
                     
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                    • Cornpatch MO

                      Cornpatch MO Well-Known Member

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                      If the fuel filter was mounted straight up and down, I don't think you could have that air gap. Mounted at an angle , I think you would have air trapped in the corner. ........................MO
                       
                    • Kern Dog

                      Kern Dog FBBO Gold Member FBBO Gold Member

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                      I've used these for years on several cars with zero problems.
                       
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                      • BeepBeepRR

                        BeepBeepRR FBBO Gold Member FBBO Gold Member

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                        I said potential fireball... I have seen one break but that's one too many.
                         
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                        • Dibbons

                          Dibbons Well-Known Member

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                          On my '70's bracket racer, I had two see-through plastic filters on my Holley double pumper (dual feed-two float bowels) and noticed them only half-full.

                          At the drag strip, I filled my aluminum fuel can (it was not insulated like the new ones sold today) with dry ice and the vapor/air was eliminated in the fuel filters. The dry ice was expensive and a pain to purchase, so I went to using plain ice after that time. With the regular ice, the vapor in the filters was also eliminated.

                          When cruising Main St. on Friday nights in the bracket racer without any ice in the cool can, I don't remember the status of the fuel filters while driving on the street after have had used ice a few days previous to that.

                          cool can.jpeg 65 Valiant  moter head on shot.jpg cool can 2.jpeg
                           
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                          • mopar jack

                            mopar jack Well-Known Member

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                            A carbed fuel system pressure is probably around 6 psi but the reid vapor pressure of the fuel is 7 psi or greater depending on winter/summer grade and temperature.
                             
                          • Cranky

                            Cranky Banned Staff Member FBBO Gold Member

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                            It's pressurized between the pump and the bowls....

                            What caused it to break? Was it laying against something? I too have used them on cars that were having issues with trash but always made sure they were not against anything and didn't have any stress on them from the fuel line.
                             
                          • BeepBeepRR

                            BeepBeepRR FBBO Gold Member FBBO Gold Member

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                            It was in my neighbors silverado. I think it was tinking on the intake for a while and just broke. I replaced it with one of the metal can style ones and no problems there..
                             
                          • Kern Dog

                            Kern Dog FBBO Gold Member FBBO Gold Member

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                            Those don't allow you to see when fuel is in the line. To me, that makes them worthless.
                             
                          • BeepBeepRR

                            BeepBeepRR FBBO Gold Member FBBO Gold Member

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                            Well, if you are not getting gas you are not getting gas. Doesn't take a degree in rocket science to figure that out. You can choose those clearish plastic ones too. Personal preference I use something that is meant to be durable. Glass is one thunk away from pumping fuel all over the place.. Your choice, no big deal.
                             
                          • joemish

                            joemish Well-Known Member

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                            It is very normal as the filter is NEVER filled solid with liquid.
                             
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