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Fuel System Basics and Filtering Options

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  • Fuel System Basics and Filtering Options

    Fuel System Basics and Filtering Options

    The stock Model A fuel filtering consists of a stand up pencil type filter screen on top of the tank shutoff valve which sits inside the tank, (these pencil filters were not used when the car was built) a cast iron or glass sediment bowl and an inlet screen at the carburetor. The late 31 indented fire wall models have the shut off valve under the hood and uses a side bowl type carburetor to filter it. A badly rusted tank should be removed cut open and cleaned out, Brent Terry is one of the few that do it this way, here is his site link
    Others have sealed their tanks with mixed results as today's modern fuels tends to attack certain types of available coatings. I have used evapo-rust with good results for dissolving rust, with that being said another good alternative is to just find a good used tank. Timothy Kelly came up with this dirty leg trick that many have used to trap the garbage, but this could be an ongoing process if the main cause is not.addressed properly . Here is the Ford Garage site link to Tim's setup,
    A tight / hard to turn or not sealing shut off valve can be caused by debris being caught up in it.These can either be rebuilt or replaced, but always install a new pencil screen in the valve as originally they were not used. These pencil filter are your first line of defense to prevent particles from going down stream. If your taking the rebuild route many folks have had success lapping the parts with toothpaste, but inspect for scoring or galling on the ball. There is an optional fuel filter that can be installed in the glass style sediment bulb. These glass bulb filters do not restrict the flow to the carburetor as some of the in lines do. The NAPA number is 3034 and the WIX number is 33039 or you can cross-reference these to your favorite brand. The suppliers such as Bert's Model A now also sell this style filter FYI. These filters are suspended by the glass bowl itself, it sits in the depression at the top of the glass. Therefore no spring or such is needed below the filter to hold it up against the incoming fuel. . The main fuel feed into the sediment bowl is down through the center where the original screen has a hole. Any junk will flow in through there and get trapped in the filter before it goes out through the mesh screen. Leaving the original mesh screen in place is a good idea as this will act as a double back up per say. Install the items in this order,
    Sit the filter into the bowl first having it rest on the depression
    Install a new cork bowl gasket up into the sediment upper housing, and place the screen in the depression of the glass bowl above the filter. (below the gasket) Always try to use a cork gasket instead of neoprene as the cork tends to hold up better with the crap gas we have now a days.
    Please refrain from using the inline type filters where you cut the feed line between the sediment bowl and the carb and use rubber hoses. These type of filters have been known to impede the natural gravity flow of the fuel and they can also be a fire hazard since some of these are plastic, plus having the rubber lines near the hot exhaust manifold is also a bad idea.
    Lastly there is a screen at the fuel inlet of the carburetor which is sometimes forgotten about

    pencil filter:::::carburetor inlet screen filter:: WIX 33039, NAPA 3034 sediment filter

    3 ~ Tudor's
    Henry Ford said
    "It's all nuts and bolts"

    Mitch's Auto Service ctr

  • #2
    More fuel filtering info

    If you install a new needle and seat and the carb still leaks, make sure you aren't sending rust and junk down the line.
    The pencil filter in the top of the tank valve is an important first step.
    If you have a cast iron sediment bulb,make sure it's spotless clean inside, or you may be sending junk down the line.
    I forgot to show the lock washer in picture 4.
    Don't overlook the final filter in the carb, as I've see rust collected there also.

    Here is a link to the main thread for addntl info


  • #3
    Here are 3 pictures showing the 3 filters every Model A should have. The tank filter is an aftermarket item, but very important to keep junk from messing up the tank valve and carb. The second picture shows the cast iron sediment bulb, but many have the clear glass instead. I took these pictures of the cut away Model A that used to be at the Gilmore Model A museum in Hickory Corners, Michigan.


    • #4
      Fuel LIne Install

      If the ferrule is seated to far onto the steel feed line this will restrict the fuel flow to the carburetor. Here is one sure fire way to get it right as the approx distance needs to be about a 1/16th.

      To set the ferrules for the gas line at the proper distance from the ends of the tubing, remove the filter screen on the carburetor. Obtain a 1/2-20 bolt about one inch long. Screw the bolt into the hole where the filter screen was. Put a nut and ferrule on the gas line, insert into the fuel inlet allowing the gas line to touch the bolt. Tighten the nut to seat the ferrule. Remove the gas line and swap ends to repeat the procedure. Using this procedure, the gas line enters the carburetor and the sediment bulb assy at a distance to allow full fuel flow.

      It takes a lot of pressure to squeeze the ferrule and make it snap off the nut. Sometimes I score them a little more so they snap off easier.
      3 ~ Tudor's
      Henry Ford said
      "It's all nuts and bolts"

      Mitch's Auto Service ctr


      • #5
        Here's my set up; the Wix filter/ gasket is available on line for a couple of bucks ( AC fuel bowl ). The glass bowl holds the gasket/ filter in place. I installed a coat hanger type wire connecting the (drip A gas valves.pdf insurance) ball valve handle thru a tiny hole in the fire wall for shut offs at outings.



        • #6
          I ONLY ever use the "pencil" filter, the cast sediment bowl & the filter in the top of the Zenith! NEVER had any problems, even with some rust flakes in the tank!
          I would NEVER re-seal a tank!!!!---Like opening a can of WORMS!!!
          Bill Troublefree


          • #7

            Thank you for this thread.

            I will I’ll purchase some cork gaskets, and scour that fuel bowl.

            Thank You;

            Brian French


            • Mitch
              Mitch commented
              Editing a comment
              Those bowl filters work great

          • #8
            Outstanding Post....thank you


            • #9
              OK, I somehow missed all this the first time around. Excellent thread.
              1 question, 1 comment
              1) plyfor, how did you get the right angle brass fitting to seal in the shutoff valve on the firewall? That thread is machine, not NPT
              2) If you are using a die cast carb (Tilly), set your ferrules by inserting them into a cast Zenith, because to properly seat the ferrule, you need a fair bit of torque, and you don't want to stress the threads in the Tilly, they are soft


              • #10
                Way overdone topic.

                I think it important that it is understood that the original A filters are very effective.

                For example, the fordor I owned had the rust settle into the valve problem. The car would start go a bit then stall. You blow back on the line and you were fine for a while.

                I took the valve off the tank and put a ball valve in place. Put some gas in the tank and shook the car hard. Then rapidly drained through a rag into a container. I repeated till the amount of junk was much much less.

                Then I put a short bit of 1/4 tube into the original valve before I put it back in the tank (this was not an indented firewall car) so the dirt settling could not clog the valve.

                I put everything together being sure the original filters were in good shape. They should not be crushed like in the cut away picture above.

                So now the crap in the tank was being caught by the sediment bowl. Over a period of time driving the amount of rust caught in the sediment bowl dropped off dramatically. Sadly, I decided to sell the car so I could build the cabriolet. I was getting to the point of removing the copper tube in the tank so I could use all the gas in the tank.

                You see the above method is not a band aid. It is the cure for the problem. I got the bad stuff out of the tank and did not have to need the filter screen the rest of the life of the car. I should also mention I monitored the carb bowl (I only use the original carbs). Never did I get anything in the bowl but nice clean gas. So you are really much better off making sure you have good original filters then adding something to the line.


                • Mitch
                  Mitch commented
                  Editing a comment
                  Thanks for your real world information, that's what this site strives for. There are usually many ways to skin a cat, so having many proven options listed available is a good thing.

              • #11
                Sediment Bowl Screen Filter Info:

                When buying my 1930 Coupe in 1958 for $25.00, the very kind former owner and neighbor showed me why to never omit the sediment bowl screen filter ...... he removed the screen filter, placed water on it, and even minute drops of water would not pass through the tiny holes in this screen filter.

                Next he showed me that when water could not pass through the sediment bowl screen filter, water from the gas tank was noticeably encapsulated at the bottom of the glass sediment bowl, with gasoline floating on top whereby accumulated gas tank condensate water could not get to the carburetor.

                I soon realized that this vintage mechanic was really an analytical genius.


                • #12
                  Wanna get rich? Invent a GOOD fiberglass tank that is dead on to an original..
                  Good enough.. Isn't.


                  • plyfor
                    plyfor commented
                    Editing a comment
                    good point; we just pulled a '22 Lincoln rusted gas tank that had a complicated baffle system inside. No way to clean, etc. so our vendor cut out the top (hidden under car rear) removed the baffles, welded back the sheetmetal and $800 later, clean gas!

                • #13
                  Mitch Great bit of information and the pictures and information was a big help thank you


                  • #14

                    Glass Bowl 101:

                    A. After proper glass bowl installation, this glass sediment bowl was designed to have the top of the glass bowl in contact with the bottom of a proper fitting upper glass bowl gasket; either cork or even better as advertised neoprene ...... and most importantly with gaskets as offered "only" by a reputable Model A parts supplier like Bratton's or several others.

                    B. Next the top of this same proper glass bowl gasket has to be in contact with the upper metal; i.e., solid top of glass surface to bottom of soft gasket, and solid top metal to top of soft gasket ............ not much different from millions of soft leak proof gaskets used Worldwide.

                    C. In carefully reviewing a proper Model A glass bowl when held upright, this bowl has an upper-inner recess which is designed to receive the metal filter screen.

                    D. If a new, poorly made screen is too large in diameter to neatly fit in this recess, this screen has to be carefully trimmed to fit down in this glass bowl recess; otherwise, the joining of this joint between the glass sediment bowl and the screen will leak through the openings in the screen.

                    E. A major problem is that some first place the gasket on top of the glass bowl, next place the metal filter screen on top of the gasket, and install this assembly with the screen in contact with the metal surface above, which is also guaranteed to leak.

                    F. After trying to understand these instructions, if one has a glass bowl that still leaks, try getting one of those Teeter-Totter Pain Relief Spinal Back Extenders Contraptions, rotate your body upside down, and try to assembling your glass sediment bowl while resting upside down.

                    Hope this helps.


                    • #15
                      Electric fuel shutoff maintenance

                      You might want to open up (remove the plunger) in your fuel shut off solenoid and clean the insides good with spray carb cleaner. I have to do this a couple of times a year because of the gas, even though I use MMO generously and Stabil or SeaFoam. You want to hear a "solid" click when you turn the key on. If it doesn't fully open you'll get fuel starvation symptoms.
                      Paul in CT


                      • #16
                        Additional fuel filter info!

                        Here is a little more info regarding the Wix 33039 glass bowl filter. The filter sits on the depression as pictured here. This is what holds the filter in place..

                        3 ~ Tudor's
                        Henry Ford said
                        "It's all nuts and bolts"

                        Mitch's Auto Service ctr


                        • #17
                          3 ~ Tudor's
                          Henry Ford said
                          "It's all nuts and bolts"

                          Mitch's Auto Service ctr


                          • #18
                            Nov 2018 Newsletter

                            3 ~ Tudor's
                            Henry Ford said
                            "It's all nuts and bolts"

                            Mitch's Auto Service ctr


                            • #19
                              Tim Kelly’s dirty leg setup:

                              3 ~ Tudor's
                              Henry Ford said
                              "It's all nuts and bolts"

                              Mitch's Auto Service ctr


                              • #20
                                More dirty leg info!

                                Original Thread

                                I finally sorted this all out. It took countless trips to my local Farm'n'Fleet store - LOL! I was sure I had the right fitting each time. But I didn't.
                                First I have a caveat - car is a 1930 Murray Town Sedan. Don't know if tank is original. The glass sediment bowl obviously doesn't look original - that nut on the back of the firewall looks new. I re-used my fuel line that was in the car, 5/16" steel tube, has a seam down the tube, with 3/8" flares on each end.

                                The connection on the bottom of the tank is indeed 1/4" - I used a 1/4" close nipple, 1/4" tee with (2) more 1/4" close nipples and 1/4" valves - all pipe thread. Closing the "dirty" leg valve is a 1/4" pipe thread hex plug. I flattened and shortened the valve handles. They were huge.
                                The area I had issues with was the flares and the size of the tube. The tube is not 1/4" it is 5/16" and I used a 5/16" compression union to shorten the length of the tube. The flares are 3/8" - on the old shutoff valve and on the back side of the sediment bowl at the firewall. Be careful with the sediment bowl, it is pot metal (at least this repo is) and is easy to cross thread. I wish it had been pipe thread so I could put a good brass fitting into it.
                                Hope this helps someone. Definitely a plumbers nightmare.
                                Dan Reynolds


                                • #21
                                  Gas Cap Vent

                                  3 ~ Tudor's
                                  Henry Ford said
                                  "It's all nuts and bolts"

                                  Mitch's Auto Service ctr


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