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Why not to forget that you have gravity feed of gas into your engine.

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  • Why not to forget that you have gravity feed of gas into your engine.

    My previous post, located "below" this one, described a fuel problem. This post describes why I had to drain and replace my engine oil. In trouble-shooting my "lack of fuel" problem, I set up a siphon from a one-gallon plastic gas container on the roof of my 57 President Classic into the inlet to my "not OEM" 4-Jet carburetor. The car started immediately, and ran fine. I stopped the engine, went to do something else, and after about an hour, came back to start the car. You guessed it, the siphoned gravity-fed gas drained through the carburetor and filled the cylinders with gas. The engine "locked" due to the rule that "liquid is not very compressible'. The situation was eventually corrected when all the fuel drained into the crankcase. Deciding that oil diluted by about a quart of gasoline was not very good for lubrication, I drained the oil and replaced it with stuff I bought at Wal-Mart. One good thing, I guess, is 1. that the 10% ethanol gas cleaned the spark plugs and, 2. I discovered a cheap oil containing zinc. Also learned something in an article I found on the "Corvette Forum".
    sigpic
    Jack, in Montana

  • #2
    I had a bad fuel pump on a road trip and had to get to the next service station. Fortunately I had a 300 pound passenger who sat on the front fender and the car started! Gravity feed helped get us to the service station, but he had to stay seated on the fender for the car to run
    Dave Warren (Perry Mason by day, Perry Como by night)

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    • #3
      Originally posted by jnfweber View Post
      You guessed it, the siphoned gravity-fed gas drained through the carburetor and filled the cylinders with gas.
      Just out of curiosity, shouldn't the float/needle and seat be able to stop the flow of fuel when the chamber is full? Wouldn't a fuel pump put more pressure to the carb. than gravity? Might the float be a little out of adjustment or the needle and seat not sealing properly?

      Or maybe, was the car jacked-up in the front making the carb not level?

      regards,
      Jay
      Last edited by IMJ; 05-14-2014, 06:31 PM.

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      • #4
        I've heard it is possible to bend a connecting Rod just using the started motor with hydrostatic lock. Probably rare. Hope your starter was not super efficient.

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        • #5
          Ever disconnected the fuel tank-to-pump line on your Avanti & turn your back? That tank empties quite fast when you are looking for a golf tee to plug the line.

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          • #6
            Originally posted by Deaf Mute View Post
            Ever disconnected the fuel tank-to-pump line on your Avanti & turn your back? That tank empties quite fast when you are looking for a golf tee to plug the line.
            Very true. But if I read the scenario correctly, the fuel from the gas can on the roof was connected directly to the carbs. inlet. So my thoughts were that if the carb. was level the float should have been able to close the needle/seat. Inquiring minds need to know.

            regards,
            Jay
            Last edited by IMJ; 05-15-2014, 06:11 AM.

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            • #7
              Originally posted by IMJ View Post
              Very true. But if I read the scenario correctly, the fuel from the gas can on the roof was connected directly to the carbs. inlet. So my thoughts were that if the carb. was level the float should have been able to close the needle/seat. Inquiring minds need to know.

              regards,
              Jay
              I had expected the needle/seat to prevent over-filling of the carburetor, as I had tried this trick on an Avanti with a blocked/rotted gas hose just below the fuel tank. The garage floor is not quite level, and without blocks behind the wheels, the car would roll backwards into the driveway, across the road, and down into the canyon. Honest--there is a canyon across the road. Everything worked out, the car runs well (I had adjusted the floats without replacing anything this winter.) I had repaired the Rochester 4-Jet bowl with J-B Weld and sealed the lid with Permatex Ultra Black, and had let the car set for 3 months. So far, no leaking from the "repaired" carburetor. I had purchased some Permatex A-2 just in case my leak repair (silicone sealer) failed. Better to be "lucky" than smart. http://forum.studebakerdriversclub.c...light=jnfweber

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              Last edited by jnfweber; 05-15-2014, 08:49 AM.
              sigpic
              Jack, in Montana

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              • #8
                And,when you're looking or a gas leak-don't jack the rear of the car up and then leave for lunch. I came back to the shop and had a 10 foot diameter gas puddle.
                Oglesby,Il.

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                • #9
                  If it was a full gallon of gas, wouldn't there be close to 8 lbs of pressure with the container
                  on the roof of the car? Just making a guess.

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                  • #10
                    Originally posted by Son O Lark View Post
                    If it was a full gallon of gas, wouldn't there be close to 8 lbs of pressure with the container
                    on the roof of the car? Just making a guess.
                    "The situation was eventually corrected when all the fuel drained into the crankcase. Deciding that oil diluted by about a quart of gasoline was not very good for lubrication, I drained the oil and replaced it with stuff I bought at Wal-Mart."

                    I originally thought the same thing but then I remembered a quart or 1/4 gallon. (2 lbs)
                    I thought maybe the front of the car was on jack-stands which would angle the carb. back and flood it.

                    regards,
                    Jay

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                    • #11
                      Originally posted by IMJ View Post
                      "The situation was eventually corrected when all the fuel drained into the crankcase. Deciding that oil diluted by about a quart of gasoline was not very good for lubrication, I drained the oil and replaced it with stuff I bought at Wal-Mart."

                      I originally thought the same thing but then I remembered a quart or 1/4 gallon. (2 lbs)
                      I thought maybe the front of the car was on jack-stands which would angle the carb. back and flood it.

                      regards,
                      Jay
                      There was about one-half gallon of gas in the tank when I started, and about a quarter gallon when I discovered the problem. I don't know how many pounds that would be, but I am not very good in fluid dynamics. 8 pounds of pressure, or foot pounds, or ergs, I have no idea. I should change my signature to "Dumb but lucky." At least there was no gas spilled on the engine or garage floor, or KA-BOOM!
                      sigpic
                      Jack, in Montana

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                      • #12
                        I did this one a car with a bad needle and seat, we pulled the plugs and cranked it, my brother sitting next to fender and underestimated how far the would shoot, and all went right into his eyes.

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                        • #13
                          Originally posted by GThawkwind View Post
                          I did this one a car with a bad needle and seat, we pulled the plugs and cranked it, my brother sitting next to fender and underestimated how far the would shoot, and all went right into his eyes.

                          Ouch ! I got my eyes, ears, and nose doused with gasoline when I detached a blocked rotten hose from the bottom of my Avanti gas tank. Quick run into the house to wash with water from kitchen sink. Ears were the worst, had to use kitchen sink spray to clear them out. I bought this car in Tulsa in 1989 and sold it in Montana in 2013. It showed up several days later at a local golf course. It is in storage and current owner is trying to sell it for twice what he paid for it. Photo was the one I took at the golf course.


                          sigpic
                          Jack, in Montana

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                          • #14
                            Oh thank goodness! I though I was going to have to see another "garage fire engulfs classic car" photo!

                            I use these for safety...only $6.00



                            Better than this...Yikes!

                            Last edited by SweetSixtyn; 05-21-2014, 07:54 AM.

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                            • #15
                              Heh. Timely topic. Yesterday, I started up my old Dixon ZTR mower to move it over by the shop so I could replace the cones and wheel cups in its fabulous friction drive mechanism. Started kind of reluctantly, and blew out huge clouds of blue smoke, but I made it from the barn to the yard by the shop, where it quit from running out of gas. I got the parts changed, and even popped the grease seals out of the 6 bearings involved and hand-packed a little more grease into them. Figured I'd check the oil while I was at it. Pulled the dipstick, and uh-oh! Waaay over-full. The fuel tank had drained into the crankcase over the winter. So I drained the much-diluted oil, filled it with fresh, and filled the fuel tank. It started right up, and I got a bunch of mowing down. Steering levers still need to be set up a bit, but it still does what it has to do. Needless to say, there is a small placard on the engine housing, advising that the fuel valve should be shut off when unit is not in use. Guess I will be doing that from now on.

                              Oh, and pressure? A column of water 30 feet high has a pressure of of about 14.7 pounds per square inch = atmospheric pressure at sea level. A column of water 3 feet high would have about 1.5 psi. Gasoline, being about 8/10 the density of water, would be 1.2 psi. Assuming that a gas can on the roof would be a full 3 feet above the fuel inlet on the carb.

                              It's not necessarily the pressure that does it. Certainly not in the case of my lawnmower. Could be a little dirt in the needle and seat; or it just could be that gas in the carb bowl evaporated, and the float dropped by gravity, and fuel trickled in, as per design, but the float did not rise enough to close off the flow again, because, no vibration from running engine. One tiny little bind on the pivot pin, or needle and seat, and the relatively tiny force of the float could be neutralized. Normally, vibration of a running engine is enough to overcome static friction between the metal parts that make up the float valve mechanism. Remember that gasoline is NOT a lubricant.
                              Gord Richmond, within Weasel range of the Alberta Badlands

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