1956 Oliver 5.5 hp won’t start

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  • October 5, 2016 at 11:51 am #45245
    jasonh
    Participant

      I have used the material sold by Ollie for diaphragms. I bought mine through McMasters. The problem is it is not fiber reinforced so it can stretch. Not sure if Ollie’s material is or not. Fuel makes it swell. I have found it does not work well for pumps where diaphragm is also check valves. Seems to be ok for pumps where diaphragm is just a diaphragm and chamber is on larger side.

      October 5, 2016 at 12:34 pm #45246
      Buccaneer
      Participant

        US Member

        I tore the fuel pump apart last evening.
        It only has 15 minutes of run time on
        it at max, using non-alcohol gas.
        I didn’t see any tears in it, but it
        may be slightly stretched / swelled
        in the dome area.
        This material is very thin, (.015, I think)
        and is not fiber re-enforced, but I’m not sure
        a stiffer fiber re-enforced diaphragm would
        work in a non mechanical operated fuel pump??
        The outside of my diaphragm looks a little butchered
        on one side. I cut it a little oversize, then tried to trim
        it (when bolted together) with an exacto knife….
        did not work, lol.
        Have a B&S style fuel pump on order, so will try that.
        The same one worked good on my 5-1/2 hp Fisherman.

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        Prepare to be boarded!

        October 6, 2016 at 10:44 pm #45331
        Buccaneer
        Participant

          US Member

          Yesterday I lapped the two halves of the original fuel pump shown in the photo,
          as it had some rough machine marks and was slightly warped.
          Tested the pump on the Oliver and it made no difference.
          Today the new B&S style pump came.
          I installed it and it started right up. Runs good at mid to fast
          speed with fuel tank at normal height as it would be in the boat.
          At low speed it coughs (starving for fuel) The impulse line on my
          new pump is clear line, and I could actually see flame in the line
          when it coughed!! Once is starts coughing it will die unless
          sped back up. Sometimes it will start back up at "Start" range,
          other times it needs a little choke.

          I have the low speed needle as "rich" as it will go and it still coughs.
          When I had the gravity feed tank on I don’t think it was coughing,
          and the high and low speed adjustments were in normal range.
          With the original fuel pump at times it would pump enough gas
          to keep the engine running, but never at mid to low range.

          Are these symptoms suggesting that I don’t have enough
          crankcase suction at low speeds to supply sufficient fuel,
          and hence, a scored piston or other malady?
          It does have lower compression than I’d like to see, but
          both cylinders are within 3 psi of each other.

          Is it time to tear down the power head for inspection?

          Thanks for your wisdom!

          Prepare to be boarded!

          October 7, 2016 at 9:56 pm #45399
          jerry-ahrens
          Participant

            US MEMBER PAY BY CHECK

            Have you tried to squeeze the primer bulb when the engine is coughing and wants to die out? That would tell you if the fuel pump is bad.

            October 7, 2016 at 11:56 pm #45407
            Buccaneer
            Participant

              US Member

              Jerry, I tried squeezing the bulb when I had the original fuel pump on,
              and it did keep it running. I doubt if my new B&S style fuel pump is bad
              too, so my thoughts were that the engine is low on crankcase pressure / suction
              to operate the pump sufficiently at idle. Is this possible?
              It ran pretty decent with the gravity fed tank hooked up. Strange!

              Prepare to be boarded!

              October 8, 2016 at 3:55 am #45422
              Mumbles
              Participant

                Backfiring into the crankcase is usually a sign of scored cylinders, pistons and rings. The fire is getting past the pistons and igniting the fuel charge in the crankcase. It might be time to do some surgery on her.

                October 8, 2016 at 9:53 am #45427
                jerry-ahrens
                Participant

                  US MEMBER PAY BY CHECK

                  You may have stuck rings too. I don’t remember if that motor has removable intake port inspection covers or not. If it does, you could have a look and see if the rings are indeed stuck. Another quick test would be to remove the spark plugs, then turn the flywheel to bring the piston to TDC. When the piston begins it’s travel back toward the carb, hold your thumb over the spark plug hole. While continuing to slowly turn the flywheel, pull your thumb away quickly…. you should feel a strong suction if the cylinder is healthy. If not, as Mumbles has already pointed out, you may have scored cylinders, stuck rings, etc.
                  Another trick I like to use…. get a clean Windex bottle, and mix some oil and gas up. When the motor begins coughing and running lean, try misting the carburetor inlet with some fuel. Not too much, just a light mist.. if you time it right, you may be able to idle it down. If this fixes the problem, then your carburetor is the culprit.
                  Leaky crankcase halves may be another possibility.

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