fuel pump question on 1966 CD-23

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  • June 1, 2015 at 3:50 am #1651
    SCOTT MEYER
    Participant

      US Member - 2 Years

      This motor has the original style pump (not the later square replacement).
      Would running the carb dry with the fuel hose disconnected cause any undue stress on the pump diaphragm? I ask because after a tune up and successful barrel test I ran the carb dry and delivered the motor to the owner only to have it exhibit symptoms exactly like a pinhole in the diaphragm. I couldn’t get it to idle worth a crap but it would run great at higher throttle. The plugs looked wet when I pulled them. I had it running like a Swiss clock 😥 and I’m trying figure out what happened between then and when I delivered the motor (a 50 mile ride in the trunk of my car).

      June 1, 2015 at 8:49 am #17336
      frankr
      Participant

        US Member

        Millions of motors get run dry without damaging the fuel pump. But that doesn’t mean that there might not be a coincidence happing here. Stuff happens. Remove the pump from the motor (hoses attached) and squeeze the primer bulb. If gas squirts out the back, diaphragm is holed.

        June 1, 2015 at 4:52 pm #17355
        SCOTT MEYER
        Participant

          US Member - 2 Years
          quote FrankR:

          Remove the pump from the motor (hoses attached) and squeeze the primer bulb. If gas squirts out the back, diaphragm is holed.

          Thanks a bunch, Frank. That was gonna be my next question. I’ll try that when I get home from work today.
          The owner bought it 3 years ago from a dealer on a consignment I think and doesn’t have any maintenance history on this one.
          By coincidence I see on another posting below that these pumps are repairable, so that may be in my future.

          Thanks again, your input is valued and appreciated.

          scotty

          June 2, 2015 at 2:51 am #17395
          SCOTT MEYER
          Participant

            US Member - 2 Years

            Just an update – I checked the fuel pump for leaks and it checked out good.
            I then took out the low speed needle and noticed some red fibrous looking stuff on the end of the needle. I first thought it might be old packing that I missed while cleaning.
            Then on closer inspection I realized it was threads from my cheap red Harbor Freight shop towel that I had probably stuffed it into the hole to wipe the threads clean and snagged on a burr. I removed the carb and disassembled for a thorough inspection. Reassembled and back into the test barrel. Ran good and idled down fine once I found the sweet spot on the needle. Lesson learned.
            This one likes the needle somewhere between 1/2 to 3/4 turn out from seated and is very sensitive. I’m gonna keep it a couple more days to run it and make sure it’s happy before delivering it to the owner again.

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