fuel pump question on 1966 CD-23

[SCOTT MEYER]

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).

[frankr]

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.

[SCOTT MEYER]

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

[SCOTT MEYER]

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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