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PostPosted: Tue Oct 04, 2022 11:08 am 
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Interesting. I'm accustomed to the output fitting being the 5/16" invert-flare you had in mind. Looks like you've got an NPT (pipe thread) output fitting there. Reminds me of the earliest Slant-6 fuel pumps, the bolt-together Carter items which did have an NPT outlet, with a brass NPT male to IV-flare female fitting in.

In any event, you can sidestep most or all of this quandary by doing the fuel line mod, substituting an appropriate pipe thread-to-hose-barb fitting at the fuel pump end.

Those force figures sound much more appropriate, BTW.

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PostPosted: Tue Oct 04, 2022 7:36 pm 
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Is it possible you were covering up the output hole when you were testing the new pump? This would significantly raise the force required as you’d be compressing air in a small volume.


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PostPosted: Tue Oct 04, 2022 7:51 pm 
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Pierre wrote:
Is it possible you were covering up the output hole when you were testing the new pump? This would significantly raise the force required as you’d be compressing air in a small volume.


Definitely not. Pump was uninstalled, with nothing covering inlet or outlet.

Still puzzled as to the failure mode, but moving on to the NOS AC pump and getting the van running for the first time in half a year. (It’s my only motor vehicle.)

))Sonic((

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PostPosted: Wed Oct 05, 2022 4:03 pm 
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Pierre wrote:
Is it possible you were covering up the output hole when you were testing the new pump? This would significantly raise the force required as you’d be compressing air in a small volume.


No, it wouldn't/no you're not. When you operate the pump lever, you are compressing a spring. The spring is what would compress the air if the outlet port were blocked off.

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PostPosted: Wed Oct 05, 2022 8:40 pm 
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I thought the spring was to return the lever to its original resting position and the diaphragm created a vacuum in the input tube and pressure on the output through check valves in each.

Never mind me then. It’s been a few decades since I touched a non-electric pump.


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PostPosted: Wed Oct 05, 2022 11:35 pm 
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No, no, you're right, pulling the diaphragm is what creates suction at the inlet port. That happens during the intake stroke of the pump, which is the one that happens when you operate the lever against spring tension. Once you're no longer pushing on the lever, that spring tension pushes the diaphragm, which pressurises the fuel inside the pump and opens the outlet/closes the inlet valve and sends the fuel on its way to the carburetor. This spring is about 1" diameter, and it's coiled round the stem of the diaphragm. It can't clearly be seen from outside the pump. There's also about a 3/8" diameter coil spring, a couple inches long, reaching in a curved path from the pump arm to an anchor point on the pump body. That's to keep the pump arm in even, constant contact with the camshaft so there won't be fuel pump knock.

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PostPosted: Thu Oct 06, 2022 5:15 pm 
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Ah! Ok. So he would have to have been blocking the intake port to cause excessive lever pressure. I was thinking the levers on the other side of the diaphragm.

There always electric pump replacements if push comes to have that mount in the same fashion as the stock mechanicals. A low powered one for a stock carb could probably be run on stock electrical.


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PostPosted: Thu Oct 06, 2022 6:22 pm 
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Electric fuel pumps and carbureted engines are a bad marriage. See here.

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