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PostPosted: Tue Dec 12, 2017 5:43 pm 
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The diaphragm wore out in my stock '63 fuel pump (Carter). Everything with the carburetor (stock) had been working OK up until the pump failed. I rebuilt it with a kit from Then & Now Automotive and reinstalled it. The engine ran at choke, then idled normally for about 15 minutes. Then the RPMs dropped and the engine stuttered. Goosed the accelerator and it smoothed out and ran normally. Then it happened again. Happened twice more, then the carburetor literally overflowed with fuel.

I thought there might be grit or sediment that had been pulled into the carb by the newly-rebuilt pump, possibly clogging it, so I pulled it and rebuilt it (feeling like it was overdue anyway) with a kit from Daytona. Reinstalled the carb and the same thing happened: overflow.

Pulled the carb and inspected the floats: they aren't taking on fuel and the newly-designed Daytona float valve (their replacement for the stock needle & seat design) seems to be seating correctly. Made sure the floats were adjusted to provide correct fuel level in the bowl.

I've never had this problem before. My next step is going to be to check fuel pump pressure. Don't know how it could be that, but I didn't have any problem with the carburetor until I reinstalled the rebuilt fuel pump.

What's the best way to check fuel pump pressure when the car isn't running? Is there a way to check tension on the main spring to gauge the kind of PSI it will output?


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PostPosted: Tue Dec 12, 2017 6:38 pm 
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Disable the ignition by removing the + primary wire from its threaded post on the ignition coil and taping off the end of the wire. Put your pressure gauge securely on the top end of the fuel line (where it normally attaches to the carburetor). Crank the engine and see what the gauge reading builds to; you're looking for 3 to 5 psi.

I think the problem's probably with the inlet needle/seat, but make sure the float hinge pin retainer is in place.

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PostPosted: Thu Dec 14, 2017 2:45 pm 
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Thanks for the tip Dan. Going to have to get a fuel pressure gauge to test.

I'm wondering if the new Daytona float valve needs additional compensating on the float tang to keep the correct fuel level in the bowl. A small leaflet accompanying the carb kit goes into much detail about how their new float valve is far superior to the stock design, yet they say nothing about needing to deviate from spec stock float crown-to-fuel-bowl-surface level because their valve runs fuel in the bowl leaner with a much shorter open.


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PostPosted: Thu Dec 14, 2017 5:37 pm 
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You shouldn't need to change the float adjustment from spec, but you do need to check it at every rebuild, even with an ordinary-type inlet needle/seat. That raises an important question: how did you check and adjust the float level? Carb kits, no matter where you get them, don't come with usable float gauges any more. Now you just get a completely useless strip-of-paper ruler. See here.

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PostPosted: Sat Jan 06, 2018 4:28 pm 
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SlantSixDan wrote:
...That raises an important question: how did you check and adjust the float level? Carb kits, no matter where you get them, don't come with usable float gauges any more. Now you just get a completely useless strip-of-paper ruler. See here.


Yes, checked at every rebuild. And yes, no useable float gauge which has always confounded me. While in the past I have trailer-trash eyeballed it (and probably paid for my lack of preciseness in fuel economy and performance), this time I drew a gauge on paper, measured precisely for 7/32" and glued to a gasket backing cut to size. Still a mickey-mouse job, but better than what I was doing.

I should have gone with my gut and the most obvious problem from the get. Upon testing, the newly-rebuilt fuel pump is reading 10-12 PSI when cranking and while running badly with a dripping carburetor, about the same.

The new pump diaphragm spring is too strong and it's pushing past the new fuel inlet valve, flooding everything. :evil:


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PostPosted: Sat Jan 06, 2018 5:30 pm 
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Gross! They sent you a diaphragm assembly with the wrong spring. I'll be surprised if they don't step up and make it right.

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