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Holley 2300 accelerator pump sticking
https://slantsix.org/forum/viewtopic.php?t=68469		 Page 1 of 1
Author:  Reed [ Tue Dec 23, 2025 3:35 pm ]
Post subject:  Holley 2300 accelerator pump sticking
I am running a Holley 2300 Economaster on the otherwise stock 225 in my 76 D100. I discovered yesterday that the accelerator pump arm locks up solid in the compressed position. I can disassemble the pump and see there is nothing in the diaphragm, the spring is on the right side of the diaphragm, and there doesn't appear to be anything wrong with the castings. Upon reassembly I can get one good compression and return of the accelerator pump but on pump #2 the lever locks up solid in the compressed position.

What the heck? :?: :? :?:

I am not really a Holley guy and don't know much about their intricacies. :|
Author:  Killer6 [ Sun Dec 28, 2025 1:46 pm ]
Post subject:  Re: Holley 2300 accelerator pump sticking
Quote:
I am running a Holley 2300 Economaster on the otherwise stock 225 in my 76 D100. I discovered yesterday that the accelerator pump arm locks up solid in the compressed position. I can disassemble the pump and see there is nothing in the diaphragm, the spring is on the right side of the diaphragm, and there doesn't appear to be anything wrong with the castings. Upon reassembly I can get one good compression and return of the accelerator pump but on pump #2 the lever locks up solid in the compressed position.

What the heck? :?: :? :?:

I am not really a Holley guy and don't know much about their intricacies. :|
If it's not a mechanical binding/interference thing, is it possible the bowl check valve is installed on the wrong side(EDIT: if that's a check-ball bowl, make sure it isn't getting stuck.)? If I'm understanding what You're stating correctly, the diaphragm stays "up" in the cover, not returning after it is depressed.......correct or no?
Author:  Reed [ Mon Dec 29, 2025 12:35 am ]
Post subject:  Re: Holley 2300 accelerator pump sticking
Yes. The diaphragm compresses once but stays compressed lie there was a vacuum holding it shut. I am pretty sure it is a 30cc diaphragm and spring, and the pump lever moves freely if I loosen the pump cover. Also, the diaphragm releases and pumps freely if I loosen the diaphragm cover slightly. I need to pull the carb and disassemble it. It might be some weird mechanical linkage bind-up. In the meantime, my 500 CFM Carter AFB will go back on so I can at least move the truck around.
Author:  Reed [ Wed Jan 07, 2026 9:25 pm ]
Post subject:  Re: Holley 2300 accelerator pump sticking
POST-OP DEBRIEF:

I disassembled the accelerator pump. The pump came free when I loosened the last pump cover bolt. Nothing was obviously wrong. I carefully reassembled it and now it works fine with no sticking. :? :? :?:

My only thought is that the holes for the diaphragm were oversized enough to allow the metal disc on the pump diaphragm to get offset enough to jam up when the pump was operated.

My conclusions:
(1) when using a carb with a Holley style accelerator pump, be careful when assembling the accelerator pump and make sure it moves freely after assembly;
(2) use a carb with a shaft-and-plunger style accelerator pump. 8)
Author:  Reed [ Sat Jan 10, 2026 4:28 pm ]
Post subject:  Re: Holley 2300 accelerator pump sticking
Well, the problem was not solved. Accelerator pump is still jamming. It is coming off and being replaced with a 500 CFM Carter AFB until I have time to tear the Holley 2300 down further.
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