I have a 66 chrysler new yorker with a 440 and an original carter afb 4131s. The problem I am having is the napa parts kit accelerator pump is getting seized in the bore. The leather style pump goes into the bore ok and will work properly. Then the next day there is no pump shot. I pull the top off the carb and the pump is stuck in the bore. The leather seems to swell and bind in the bore. I am in question if the supplied pump is too large. I don't have an accurate way of measuring the bore at the bottom of the taper. I measured some various sockets and then dropped them into the bore. I come up with .72" - .73"......when I measure the piston I seem to come up with about .76" around the center of the seal. Can someone help me figure out what size pump I should have, and where the measurements should be taken.
talk to the carb king in Missouri be careful what you say to him. He treats everyone as if they are REAL stupid
A true leather pump will not swell; however it may still stick in the pump cylinder due to the gooey residue left from evaporating modern fuel. Neopreme pumps can certainly swell and stick in the cylinder, due to the presence of ethanol in modern fuel. However, more often than not, the lack of accelerator pump shot with a cold engine is the result in there being no fuel in the fuel bowl due to evaporation. Before blaming the NAPA pump, try testing the accelerator pump. To do so, first start the engine. Now you know there is fuel in the carburetor. Now turn off the engine, remove the air cleaner, manually open the choke butterfly, and while looking in the primary side of the carb; work the throttle to wide open. You should observe 2 small streams of fuel from the pump jet. If yes, the pump is OK; if no, then time to check the entire pump circuit. Jon.
Thanks for help. As I originally stated the pump works good until the next day. No pump shot present at the nozzles but 5psi on the gauge prior to the carb. Carefully removing the carb top gas is even with the slot of the pump well, I find the pump stuck in the bore where the only thing moving is the top of the pump stem collapsing the upper overload spring but not the pump seal itself. The top side of the pump seal at rest/idle is about even with the top of the slot of the well putting the seal in the bottom of the taper (maybe a touch deeper). I can rock the pump in a circular motion and get the pump to somewhat work. I removed the bottom spring wondering if the added resistance was causing me issues but no change. I posted measurements of the well and seal (dry).. I question if the seal is incorrectly sized for the well? What size pump is a well measuring .72"-.73"?
Carter used 5/8, 11/16, and 3/4 inch pumps in the AFB. Since a 3/4 would not fit into 0.72 or 0.73, it probably used an 11/16 inch. Your comment concerning the pump not moving is confusing to me. When the pump is properly adjusted, the articulation spring will not start to collapse until the pump contacts the bottom of the pump well. Even if the pump were partially stuck at the top of the cylindrical portion of the pump well, moving the throttle to wide open should force the pump with the articulation spring completely collapsed to move downward and give a shot of fuel. Jon.
Yes you are correct at somewhere around 2/3 throttle opening the pump will force down and deliver fuel. But next stroke will be stuck at the top again only moving the overload spring. Thus obviously giving no fuel shot when moving the throttle in any normal cruising positions. According to all specs on the kit I have the pump adjusted correctly. I wonder if buying a 11/16" plunger is the answer? My plunger measures about .76" around the seal over the round spring inside the leather.
The original Carter accelerator pump is part number 64-212s. If one measures the metal washer just above the leather skirt, it measures 0.700 inch. Since the leather skirt will compress against the expansion spring, trying to measure the skirt will give ambiguous results. If the metal washer measures 0.700 the accelerator pump should work. Jon.
I measured the washer and I come up with .7115". So is the pump inferior in sizing or is it the 3/4" pump? (again my well measured around .72"-.73" in the bottom stroke area. ) I understand measuring the pump seal is difficult due to the ease of distortion but with slight compression at the seal around the spring area I measure .76" and around .79" loosely.
I do not have a 4131s body in the shop. I did try one of the aftermarket pumps with a 0.715 washer in another Carter AFB that calls for the 64-212s pump, and it works fine. With no offense meant, is it possible you have an incorrect articulation spring on the pump? The articulation spring should be MUCH stronger than the lower return spring. Jon.
I determined that the upper "overload"spring was the same as the lower return spring. I removed the lower spring completely to prove my theory but the problem remained! Yes it gets stuck with no lower spring installed but only after sitting overnight. I have since stole a spring out of an old wcfb that I had...seems to be alot lighter and measures very close to the specs I found. (1.59" long, .025" wire). It just seems the pump is too fat, especially are sitting overnight, it works great when initially installed.
Pretty much out of ideas. This is the first I have ever heard of a leather pump expanding. And we have tested leather pumps with every additive available locally. The only other explanation I have for the skirt expanding would be several years ago, one of the aftermarket pump manufacturers sold a pump with a thicker than normal neopreme skirt and expander spring that looked like leather. It would expand when placed in ethanol based fuels or octane boosters. But haven't seen one of these for some time. Jon.
Jon I opted not to machine the pump as we discussed. I found the area under the seal support spring was plenty to allow the spring in further if forced. I rummaged through some old rochester parts. I found a support spring that was noticeably smaller in overall diameter with the same coil size. I installed that onto the stem and gently measured around the leather and came up with .72" (as opposed to .76")This seemed to slip into the well much easier. I reassembled the carb yet again. The pump shot seemed the best yet. I will check how it works in the morning. Thanks again for sharing your expertise! People like you and our fellow hambers will be the only hope to keep these cars going!
Glad you called. Sometimes a direct dialogue makes a lot more sense than posting and reposting; and glad you now have it working! Jon.
Well I went out this morning and checked the carb, and I had an excellent pump shot! Again thanks for the help.
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