Looking for a little help with the hesitation on my 1960 283ci small block Chevy. Looks like the accelerator pump is not squirting enough fuel -but why? I took the carb apart and cleaned it. I could make the accel pump squirt fuel ok on the bench. Here are a couple of things I wonder about: 1. Is there an issue with the float level which is not keeping enough gas in the carb to prime the accel pump? 2. Fuel pump looks kind of weak -but once the revs are up it seems to keep up. 3. I can wiggle the rod that holds the ****erfly valves, so I think there may be a leak there. This is a Rochester 4 Jet. Here is a video: http://www.youtube.com/watch?v=Qd1SxSegO3k Should I just figure this thing is worn out and buy a Holley? Thanks in advance for any input. Kelvin
Accel pump is either worn out or stiff from new gas blends. Get a kit first, before going further. There could be other issues as well, but you need to fix that accel pump first.
They made a few different diameter acc. pumps for those, and the rubber ones that come in the kits usually wont fit right or just wont work.Leather ones are better for these. Also the rod that actuates the pump lever is normally worn sloppy and can use tweaking, and the pump height adjustment is a little more picky with your 4GC. Make sure the pump cavity is able to fill back up, as in float level and slot in the bowl.
Thanks All. I am getting a kit from NAPA today, but I am afraid it will just have the rubber seal. I had the carb rebuilt just a week ago. I paid $125 and the turn around was fast -so I thought it was a 'no-brainer'. The guy did put a better base on it than it had, but .... I will take a good hard look at the pump this evening. Probably get a fuel pressure gauge too -can't have too many tools.
A few things to check- Does it have a small round screen in the bottom of the bowl near the accelerator pump well? If so make sure this is clean, the pump well fills through this screen and it's easy to overlook during clean up. Is the check ball in the bottom of the pump well? This ball acts as a check valve allowing the pump well to fill then closing (when the pump strokes) to keep fuel from just pumping back into float bowl. I've seen these missing or stuck in the bottom not allowing the pump well to fill properly. Is the output check ( the T shaped piece with the spring and ball) installed properly? This keeps fuel in the output side so the pump doesn't have to fill this area everytime the pump strokes (causing a delay). Pump material- I've had zero luck with the plain rubber ones with todays gas. It seems in no time they're rolled around the wrong way not doing their job. The few leather ones I've been around work OK but I don't know a source for getting them new. I have had good luck with Viton, I have bought them separately in the Standard Hygrade brand.
Just finished reading a post that had no resolution, figured I better find mine and errrr 'resolute' it. My major hesitation problem turned out to be the accel pump, I did not change it just took it apart and put it back together. -I guess it was binding a little. FYI, I could not find a leather one, I think mine was just black "rubber". It was probably Viton, but I have no way of knowing. I still had a minor hesitation after fixing the accelerator pump, but I was able to fix this with timing and idle speed adjust. The car is running like a top now. Thanks for all of your suggestions. Kelvin
Is that a second hole in the flat linkage on the pump? If so put the rod in the hole nearest the pivot. Also the pumps fuel level is the same as the carb level, I think. Make sure the fuel level in the carb is at spec or high enough.
I have narrow my own hesitation issue to the fact that the check ball is wedged down in the hole thus it never fills back up with fuel. Are there any recommendation you have to get it out? Or is the carb toast now? I've tried heating it up and banging it to try to get it out but its wedge down there good.
Probably going to be difficult to find leather pumps, or kits containing leather pumps locally; but most are available mail order. Jon.
Place the empty bowl upside down on a flat pan in a toaster oven. Roast lightly at 425 degrees for about 10 minutes. Let cool naturally. If the ball is not in the pan, keep the bowl upside down, place in a ziplock bag and place in your freezer overnight. If the ball is still in the bowl, take a plastic mallet, and striking UP, strike the bowl with the bowl upside down. If all this doesn't work. Call me at 573-392-7378 (9-4 Mon-Wed central time). There is a sure way, but it is messy, requires some special tools, and a LOT of typing. I will be happy to explain over the telephone. You can type it here if you wish. Jon.
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