Troubleshooting

This could be caused by the distributor, but we will only address the carburetor.

Hesitation is generally due to the accelerator pump circuit.

• The pump could be bad - replace it.
• With the engine off look down the carburetor and pump the gas. You should see 2 good squirts coming out of the main discharge. - If you don't get 2 equal squirts then one or more passages are plugged. Spray carburetor cleaner through each small passage, including any on #31 & #36. Make sure the spray goes through each passage. Ethanol can leave residue cleaners will not get out.
• Remove the pump jet housing. With fluid in the pump well, press down on the accelerator pump. Fluid should rush out of the main discharge. If it does, then the passage way from the pump well to the main discharge is OK.
• The check ball in the main discharge may not be working or missing - There should be a check ball and a spring, or a check ball and a check weight, or a check weight with a pointed end. See # 37 in the illustration. Depends on which AFB you have.
• Maybe the check weight, or check ball isn't sealing - Hold down the check ball or check weight with a brass drift punch and press down the accelerator pump with fluid in the carburetor. We use mineral spirits. You should feel some pressure which means the check ball is doing it's job. - If you get a leak, tap on the check ball a few times with the brass punch. It doesn't take much pressure to form a seat for the check ball.
• Make sure the gasket under the pump housing #36 fits flat. Sometimes a new gasket will need to be trimmed so that it lays down flat.
• There is an off idle circuit that is often missed. Look for a hole just above the idle mixture hole inside the bore. Blow air through the hole to see if air gets all the way through to the top of the carburetor. This is used when transferring from idle to the accelerator pump circuit and can cause some hesitation.

https://youtu.be/kskxkBvBl9c

Customer Q&A:

Q: My car bogs when I floor the pedal. What do you suggest?

A: Does it have a choke? It’s possible the choke may not open all the way, not allowing the secondary’s to open properly. Also the passages in the secondary clusters may be clogged. Make sure they are clear by running small wire through them.

Q: Sorry to bother you. I bought kit 4011 for my 1958 Cadillac Eldoradro, Carter 2862S AFB carb. Can't get car to come off idle, wants to die. Warm, choke off. Idles O.K., 500-850 RPM O.K. But when I push the accelerator to increase the RPM's above 850, it wants to die. If I coax it past this spot, at higher RPM's it seems fine. A stream of fuel comes out the two accelerator pump jet nozzles when I depress the throttle, so I think the accelerator pump is O.K. I've adjusted the two mixture screws. There is a big air adjustment screw located between the two idle mixture screws, I tried to adjust that also. (But I don't actually know the procedure for this air adjusment) Once it starts getting past the stumble, I notice drops of fuel coming out of the primary venturi's, and dropping down onto the throttle buterflies. (I would think it would be atomized, not drops?) I've disassembled the carb a couple times, the float bowls are about 1/2 full. I'm stumped, I didn't have this problem before I rebuilt the carb. I didn't remove any shafts or butterflies. I would appreciate any ideas you have to offer. Second update: I should have checked this before I sent My first e-mail. My problem is a lean condition. If I pour a lttle gas down the carb while it is stumbling, it stops stumbling and smooths out. So the question is: What causes a just above idle lean condition? Third update: I fully closed the big air adjustment screw located between the two idle mixture screws, and this helped alot. I moved the accelerator pump rod down to the bottom hole, and this seemed to help some. I stll have an off-idle stumble, but it's drivable, it doesn't try to stall, just stumbles. The stumble is smooth slow acceleration, not punching it.

Follow up: I took it apart again, and found a piece of debris partially plugging the small brass tube feeding fuel to the primary venturi, (the small tube inside the bigger tube with holes in it) The clue was, just above idle fuel would drip out of one venturi, (the bad side) No more hesitation, and I was able to open the air adjustment screw to set the idle speed.

Q: When I pump the accelerator the main discharge doesn't spray until the throttle is partially opened.

A: One common problem often overlooked is the electrical system. The distributor advance in particular. Make sure it is operating as it should. Here is a list of possible problems (not in any order):