1972 F-250 360fe 2bbl carb hesitation

[LGreen72F]

I have been trying to fix a bad hesitation/stumble for a long time now. It occurs on acceleration about 1/4 to 1/3 full throttle. I have replaced fuel pump, fuel lines, fuel filter, checked timing many times, rebuilt the carb, got a tune up, got all vacuum leaks fixed but still have the bad hesitation. Idles very smooth and runs fairly good (besides the hesitation) I have taken it to a mechanic and they were not able to fix it. I have tried almost everything yet am still stumped. It is a 360ci with a 2bbl carb and a c6 automatic.

[Ren]

I know you say the carb was rebuilt. But it sounds exactly like an accelerator pump issue to me. Also, a diaphragm doesn't have to look bad in order to be bad.

[LGreen72F]

I know you say the carb was rebuilt. But it sounds exactly like an accelerator pump issue to me. Also, a diaphragm doesn't have to look bad in order to be bad.

hmm... today I did take the accelerator pump diaphragm out and had a look at it and it looked fine but decided to go down to the local auto part store to get another just in case, but the store said they didn't have any of the same kind and could not order any.

[1972hiboy]

I know you say the carb was rebuilt. But it sounds exactly like an accelerator pump issue to me. Also, a diaphragm doesn't have to look bad in order to be bad.

hmm... today I did take the accelerator pump diaphragm out and had a look at it and it looked fine but decided to go down to the local auto part store to get another just in case, but the store said they didn't have any of the same kind and could not order any.

You wont be able to buy individual parts for a carb anymore. it would have to be a whole new kit to get the diaphragm. but agreed it sounds likes vac leak or carb build/adjustment

[Mach428]

Remove your distributor cap and remove the vacuum advance hose at the carburetor. With the vacuum hose connected to the vacuum advance, start sucking and watch the breaker plate. I would bet either the advance is bad or the breaker plate is stuck

[idaho_cowboy]

A friend recently had the same problem. I think points were suspect.. Might be worth a look. Swap them out and adjust to spec ?

- Joseph

[LGreen72F]

I just recently gave it a tune up and it seems to be advancing just fine, but ill take a look just incase

[LGreen72F]

Sorry for taking so long I've been so busy. I took the truck in to a local mechanic just to have them take a quick look, they said points are spot on, adjustments are perfect, timing is exact. They said it's definitely a carburetion problem. Well, I decided that since I still had the warranty on my last rebuilt carb, that I would take it back for another. So came home with the same type rebuilt carb and all, put it on and adjusted it as needed and it ran perfect, no hesitation and it has more power. So it seems it was maybe just a bad carburetor this whole time? Though I've noticed it runs perfect when the temp guage is up to operating temp but still hesitates when not fully warmed up. I think this is just a choke adjustment needed to be made and I am experimenting with it now. For now, thank you guys so much for your help! If you have any suggestions on what to adjust or anything, let me know.

[LGreen72F]

After some experience of the new carburetor and driving and inspecting, it seems that the accelerator rod may be bad... When i slightly push the accelerator or lightly let it off, the rpms are higher than usual whether in park or drive, and i have to let the accelerator slam down for it to drop to the normal rpms... so another bad carburetor maybe?

[Ren]

Before anything, ensure you installed the throttle return spring correctly. It also doesn't hurt to check for vacuum leaks. But this problem sounds like the 'dashpot' thingy is out of adjustment. It's a disc shaped object with a plunger sticking out of it. I won't get into it here, but it's purpose and usefulness is dubious at best. Unscrew it until it is incapable of influencing the idle speed of the engine. Or remove it completely and give it to somebody you hate.

It's also very important that you tune the carb while using a vacuum gauge. If doing these things doesn't solve the problem, the throttle plate shafts on the carb are suspect and that requires attention from a reputable professional.

And that's the reason why I NEVER buy a rebuilt carb from ANY auto parts store.

[LGreen72F]

Already messed with the dashpot alot, moving it in and out and doing adjustments but that doesn't seem to help, and had all supposedly had all vacuum leaks fixed by a professional, but thank you for the suggestion. And yeah, I dont much like buying rebuilt carbs from anywhere now after these experiences, might just convert it over to a brand new 4 barrel with dual exhaust and fix the whole problem!

[LGreen72F]

Also, just another bit of info that might help determine the problem, the hesitation also happens when i'm already going down the road, for example, i'll be on the highway going 55 and take my foot off the accelerator, then sometimes (not always) if I push it back down it will just cut out for about 1/2 a second then catch again. It happens going any speed sometimes.

[Ren]

Your text reads very much like what was going through my mind during my learning phase of dicking around with a "rebuilt" carb.
The likely "problem" is that you have a 50 yo. carb that needs more than a casual, parts-swapping rebuild in some dark, slavedriving, meatgrinder hell-hole of a facility where the only thing that matters is groveling to the Human Resources department.

The person who "rebuilt" your carb was likely a disgruntled, angry, 40-something yo. misandry-driven lesbian with five big dogs at home in a squalid, nasty apartment and all of the usual baggage of a person who's greatest accomplishment in life is to stay clean and sober.

About 5 minutes after I installed and tuned a new Holley 350, I couldn't dunk my "rebuilt" carb into a trash can too soon to satisfy me.

Another thing to consider is you need to accurately assess the overall condition of the internals of the engine. You'll regret it if you go through all this time, $$$, and trouble over an engine that is nearly worn out or has other issues anyways.