What makes a carb go bad? I replaced the carburetor in my truck two years ago and it was running fine until last week. First a lot of carbon came out of the tail pipe. Later it would stall and surge. Now it is very hard to start. Is there an easy fix or should I replace the carburetor again? It seems like it is flooded.

Something stuck in the needle valve................

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Is the choke sticking closed or the choke pull off not working?

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50 chrysler,54 Plymouth, 64 Valiant conv 4 speed, 66 Valiant V8 wagon, 70 Challenger R/T 440+6 conv 4 speed,80 Colt, 98 Neon ACR,84 Honda V45 Magna
Taking care of 57 300C conv,48 T&C conv. Missing my 67 GTX and 36 Ply coupe

or a sunk float

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

r u positive the problem is really the carb?

Ditto. Carbs usually don't just fail. I would suspect the coil before the carb.

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Casually looking for a Clifford hyperpak intake for cheap.

Thanks for the replies.

I'm going thru something that could be described as u did. my trouble is the vacuum pod on the distiributor.

Thanks for your help guys. I will check these one by one today.

Sometimes carbs can go suddenly very bad due to an internal crack in the casting where you can't see it.

A lot of times a re-built carb from the auto parts store is bad. Most often the throttle/shaft is worn out. It may take some time for it to fail. Glad to see you have the carter carb-the Holley is not the best. As you said that you are getting a over rich I would look at the choke to make sure it is not staying closed and opening 100%.

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50 chrysler,54 Plymouth, 64 Valiant conv 4 speed, 66 Valiant V8 wagon, 70 Challenger R/T 440+6 conv 4 speed,80 Colt, 98 Neon ACR,84 Honda V45 Magna
Taking care of 57 300C conv,48 T&C conv. Missing my 67 GTX and 36 Ply coupe

Black smoke generally points to an over rich fuel mixture problem. Rich mixture will cause chugging, black smoke, stalling, fouled plugs, and hard starting.

There are several reasons for carburetor failure, or rather carburetor problems. These devices are complicated and yet simple in theory; mix fuel and air continuously. In order to mix fuel with air in a way an engine can utilize it under many operating conditions things get more complicated.

Firstly to start a cold engine it needs a rich mixture, a properly operating choke mechanism handles that task. If that choke is out of adjustment or its controlling devices malfunction and allow it to stay on too long, the engine will belch black smoke, idle & run roughly if at all, and return poor fuel economy.

Start with an “over nightâ€￾ cold engine, remove the air cleaner, and by hand, turn the throttle plate to wide open and quickly release it. Observe if the choke plate snaps closed firmly, and throttle advances to high idle position on the high idle cam.

Next start the engine, dose the choke plate open about a quarter of an inch as soon as engine is running, this is good; or dose it stay tightly closed , bad—this indicates that vacuum pull off is not doing its job.

If choke opens that 1/4th inch, dose it slowly continue to open as coolant warms to operating temperature allowing the throttle tostep down the high idle cam; yes = good; no opening, the electric, or bimetal spring in heat stove is not doing its job. Clean & adjust its pivot points, or replace it if the spring is broken.

Secondly, proper fuel level in the fuel bowl has to be maintained for a correct air-fuel mixture to be delivered to the engine through all rpm ranges.
Several causes can cause improper fuel levels: poor needle seating or sticking needle; sunk float; poor fuel delivery caused by a fuel pump, or filter problem.

Thirdly crud / sediment collecting in the carburetor’s passages can cause all sorts of problems, but where black smoke is a symptom, a needle valve could be held open by a flake of rust and will cause a rich condition. Also if the internal anodization has been compromised from previous improper cleaning, today’s blended fuels will cause oxidation on those surfaces, and in some cases can plug these passages rendering the carburetor useless.

So from easy to more complicated: determine if the choke is working correctly as outlined above beginning with a cold start; see that float is floating; and needle valve is sealing when float is floating.

I have read on other carburetor sites that with this blended fuel, some carburetors require a rebuild if the engine has not been run for several months, or been stored over winter.

Vacuum timing advance won’t cause an engine to run rich and make black smoke.

If you find that the carburetor is up to snuff, than we can look at other possible causes.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

This is the info I was looking for wjajr-thanks. Time to put on the coveralls and get to work.