I need some help diagnosing the problem with my carburetor.When after being stopped at a traffic light or intersection, the car bogs down duringacceleration before lurching forward. I have controlled this by pumping thepedal lightly as I pull forward. I havechecked for vacuum leaks and changed out the carb gasket and some vacuum lines,there is no improvement.

Where should I look now?

 

fuel filter

 

Thanks

 

Accelerator pump?

- Eric

 

I'll change both out. First the filter and then the pump.

Thanks

 

X2. It almost certainly is not fuel pressure/filter problems. Those would be far more evident during W.O.T. blasts, where you are stressing the flow limits of the pump and filter. This rarely shows up at off-idle conditions where the float bowl is full.

If the accelerator pump cup is worn or the linkage is worn, you should probably just rebuild the carb first, then adjust the pump linkage to spec.

 

X3 on the accelerator pump. If your using fuel with ethanol it will/can eat a pump cup not designed for it. If the acc. pumps bad it will show as a lean off-idle or tip-in dead spot condition, which it sounds like your experiencing. Look down the carb while actuating the throttle, engine off. You should see two strong squirts of fuel in the primaries from the very beginning of the pump stroke to the end (WOT). If it needs a rebuild send it out for a modern updated rebuild. Or if you DYI spend your money wisely on a USA made kit from Cliff or some of the other higher-end re-builders. Furthermore you could be experiencing boil-over, again due to today's sheet gas and an old school float level spec setting. This would show up as a rich condition which will cause tip-in, rough(er) idle and off idle problems. Read your plugs and exhaust to see if its lean or rich. With ethanol the float level needs to be adjusted slightly lower than the old spec to compensate for the ethanol's lower flash/boil point.
It sounds like you've check the simple stuff first...vacuum leaks will cause this same symptom. There's no EGR on this engine is there?

 

Now this is excellent advice.

I was leaning towards a bad fuel filter since the car has sat for a while. But the accelerator pump was also on my mind.

I had no idea about the adjustments required for todays sheet fuel. Thanks for the info.

I am a novice so every tiny bit of information is greatly appreciated.

Thanks all

 

I agree that the fuel filter is a low percentage on this ... I suggested it only as the next thing as most other options involve tearing into the carb. It's generally a good idea to eliminate all the other options no matter how low percentage before launching into a rebuild. Have you had any trouble starting the car when cold recently?

 

Mildly accelerating, right, not very much carb opening?

 

Yes, I am having trouble starting the car when it is cold. I sometimes need to pour a little gas down the carb before firing it up.

 

That's the killer. Get yourself a rebuild kit, you're going in.

 

I just picked one up at NAPA.

 

They're not really a hard rebuild. Not really all that much to them, despite their reputation. It's worth your time to pick up some JB weld before you start too.

 

I had the same symptoms with my 2bbl. I bought a rebuilt one and that took care of that issue. I did open up my existing carb and the ethanol and carbon made a mess of it.

I also had problems with starting in the morning if it sat. I was told it is typical of these carbs. I can't remember the model number but is is different than the rochester that is on my camaro. that carb does not have a problem of leak down.

 

What is leak down?

 

this explains it:

http://www.hotrodders.com/forum/carb...wn-206629.html

the gas is not retained in the fuel bowl after a period of time. I know if I don't drive my car after 3 days, I have to pump the gas pedal more than I would if the car sat for just a day.

 

Or you could just have a porous rubber hose or two between the gas tank and the fuel pump.

- Eric