Rough idle and start

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2kids

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Hi folks,
Here’s the pattern on my 71 Dart….I think it’s a carb/choke issue?

It’s variable, sometimes it will start on the first start of the day without even setting the choke, other times I have to actually pump the gas pedal while cranking it over in order to get it to start.

Then, if I’m running a few start and stop errands it will start to struggle to start up and I usually have to let it sit for a few minutes and then pump the gas pedal while turning it over to get it to start.

Yesterday it started up after pumping the gas pedal while turning it over and it was running really rough while trying to warm it up. I took it out on the open road for a nice Sunday drive and it ran great the entire time, which I interpreted as maybe a carb issue.

So, I don’t know…just curious about what you think. Rebuild the carb? I know I’ve seen vacuum leaks mentioned on other threads – not sure how to check those yet but sounds like that might be in my future too.

Thanks,
2kids
 
After a drive on a hot day as soon as you get home and parked let it run,open the hood and remove the breather, reach in your car and shut it off, look in the carb and see if there is gas dripping into the intake..

To check for vacuum leaks on a cold engine, Have a can of W-D 40 in your hands, start your engine and spay around the base plate, if it has a vacuum leak any where it will change in rpm's, if you are running a vacuum advance pull distributor cap, and the vacuum line off the carb clean the line and suck on it and see if it is moving your advance plate, the diaphragm could be leaking.

When it does not want to start then does!! look at your exhaust and see if black smoke puffs out, this is a flooding problem, if no black smoke your carb bowl is empty, do you have a clear fuel filter ? your fuel pump may need to be changed out, allot of different things can do this, even hot boiling gas (vapor lock) in the fuel line.

X2 is all these things check out, It is time for a carb rebuild.
 
Don't forget ALL of the places vacuum runs. A/C/heater controls, manifold mating surface, vacuum canister and vacuum advance.

Slants are notorious for having hot start issues, engine bay heat soaks the carb after shutdown and boils the fuel out of the carb ( flooding ). This also translates into cold start issues because you have to crank the heck out of it the next morning because the bowls are empty.

On my car ( when it had the slant ) holding the pedal wide open during hot start will allow it to start quicker and idle better sooner.
Here in FL, I had to add a heat shield under the carb to get it fixed.
 
Cold start problems are often a mis-adjusted or broken choke. The choke plate should be closed firmly when the engine is cold. As soon as it fires, manifold vacuum should suck the "choke pull-off diaphragm" full-in to pop the choke slightly open (see manual). The pull-off often fails and is cheap and easy to replace. Test it by pushing in, blocking the vacuum port with your finger and let go. If it doesn't stay in, the rubber diaphragm is broken. Even, better test it with a hand vacuum pump.

If you still have points, start reading up how to replace those. You will get smoother running and better mileage.
 
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