Re: carburetor flooding

Posted by Joe on April 06, 1998 at 13:03:27

In Reply to: carburetor flooding
posted by Wayne Parker on April 04, 1998 at 22:29:10

: I have a Zenith 2 carburetor that seems to flood very easily when you are are starting a warm or semi-warm engine that has been sitting for an hour.(Cold starting is fine.)Carb was rebuilt several years ago and this was not a problem initially.When warm, the engine is very reluctant to start and if it doesn't catch in the first 3 or 4 seconds of cranking, there will be a fair bit of gas dribbling out the throat of the carb.Then, the only way to start the car will be to hold the gas pedal to the floor and crank.It will then always start.I am assuming that the problem is carb related.What could be causing this?I believe that my starting technique is OK.
Wayne
Sounds like you have the dangerous "sunken float" disease or one of it's variants.
You'll have to take apart your carburetor to determine if you have problems...
I think you can do everything below with the carburetor in place on your intake manifold.All done with the lower half of the carburetor unbolted and removed.
1. Check to see if you have a liquid inside your carburetor float.You can take the float off by removing the small brass pin it pivots on.If you hear sloshing around inside it is likely you have a pinhole in the float and this causes it to float too low causing gas to overfill the float chamber.Solutions are to find and fix the leak with a small dab of solder, fix by painting the float with shellac or permatex, or replace with a recycled used or new reproduction float.(I would be interested to know if anyone has experiences with reproduction floats, either good or bad.)
2. Check to see if the needle valve closes fully.With the carburetor lower half off and the float back in place, see if you can stop the flow of gas by holding up on the float.You should be able to shut off flow completely.If not, the valve is leaking.This can be caused by a little piece of grit in the valve or simply a worn valve tip or seat.You can clean out the offending grit and it will likely reappear but another better solution is one of the newer Gros-Jet ($4.50) or neoprene tipped needles ($8.95).I prefer the neoprene as closest to the original.
3. Marco at his barnyard workshop site at www.concentric.net/~marcot/workshop/carb-1.htm
has a good description of another problem with has to do with the float hanging up against the needle.This is one I have previously overlooked myself.You'll want to examine the float while it is off for #1 above.
4. Another possible source is the float is set too high in the body.When the float valve is fully closed and the float is at it's uppermost position, the seam on the float should be parallel to the flange face between the two halves of the carburetor.Too low and your car performance suffers, too high and you leak gas.You can bend the float on it's pivot to change the height setting.Since you describe your car as not having had the problem originally, this as root cause is unlikely.
I heartily advise you to find the reason for your leakage.It is not safe to have gasoline leaking or running around uncontrolled any more than you would with a modern car.
It should not be necessary to shut off the gas at the inside valve each time you stop your Model A.By doing so you prematurely wear the inside valve and will eventually have a little drip of gas inside the driver's compartment at the valve packing which is even more unsafe.
If you want to read further, there are a couple of good books written specifically on the Model A Carburetor.*The Model A Carburetor* by Paul Moller is good ($6.00) and available from the many parts suppliers.
Hope you can get her running well.Work Safely with the engine cold, well ventilated and with a fire extinguisher handy. Do it outdoors where if the unthinkable happens, at least you'll only lose the one car.
Best regards,
Joe

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