Running Rich at Idle, stalls, hard to start after.

My car has been running great but ever since I took it out on the highway a couple nights ago I have a problem after the car gets hot it seems.

All day the car ran great on trips to the store, no probs, idles at the stop light perfect. Smooth crisp acceleration. Then out of the blue, just like a few nights ago, it starts idling rough at the light and I have to brake and throttle lightly to keep the rpms up to 700 so it stays running. When i dont it quits and the only way i can get it started again is by holding the pedal to the floor and unloading it while I crank, then it finally starts and coughs and I have to rev it to clear it out. it will idle in park at about 800 rpm. Its like it is flooding or something, but i dont know if its flooding at the float or if its dripping off the jet wells on the bottom. If I turn my idle screws all the way in and then back them out only 1/2 turn then it will run, any more than that and it will stall. If i unplugg a small vac line it runs no prob because it has more air to dilute the richness. But why is it flooding? It is wet around the top of the accelerator pump and the gasket is wet in the front, seems to be creeping back to the back a bit. It must be flooding at the float.

I did rebuild it and it ran great for a month, until now. I adjusted the float since this happend and actually raised it to 5/16. It was too low. I replaced the seat and the float needle, but not the black float.

Questions:

Can that black float go bad?, why does it happen only sometimes? Could my power piston be stuck open?

please advise.

 

I know some of the floats absorb fuel over the years, become heavy, and leave the needle open.

 

When I had a Q-jet this would happen to me occasionally. The problem was trash would get in the needle and seat not allowing it to open and close fully. It would run terrible and spill gas all over the engine when this happened.

The cure was to take the big fuel line nut off the front of the carburetor and then place a screw driver through the bowl vent which would press the float down. Gas will then back flow out the fuel inlet. Ran fine after that.

 

Interesting. I dont get any black smoke and there is no gas leaking onto the manifold, its a little wet around the accelerator pump shaft and the air horn gasket looks damp in the front.

Ill get a new filter from napa tomorrow and do the backflush thing you said.

What is vapor lock, could that be what is happening?

 

I don't think it's vapor lock.

You mentioning that you had to floor the pedal and let it clear out for a few seconds is a classic example of being flooded.

 

Vapor lock is when the gas gets hot enough to boil.
Does you carb/fuel pump/fuel line get hot?
Your symptoms do sound more like a flooding situation though.

 

ya its flooding. but why. other than that the car runs perfect, if I could jsut fix this. It stranded me the o ther night when i was testing out my new radiator.

Bad float
crap under seat
defective filter letting crap in
defective float needle
bad float needle geometry, binding in hole
bad float setting ( i set it so the distal end is 5/16 from the top of the casting.)

what are those black floats made out of? how could they fill up with gas or lose their buoyancy? Air horns coming off tomorrow.

 

Please don't open that thing until you back flush it first, and then test it.

 

alright, ill buy a new filter, take the big nut off, push down on the float with a screwdriver until all the gas comes out the the inlet, then ill replace the filter, put the big nut back on and start it up. and if it dont work, ill pull the airhorn.

 

could it be slow dripping from someplace else above the fuel bowl? from some passageway or something?

 

Sounds good.:TU:

 

Sorry for the late reply....

BINGO, yes there are plugs on the bottom of the float bowl. 90% of the time these leak and cause hard starting, rich running and other issues.

I use epoxy to keep the plugs secure.

 

but why would it wet on top if it was leaking out of the plugs? besides I already roughed them up and put epoxy on them when I rebuilt it.

 

You must have another issue, at least you know that is not the problem.

Likely a bit of junk caught in the carb like Cason suggests.

 

I hope so, it really does it when the engine is hot, could the gas be boiling in the bowl and spilling over?

 

I would post in the q jet section... there are carb experts there

 

I already got a new pump from cliff and installed it, works great. Ill check the float setting again but Ive already checked it twice. 5/16 from the top of the casting to the top of the end of the float. It does this when the engine is hot. When its cold it runs good for about 45 min then starts having this rough idle, stalls and have to unload it to start it, the top is wet but no gas on the intake.
if i lean it out by pulling a small vac line, it smooths out and runs fine. so it def too rich at idle.

 

its not running hot anymore since i replaced the radiator. It was running about 180 when it happened. If the fuel is getting too hot that could be it. A thick base gasket thats a good idea, im going to try it. Thanks Larry. Good news, the timing is perfect now thanks to you, much appreciated.