It dosenot matter how many times I pump the gas after it sits for 6 or more hours. It cranks forever before firing. After about 3 sets of pumping the pedal and cranking the engine finally fires. I have a carbed 305. Any Ideas will help.

 

One pump should be all you give it, and all it should need. If it doesn't start with that, then start going over the basics of the choke operation.

The basics:

The choke should be open when the car is warm. When you shut it off and the engine cools off, the choke will partially close as the choke thermostat puts tension on the butterfly, but not all the way. It will be held partially open by the fast idle cam. When you give the accelerator one pump before you start it cold, the fast idle cam engages and allows the choke butterfly to fully close. Then, as the engine warms up after starting, the choke thermostat opens the choke butterfly and disengages the fast idle cam (the throttle has to be opened slightly in order for the fast idle cam to disengage).

So, start by taking the top off of the air cleaner when the engine is cold and open the throttle slightly (the ignition can be off for all of this). If the choke butterfly doesn't snap shut, start figuring out why.

 

Could it be that the carb is leaking and after 6 hours or so the fuel is completely drained? If thats the case, it would take a little bit for the bowl to fill and start flowing fuel for the engine to start, no? I'm not pretending to be an expert or trying to contradict five7kid but if I had that problem, thats where I'd look first.

 

That is a possibility. But, if only talking 6 hours, at least some of the fuel should still be in the intake manifold.

 

In the past two months I had the carb replaced and tuned professionally, new cap, new rotor, new plugs, new wires, ignition timing set correctly, vacuum wires are correct (good vacuum lines). If the engine is hot it will fire right up, no problem, its just when it sits for a long period of time is when I have a problem.

 

What kind of "professional"?

Need to start with the basics and work from there - Choke? Fuel? Spark?

Don't tell us what you've replaced, tell us what you've checked.

 

I ment an ASE certified mechanic as being the profressional. I personally checked the carb regarding the choke and it closes with one pump of the gas pedal and it opens as the car warms up. I dont think I have a fuel issue because before I replaced the carb I had the same starting issue that I have now. I definitly got plenty of spark.

 

Stock carb?

 

It is a remanufactured rochester quadrajet stock carb.

 

I have exactly the same problem with my car. It worked perfectly until I ran out of gas once. Every since then, it is hard to start cold. Could it be that something in the fuel pump (back flow valve? diaghram?) got wrecked by things at the bottom of my gas tank?

 

Well I owe you an apology, my choke worked fine but my high idle was not set that is why my car would not fire up as quick as it should. I worked on the high idle today and she fired up farely quickly, better than before.

 

How high is the fast idle? It should be around 14-1600 rpm cold.

 

According to my chiltons manual my fast idle should be at 2200 rpm cold. I think that is way to high so I dropped it down to 1600 rpm when cold.

 

It will go up as the engine warms up untill you kick off the fast idle by tapping the gas. 2200 is normal for a warmed up engine still running on fast idle.

All that really matters, as far as fast idle goes, is that the engine speed is high enough and the choke is rich/lean enough that the engine can run somewhat smoothly on its own untill its got enough heat in it to idle normally. Some engines can do this at quite a bit lower speeds than normal, and some need to run faster than normal. My (heavily modified) 350 with the 750 choke'd double pumper can start ice cold and fast idle with the choke on at 1000 rpm and be perfectly happy doing it - no chugging, popping, spitting or farting back. Only drawback to this is that it takes a long time to warm up - thats why I set it to fast idle at 1400 anyway.

A higher fast idle (within reason, of course) is a good thing, because the engine will probably start easier and it will warm up alot faster. Thats why modern fuel injected cars, like my '97 LT1, take forever to warm up... they start and idle right down at 900 rpm or so - not a good way to warm up quickly.