The procedure: On a cold startup, I pump the gas about 3-5 times, pull the choke, and turn the key. Usually catches right away, revs to 3k, then starts to stumble, idle falls, and the engine dies. It's like someone cut the gas off.
I've tried some variations to keep the car running; the only way is to feather the pedal to keep the rpm's up, way up, around 3-4k or it goes downhill fast.
After it runs for about 20 seconds, its fine and idles with the choke pulled. Any ideas?

 

after I changed my spark plugs, on a cold startup, I turn the key, get the choke out, do not pump, and it usually fires right up. If that doesn't work I pump it once and then it fires right up. Maybe you're flooding or need new spark plugs? or some other carb related issue? too rich? too lean?

Or maybe Carl modded your carb and he's to blame?

 

there was a post earlier about a guy pulling the bowl vent connecter off and the idle strainterned up cant remember who or what though should ask carl

 

Mine will do that, but only when the temps are really freaking cold, like -25 to -30 Celsius, right now, as a matter of fact. It's only rarely and it usually happens because I don't have the proper amount of choke, be it too much or too little.

 

i think it's plugs you probably fouling them when you pump it 3-5 times and pulling the choke, i normally just have to pull the choke and let it run for a bit or course it dosen't get to god awfully cold here in southern IN...just my 2 cents

 

i dont need to pump my biatch neither she fires rite up , this morning -2 in kansas wind chill -1o. shes got no cold start assist , and a cold air intake, was still cranky though driving out.

 

Just curious. When it dies, have you checked the float bowl levels to see if there is fuel in them?

Your sig says "modded carb". What mods?

How does it run after warmup?

 

I'll do that and post what I find. Should I get out of the car after it dies and check the float levels? Or check them first thing before I start it?

Sterling did it for me; mechanical secondaries, larger primaries, larger pump shot.

Fine. Just shitty gas mileage and backfires; the usual

 

Both. Before you start it, check the bowl levels. Then after it dies, check them again. Maybe it's not part of the problem, but why not make sure?

Oooh. A sterling carb. Cool. Never talked to anyone other than sterling who had one. I'm not yet worthy of one.

Larger pump shot? Maybe you are draining the bowl down too far when you pump it several times in the start up procedure. Did you replace the stock fuel pump and add a pressure regulator?

 

It's not a Sterling Carb. It's a "Partially Modded" rebuild.

The backfire is from the lack or incorrect adjustment of the decelleration dashpot.
The shitty gas mileage is life.

You should not need to pump the **** outta her like that. You have nearly half again what the original AP capacity is, so for every two pumps, you're really giving it three.

I don't recall if you have a full choke or not. But with mechanical secondaries, if you're going passing half way with the pedal, you're opening them, thus negating the effectiveness of a choke.
You're probably finding it necessary to do so because you're drowning the engine in fuel by pumping too much before/during starting.

 

There were a couple guys, but they bitched about bad fuel consumption, so I had to kill 'em.
-You understand, right? I couldn't have the first thing said about my carbs here being negative.

 

Hey, I don't see bitching about fuel consumption as a complaint about your mad carb skillz. I always assumed our cars drank fuel like my grandmother sucked down whiskey.

I'm just happy I figured out that pumping the pedal so many times at startup would lead to low float bowl levels after the AP mod. Take it as a sign that someone's learning from you.

What's now become clear is the difference between a partially modded carb and a Sterling carb. I shall never make the mistake again.

 

While the ignition is being turned on, the pump is running for a second till the relay shuts off. This replenishes the float bowl behind the AP housing from wich the AP gets it's fuel.
Unless you have a no start situation combined with an electrical problem, you should experience no depletion in the bowl.
Initially you rely on the main circuit to start the engine and then want to let the pedal up and have the idle circuit take over. The idle circuit just dribbles a constant, metered amount of fuel (mixture screw) to combine with a constant, metered airflow (idle speed screw).
When the car is cold, the fuel is dense and fails to mix very well with the air. It wants to condense into droplets. Once it's warmed up, the fuel stays vaporized much more easily. You tune your idle circuit to run optimally while warmed up because no matter the start up temp, the engine will eventually reach this temp.
But if you could change the idle speed and mixture easily to work optimally with the engine really cold, and then change it again to work optimally when the engine is halfway beteen cold and warm, and then change it optimally to when the engine is warm...
...well, that's what the choke is actually trying to accomplish.
We all know how touchy and difficult to diagnose the idle circuit can be if something is not right.
The properly tuned choke is entirely dependant on a properly tuned idle circuit.

As for the differences in the Sterling Carb and a Partial Mod Nikki, there are many.

 

That was a very nice way to tell me I was totally wrong. Losing your touch?

Thanks for the clarification.

 

That's exactly how I started my 7 for the longest time, until recently.

A friend of mine told me that even though it's carburated I should still kick in my clutch to help the engine turn easier.

Pull out the choke, turn your key, and if it won't start pump the gas pedal once and she'll start right up!! (exactly what cdrad51 said)

 

Yeah, I forgot to mention I always hold the clutch in. If I let it out this too will kill the engine.
I never pump the gas enough to open the secondaries. I only give it 3 or 4 half-pumps.
The idle circuit is about right; 3 1/2 turns then tune the other screw to 750. Thats how you set the idle circuit?
If we get a warm day here I'm going to take a look at the choke.