Hard start cold - possible fuel issue

[tip]

I recently picked up an 86 C30 with a 350 and 105K miles. I'm having a hard/no start cold.

It won't start after sitting for a day or so. I can get it running by adding a little fuel into the carb. It dies, I go out and put a little more in. It starts and dies again. I repeat this about 3-4 times. Once I get it going and warmed up, I can let it sit for an hour and it will start right up. Runs great.

The guy I got it from said the gas was 2-3 years old, so of course that's what I thought it was. I ran out the left tank and let the right tank (which was FULL) run down about 3/4 then I added 2.5 gallons of 92 octane, fuel stabilizer, checked spark, cleaned plugs, charged battery, replaced the in-carb fuel filter and drove it/let it run for about an hour and let it sit overnight.

So I go out this afternoon and pulled off the air cleaner before I try to start it. I move the linkage by hand and watch, slim to none fuel squirting out. I do it over and over again and no still not only more than a few tiny drops of fuel and "hiss" "hiss".

So I added some gas to the carb as usual and she fired up after the third bit of fuel added. Let it warm up for 5 or so minutes. Shut it off. Now I look in the carb and plenty of fuel comes out when I manually work the linkage. Starts right up no problem.

So, my question is: Is there some sort of check valve in the mechanical pump or somewhere to not let the fuel drain out of the carb? Fuel should be staying in the carb after its shut off right?

Thanks, I haven't had a carbed rig in a while.

[INSIDIOUS '86]

If its a quadrajet from my understanding the have some plugs underneath that leak after a while and drain the carb

Cold carb starting explained. Basicly when an engine is warm or the weather is warm a carburator will flow fuel and air into the intake in a liquid fuel/ vapor mix. As we know it is the vapors that burn not the liquid fuel. We know that cold weather causes condensation and it does the same to your fuel. The fuel will quickly condense on a cold morning on the manifold walls and floor causing a lean condition. On top of the fact that cold air is denser and makes a more lean air charge as well. This is why stock and some aftermarket intakes have ribs on the bottom so as to direct raw fuel to the cylinders

Your carb is the issue have it checked out
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[tip]

It is a Q-jet. I did find a lot of info about the well plug leaks, drain back and possible evaporation.

Last night after I had it running, I clamped both the soft fuel lines headed back to the tank. I let it sit overnight and went out to check out if fuel is spraying in the carb. Sure enough, it is. Truck started right up. The truck would NEVER start the day after, not without manually priming the carb first. (Or cranking the engine over forever to fill the fuel bowl).

So looks like I may have a bad fuel pump - there must be a check ball or valve in there that is letting fuel back to the tank. (I do have the incarb filter with the drain back valve.)

I'm going to test is one more time tomorrow morning. Then let it sit overnight without the clamps on the lines and see if it won't start again. That will give me total piece of mind that the fuel pump is the culprit.

[INSIDIOUS '86]

It's a $20 dollar part so no harm in peace of mind. The float bowls retain fuel though so there is no way for that fuel to drain down the line
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