Cold start issue

[flaminchiten]

Hi all,

My truck has an issue with cold starting, it will fire right up in the first couple cranks of the engine when it is cold....then it acts like it runs out of gas. It will then take 15 - 20 seconds of cranking before it will start up again. Too me it feels like it fires right up but once it drains the gas in the carb is when it dies. I think the fuel line is slowly draining back into the tank instead of staying full of fuel.

I am 99% sure this is what is happening, what I need to know is where this would be occurring, what would be causing the fuel to drain back down and empty the line?

Thank you in advance.

[4x4orbust]

not sure of the solution, but i am also having the same problem.   i thought it was choke related, but have ruled that out after adjusting it.  then i thought it was the choke pull off, got a new one and still having the same problem.   looking forward to hear others suggestions.

[Lt.Del]

how soon does it die out?

It could be your needle / float in the carb.  

The float goes down when fuel level is low, thus opening up the needle where are the gas come in to the bowl from.  Once the float goes back up, it shuts off the needle. Sometimes the needles sticks in the closed position, thus no gas comes in, or is very, very slow.

Try tapping the area of the carb where the fuel line goes in at, or try changing gas filters there.

After starting up the second time, does it then run ok?  Or does it repeat the cycle, just requiring 20 seconds of cranking?

[flaminchiten]

It dies about 4-5 seconds after I start it up the first time, after about 20 seconds of cranking and starting the second time it runs just fine and runs great once it is warmed up.

This is on a 1975, 454 with a quadrajet btw.

[Lt.Del]

if that's the case, that's not enough time for the bowl to empty.  That shoots down the float/needle theory.

My next guess would be a vacuum leak around carb..either a dry rotted vacuum line or gasket...allowing too much air to come in.  The choke, on a cold engine should be closed to prevent air coming in.  If there is a vacuum leak, more air than needed will enter as if the choke is misadjusted.  Cranking many times to get it going again is a sign of choke misadjustment or air sneaking in from elsewhere.

When you have time, let it idle, then take some wd40 and spray around possible leak points like carb gaskets, vacuum lines, etc.... if rpm's increase from idle, you found a vacuum leak.

[Captkaos]

There is no way that the fuel is returning back to the tank since there is only one line going to the carb and the fuel pump is between it pushing fuel to the bowl.

I would say you have a vacuum leak or your choke isn't working.

[Irish_Alley]

i have that problem and i know my choke aint working  pretty sure it aint a vacuum leak also

[bobcooter]

My 350 with a Q-jet does it too on cold mornings. I pump the peddle twice and it busts right off the first time. I just head off my problem by turning the radio and everything off so it's quite in the cab and then I feather the peddle when it starts to stumble. If I miss and it goes dead, I give it another couple of pumps and it busts right off again and stays running the second time. Seems like every old Chevy I've ever owned acted like that. It's all in your right foot technique! LOL Sorry not much more help than that.