Cold start issue

[BDC90]

Old Q-jet 1971. Runs good idles good starts when warm right away. Cannot get it to start cold without a tiny sprits of fast start. Carb rebuilt , settings double checked. There is some primary shaft play but it returns to 650 rpm when I let of the throttle. Is rebushing the shafts really gonna fix this? It doesn't seem like that little bit a vacuum leak would have that much negative affect with choke on during cold start. Anybody got any ideas? Accelerator pumps down both holes (4MV) , no hesitation when the throttle is blipped.

[geezer#99]

When you first pump it to give it some fuel and set the high idle, is the choke closing all the way?

[71CHEVYSHORTBED402]

Originally Posted by geezer#99

When you first pump it to give it some fuel and set the high idle, is the choke closing all the way?

That was my first thought.

Does the OP have the original cold start system, thermostatic air cleaner, riser, divorce choke and such?

[RustyPile]

If the choke is closing all the way, my first thought is metering well plugs are leaking..

[BDC90]

Originally Posted by 71CHEVYSHORTBED402

That was my first thought.

Does the OP have the original cold start system, thermostatic air cleaner, riser, divorce choke and such?

All original so I'll double check the choke blade. The well plugs are the later style so pretty sure they don't leak.

[BDC90]

Re-adjusted choke arm, it may have been a little off but blade closes completely now. Truck started. Later that day (7 hours) truck started. Today truck no start. It's gotta be combo of 54 year old thermosatic coil and worn primary throttle shafts. It takes a long time before the coil will let the idle speed drop. The truck runs great after it starts and starts right up when warm.

[geezer#99]

Describe your cold start procedure.

[BDC90]

Truck in neutral gas pedal to floor, let pedal up and turn key.

[geezer#99]

Pump it twice.
Once might not deliver enough fuel.

Another thing that helps is more timing.
What’s your initial timing set at?

[Wrenchbender Ret]

Pump the gas pedal as you crank it when cold. The accelerator pump pulls off the bottom of the fuel bowl. As soon as the gas gets to the bowl the accel. pump will prime it & it will start. When engine is warm after setting a while hold the gas pedal down while cranking to clear out any flooding from percolation.

George