69 C20 Carb Help

[DreamRyder1963]

A friend and I are trying to revive a '69 C20 that has trade hands a couple within our circle of associates. The truck has sat in a field for over a year at this point. I have gotten spark, but all the truck does is puff smoke through the carb. In my experience, this means that the it is not getting enough fuel through the carb. Am I right in thinking that the carb is the issue here?

[Prescott]

I would double check the ignition. Make sure the plug wires are on with the correct firing order. Then turn to TDC (make sure it's at the top of the compression stroke) and verify that the rotor is pointed to the #1 spark plug wire. Loosen the distributor clamp slightly so you can turn it just a little as you try to start it. Be ready to smother any fires. Then, check to see if you are getting fuel.

[DreamRyder1963]

We already changed out the ignition and set it to tdc on the number 1 wire. The carb is squirting fuel through the accelerator pumps. Despite this all it does is puffs smoke out the carb.

[DreamRyder1963]

I did also notice once I removed the carb that the butterflies only open half way. Is this normal on a quadrajet?

[Wrenchbender Ret]

Sounds like a stuck valve or the timing chain has jumped time. If you are getting gas in the carb & it is pumping into the throat it should run.
Is it the primary throttles that don't open all the way or the secondary, or the air valves?

[DreamRyder1963]

Primary throttles only half way open.

[DreamRyder1963]

This is as far as they will open.

[geezer#99]

You're timed 180 degrees off.
There's binding in your linkage on the carb. With that much opening on the primary the secondaries should be open too!

[jonabalco]

I would just find a good used carb and throw it on and then pull #1 plug and make sure u are on tdc and check your timing to see your lined up then go from there

[Zeke's Garage]

There may be some binding on the carb, but the primaries are nearly fully open. Since the secondaries on a Q-jet are vacuum, they won't be tied to the primary linkage.

But, even with the carb in the shape it's in, you should at least be able to get it to hit and fire with whatever fuel it's getting. How much do you know about the engine? Could it have a bent valve, or jumped time or have all the lobes wiped on the cam?

Have you verified TDC with a pencil in the cylinder, or 'blow your finger off' test? If you're going by the timing mark on the damper you could be off due to outer ring slippage. You really need to verify TDC. Pull the driver's side valve cover off and watch the valves to verify both intake and exhaust are closed on #1.

On an unknown engine, I like to try to verify there's compression, and that I'm getting a decent spark through to the plugs. Then I use some starting fluid right down the carb to see if I can get it to fire and run. From there you can check and verify timing, carb mixture and using a vacuum gauge to get an overall health check on the engine.

Good luck with it.