choke making me nuts

[jozw30]

72 Olds W30.  pretty stock.  Recent carb re-build (by a pro). Has run fine since I got it.

Couple of weeks ago, I adjusted the timing because I thought I noticed some pinging and I was fairly aggressive with the advance to begin with.  Drove the car afterward and it ran great.

Car sat for about a week and the next time I try to start it, it fires but I can't get an idle at all.  It chugs and pukes like it's immediately flooded. 

The choke is closed, opens partially with the vacuum pull-off, & I see the thermostatic spring opening as it warns up.

I have to wait until the engine is completely warmed up before I can do anything.  If I stab the throttle, it will stall when it comes back down.

Once the thing is warmed up (2-3 minutes), it runs great!

I'm getting pretty frustrated.........

Joe

[Cliff Ruggles]

The choke open angle on cold starts needs to be adjusted.  The choke pull-off opens the choke flap on initial cold starts to the proper angle to keep the engine from flooding out, or being to lean and stalling out.

On that particular model, they used a metal canister that has been discontinued for some time.  We had them reproduced and have plenty in stock.

Some builders use the plastic pull-off from the divorced choke carburetors as a replacment.  This does NOT work well as the arm is too short, requiring bending of the choke related parts excessively to get the choke to open correctly on cold starts.

Anyhow, another problem is that the pull-offs get a small hole in the diaphram, and don't unload the choke correctly.

Those models require bending of the associated parts to get the angle of the choke flap correct.  Not a very sophisticated deal, but it works perfectly once you find the correct setting(s)......Cliff

[jozw30]

Cliff,

Thanks for the reply.  After three days of trying to diagnose the choke circuit (which I was pretty sure was functioning properly), I decided that the only other thing I had changed prior to the problem was the initial timing.  since I didn't have any other bright ideas and the the engine was too hot by then to mess with the choke, I bumped the timing a few degrees and reset the idles.

Today it pretty much fired right up and idled pretty good.  The choke spring opened little too fast, but the car never stalled.  I will add a little tension at a time until I get it where it needs to be.

This was very frustrating, I learned a lot..........

[Cliff Ruggles]

Adjusting the choke only controls how long it takes to fully open.  The initial opening of the choke flap is controlled by the choke pull-off.  On that particular model it involves bending the linkages, but othewise isn't all that difficult.....Cliff