Q-jet choke problem

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Dec 2, 2005 | 07:22 PM

dennis

Thread Starter

Drifting

Joined: Sep 1999

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Q-jet choke problem

Started tuning the edelbrock q-jet.(new 1901). Want to run it while I send the original out for R&R. Got a decent jet/rod starting point ala Lars tuning. I now have a problem with cold start/choke.

When the choke is on full during a startup, the engine runs dead rich, smoking, running like crap. The choke seems to be functioning properly. Closes with a pump of the pedal, opens slightly after starting, etc.

If I hold the choke flap open, it idles up to 15-1800 running smooth, no smoke. Once warm everything is fine. What did I screw up with the jet/rod change?

BTW, I put the original jet/rod back, but the problem is still there. It also seems I have the idle adjusted in awfully far to get an idle. don't know if that can be related.

Dec 2, 2005 | 07:46 PM

BigBlockk

Drifting

Joined: Sep 2004

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From: North Bend Ohio

The rod from the devoiced choke coil on the manifold should have a kink in it. Bend the rod so that it is a little longer. This will force the choke blade open some more leaning the mixture. GO SLOW!!! Choke mechanisms can be very sensitive. A little can go a long way.

BigBlockk

Later.....

Dec 2, 2005 | 07:52 PM

694speed350

Race Director

Joined: Sep 2005

Posts: 18,640

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From: Farragut,TN

don't think choke should close completely. sounds like it should have a slight opening when full on. check the specifactions on the carb. also there should be a cold idle adjustment.

Dec 3, 2005 | 01:03 AM

BigBlockk

Drifting

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From: North Bend Ohio

The choke should close completely while the engine is cranking then pop open 1/8" to 1/4" at the top of the air horn when it fires.

BigBlockk

Later.....

Last edited by BigBlockk; Dec 3, 2005 at 04:57 PM.

Dec 3, 2005 | 08:56 AM

69monzaredbigblock

Instructor

Joined: Jun 2004

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Had the same issue on my L-36. I'm using an Edelbrock 1901 also. The Edelbrock needs to use a small block style choke coil. It opens in the other direction. I tried to turn the coil around on the BB stock one but the positive stop doesn't end up in the right place. Lars figured this out for me and the choke coil of the small block works perfect. It's easy to check, warm up the engine, shut it off take the top of the air cleaner off and see if spring pressure holds the choke open or closed.
Warren

Last edited by 69monzaredbigblock; Dec 3, 2005 at 09:15 AM.

Dec 3, 2005 | 08:58 AM

kb2fzq

Burning Brakes

Joined: Aug 2005

Posts: 1,126

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From: Hudson Falls, N.Y. 76 Vette Modified L-48

Quote:

Originally Posted by dennis

Obviously, on start you're trying to run the engine with little or no air..if the butterfly doesn't open a 1/8-1/4 inch after the engine starts, adjust the choke rod so you have that gap when cold and you hit the gas once, it may not be textbook adjusted, but it'll run correctly during warm up..there should be a fast idle screw that ups the idle speed during warm up, linked to the choke spring..once warm and a hit of the gas the choke opens and the fast idle screw disengages and the primary idle screw takes over...your primary idle adjustment shouldn't involve fast idle...IMO

Dec 3, 2005 | 09:02 AM

kb2fzq

Burning Brakes

Joined: Aug 2005

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From: Hudson Falls, N.Y. 76 Vette Modified L-48

Also...try this link..
http://neptune.spacebears.com/cars/stories/carb.html

Dec 3, 2005 | 12:33 PM

lars

Tech Contributor

Joined: Aug 1999

Posts: 14,365

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From: At my Bar drinking and wrenching in Lafayette Colorado

You need to adjust your choke pulloff - it should pull the choke open 1/4" upon startup, but you can set it up anywhere you need it to be. Drop me an e-mail for a specific choke setup procedure:
V8FastCars@msn.com
Lars