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#1 |
Registered User
Join Date: Mar 2008
Location: Southern California
Posts: 82
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Hello All,
I have what I hope to be a quick question. My choke on my completely stock 396 works just fine, it simple stays on too long. It is an original 4M Carb (if that helps at all) The fast idle appears good and when it is fully warmed up, it runs very well, it just seems when first fired up in the morning the choke stays on way too long and the truck runs terrible, or until fully warmed up, lots of smoke (black) in the mean time and running way, way too rich. I tried reading the manual on how to adjust the choke, but in all honesty, I did not "GET IT". It is a California truck and, like I said completely stock, even has the smog pump connected. P.S. the truck now has 36K miles on it now. Thanks in advance for any help Rick Last edited by Momboy007; 11-06-2008 at 06:33 PM. |
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#2 |
Senior Member
![]() Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,873
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Re: Choke is staying on too long?
I'm in Southern Calif. too and the first thing I do with any carb'd truck or car is disable the choke. You don't need one. I leave the "fast idle" hooked up for easier warm-up but to start you just need to pump it a few times crank it and work the peddle a bit until it runs on it's own.
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. |
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#3 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: Choke is staying on too long?
Check the choke pull, (the round part with a vacuum hose going to it).
If it is not working then the choke will do what you are experiencing. If the choke pull is good then it will need some adjustment which is done by bending the choke pull link to make it shorter. The chokes can be made to work if you take the time to do the adjustments. I have the stock chock on my 71 K-10 which I use for plowing in the winter and the choke has to work, especially on the mornings when it is below zero. Jim
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1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#4 |
member #16
![]() Join Date: Dec 1999
Location: Yuba City Ca.
Posts: 3,618
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Re: Choke is staying on too long?
I would make sure nothing is dirty and sticking. WD-40 or something similar to lube all moving parts. If that doesn't help you might want to try a new thermostatic spring. They will get weak over the years. Also what Jim said about the choke pulloff sounds like that is more liklier to be the prob.
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john http://67-72chevytrucks.com/vboard/showgroups.php board vendors ![]() http://www.flickr.com/photos/1745471...7602865984234/ Last edited by john; 11-06-2008 at 07:56 PM. |
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#5 |
Registered User
Join Date: Mar 2008
Location: Southern California
Posts: 82
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Re: Choke is staying on too long?
Thanks all,
Here is what I have done so far. 1. Cleaned and lubed all the associated parts with the choke linkage. 2. The choke pull down is working properly, I used a small vacuum source and verified, it does indeed pull all the way in. I think the problem may be in the thermastatic coil, it seems that to function correctly, it would have to be Longer somehow, what I am trying to say is if I try to fully open the choke, the coil and linkage would need to be longer, but all the adjustments I keep reading about say to bend the linkage, which in my mind would make it shorter!!???? Do these coil units go bad? How would you replace one? Thanks all again, Rick |
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#6 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: Choke is staying on too long?
Did you try adjusting the choke pull? If it does not open the choke plate far enough after the engine starts then you will have the loading up problem.
The coil should be good. Work with the choke pull on this problem since the coil closes the choke plate but it does not set the plate gap after the engine starts. The manual instructions say to use a gap setting tool for the gap but I have never seen the tool. My suggestion would be to bend the link a little at a time on the choke pull which shortens the link and increases the gap. To lessen the tension on the coil you will need to go longer on the rod but I don't believe that this is your problem. Jim
__________________
1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#7 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
|
Re: Choke is staying on too long?
To adjust how far the choke plate opening is with the choke pull opening it, bending the linkage is necessary. In the picture that I have posted the linkage to bend on this carburetor is the black one in the middle of the pic (your carb can possibly be different). To open the plate gap, bend the black part toward the rear. Small adjustments can make big changes so bend the linkage a little bit at a time and check the gap.
Jim
__________________
1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#8 |
Registered User
Join Date: Mar 2008
Location: Southern California
Posts: 82
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Re: Choke is staying on too long?
I think that should help lots, is the unloader adjustable? the little vacuum pully thing?
Thanks all again, Rick |
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#9 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: Choke is staying on too long?
The vacuum pull is not adjustable.
Jim
__________________
1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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