Home » Public Forums » GMCnet » Automatic choke
| Automatic choke [message #288273] |
Tue, 06 October 2015 13:19  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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If someone knows - what temp should I see on the choke stove or the spring housing itself when the engine is up to temperature. I'm setting the choke, and I'm not finding the sweet spot. I've a manual one I could put in, but I rather it behaved as it should. It's currently i tick forward of center on the dial.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Automatic choke [message #288277 is a reply to message #288273] |
Tue, 06 October 2015 13:57  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Johnny, Engine stone cold after sitting overnight. Open hatch, remove
aircleaner. DO NOT TURN ON THE IGNITION SWITCH. By hand, lightly pull back
and release on the throttle cable while observing the choke plate. It
should snap closed. Take your finger and press lightly on the choke plate.
If it is tightly closed, loosen the 3 screws that hold the coil housing and
rotate the housing until the choke plate opens part way, then turn it back
while watching the choke plate. When it JUST REACHES the closed position,
tighten the 3 screws. Then, and only then, turn on the ignition and watch
the choke plate. If your electrical connections are good, within 15 to 20
seconds you should see it move. If not, check voltage and grounds. If all
else fails, replace the coil on the choke. They don't last forever. If you
do this on a slightly warm engine, all bets are off.
Jim Hupy
Salem, Or
78 GMC ROYALE 403.
On Oct 6, 2015 11:19 AM, "Johnny Bridges" wrote:
> If someone knows - what temp should I see on the choke stove or the spring
> housing itself when the engine is up to temperature. I'm setting the
> choke, and I'm not finding the sweet spot. I've a manual one I could put
> in, but I rather it behaved as it should. It's currently i tick forward of
> center on the dial.
>
> --johnny
> --
> '76 23' transmode Norris upfit
> Braselton, Ga.
>
> "Sometimes I wonder what tomorrow's gonna bring when I think about my
> dirty life and times" --Warren Zevon
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] Automatic choke [message #288281 is a reply to message #288277] |
Tue, 06 October 2015 15:29 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Uh, Jim, this'n's stock. I can set the electric ones, but on the stove style I sometimes get crossed up. I've got it closing properly, much to the relief of the starter - but I'm not sure it's getting all the way open. I may not have run the engine long enough to get the stove fully up to temperature.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Automatic choke [message #288283 is a reply to message #288281] |
Tue, 06 October 2015 15:51 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Johnny, same process as the electric one. Except, you have to wait for
enough heat to form in the stove. If you have blocked exhaust crossovers,
it will take longer than the electric one to open. Another thing I forgot
to mention is to make sure that the vacuum dashpot that opens the choke is
working. They leak vacuum when they fail and don't open the plate. Also
check that the correct vacuum port on the carb is hooked onto it. Because
of the slower opening of the manifold heated choke, I sometimes set them a
bit lighter so they open sooner. In the south it works ok. Not so much in
Michigan winters.
Jim Hupy
On Oct 6, 2015 1:30 PM, "Johnny Bridges" wrote:
> Uh, Jim, this'n's stock. I can set the electric ones, but on the stove
> style I sometimes get crossed up. I've got it closing properly, much to the
> relief of the starter - but I'm not sure it's getting all the way open. I
> may not have run the engine long enough to get the stove fully up to
> temperature.
>
> --johnny
> --
> '76 23' transmode Norris upfit
> Braselton, Ga.
>
> "Sometimes I wonder what tomorrow's gonna bring when I think about my
> dirty life and times" --Warren Zevon
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: Automatic choke [message #288291 is a reply to message #288273] |
Tue, 06 October 2015 18:00 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Well, I think it's at least close. I have to run it up and get gas tomorrow, that will get itcompletely warm, I'll see if it's open then. The pull off is working.
Thanks!
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Automatic choke [message #288312 is a reply to message #288273] |
Wed, 07 October 2015 07:31 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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The bimetallic spring setting is a bit forgiving, but the pull-off setting is extremely critical and touchy and what definines how well it runs durring warm up. There are specs in the books on how much the pull-off cracks the plate open at start up, or you can start cold and observe how it opens and at that point a couple seconds after starting see if you can slightly open or slightly close by hand to see which way runs better. When in doubt I error towards the lean side, to prevent loading, fouling the oil, and keeping emissions as low as possible. That very short vac hose on the pull-off can be cracked and look ok at first glance. AFAIK the RP pull-offs are gone but there are Chinese all bright white plastic ones if the diaphragm is shot on yours. But if working as you say it probably only needs a slight adjustment. Also, you want the bimetallic set to open fully so the secondary air valve lockout is released.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Automatic choke [message #288315 is a reply to message #288312] |
Wed, 07 October 2015 08:45 |
Dan
Messages: 99
Registered: August 2014
Location: Allentown, NJ
Karma: 0
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JohnL455 wrote on Wed, 07 October 2015 07:31The bimetallic spring setting is a bit forgiving, but the pull-off setting is extremely critical and touchy and what definines how well it runs durring warm up. There are specs in the books on how much the pull-off cracks the plate open at start up, or you can start cold and observe how it opens and at that point a couple seconds after starting see if you can slightly open or slightly close by hand to see which way runs better. When in doubt I error towards the lean side, to prevent loading, fouling the oil, and keeping emissions as low as possible. That very short vac hose on the pull-off can be cracked and look ok at first glance. AFAIK the RP pull-offs are gone but there are Chinese all bright white plastic ones if the diaphragm is shot on yours. But if working as you say it probably only needs a slight adjustment. Also, you want the bimetallic set to open fully so the secondary air valve lockout is released.
For what its worth I spent weeks adjusting my choke, installed a new electric choke and still could not get the engine to start and warm up in a reliable manner. Then I spent 5 minutes adjusting the choke pull off and everything has been fine since.
Dan DeLuca
1978 Eleganza II (http://imgur.com/gallery/YFHhK)
Parked at Evil Monkey Farm in
Allentown, New Jersey
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| Re: Automatic choke [message #288321 is a reply to message #288273] |
Wed, 07 October 2015 12:35 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Yep. A couple degrees of choke plate angle makes all the difference between too rich and too lean.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Automatic choke [message #288322 is a reply to message #288273] |
Wed, 07 October 2015 13:36 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Well, I set it cold by spec..snap shut, back off, bring it up to just touch the air horn. Starts great, couple pumps and two or three seconds of spin and vroooom. But. Even at run temp as indicated by the DigiPanel and the dash gauge, and with the bimetal bar touching the stop, several hundred degrees on the manifold stove, nearly 200 on the outlet pipe from the bimetal, the secondary latch isn't released, and the choke plate isn't vertical. There's enough slop in the linkage for it to swing vertical easily, and when it does, the lock pawl disengages. The vacuum unloader looks to be operating correctly, and I haven't messed with it atall. I'm wondering, does the choke plate pull vertical when there's more air flow? I'm observing all this at idle and high idle, I purely hate to wind up an unloaded engine. I'll give it a go in the morning up the highway and see how it does. Failing that, we may have the Canadian World Tour in our future. It's probably due for a build.
I wonder if one could find a manifold which was low enough to fit, and would accept an AFB. Those I can make work 
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
[Updated on: Wed, 07 October 2015 13:38] Report message to a moderator |
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| Re: Automatic choke [message #288327 is a reply to message #288322] |
Wed, 07 October 2015 16:43 |
Adrien G.
Messages: 474
Registered: May 2008
Location: Burns Flat, OK 73624
Karma: 1
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Johnny Bridges wrote on Wed, 07 October 2015 13:36Well, I set it cold by spec..snap shut, back off, bring it up to just touch the air horn. Starts great, couple pumps and two or three seconds of spin and vroooom. But. Even at run temp as indicated by the DigiPanel and the dash gauge, and with the bimetal bar touching the stop, several hundred degrees on the manifold stove, nearly 200 on the outlet pipe from the bimetal, the secondary latch isn't released, and the choke plate isn't vertical. There's enough slop in the linkage for it to swing vertical easily, and when it does, the lock pawl disengages. The vacuum unloader looks to be operating correctly, and I haven't messed with it atall. I'm wondering, does the choke plate pull vertical when there's more air flow? I'm observing all this at idle and high idle, I purely hate to wind up an unloaded engine. I'll give it a go in the morning up the highway and see how it does. Failing that, we may have the Canadian World Tour in our future. It's probably due for a build.
I wonder if one could find a manifold which was low enough to fit, and would accept an AFB. Those I can make work
--johnny
Get yourself an electric choke thermostat (Airtex #2C1044 76/78 Cad.).
Connect a 16g wire with a 10 amp fuse to the Alt post of the isollator.
Block off stove pipe.
Choke will only operate when engine is running and alt has output.
Works for me.
Adrien & Jenny Genesoto
75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild
Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6
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| Re: Automatic choke [message #288339 is a reply to message #288273] |
Wed, 07 October 2015 20:24 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Well, the spring is going all the way to the stop when it's hot, the stove ain't the problem. If the back barrels will open on the highway, there is no problem. If they won't, either the linkage or the pulloff want fiddling with. I suspect air loading will pull the plate vertical and it will work properly at speed. We'll see.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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