Choke won't close
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5th Wheeling
Joined: Oct 2013
Posts: 46
Likes: 0
Choke won't close
Hi all. I am trying to adjust the choke on my 76 F150. I've got the 390 and Mastercraft carb. The choke doesn't close after pressing the gas pedal. I tried to adjust the choke setting on the side, but it doesn't do anything. I'm carb stupid. Do I have a linkage problem?
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Is this a 2-barrel or 4-barrel? If you loosen the 3 retaining screws and rotate the choke cap toward the back of the truck with the throttle held OPEN, does the choke plate rotate along with the cap?
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5th Wheeling
Joined: Oct 2013
Posts: 46
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2 barrel. I didn't hold the throttle open at the same time. Will that make a difference? I'll try that. Thanks
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5th Wheeling
Joined: Oct 2013
Posts: 46
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Ok. Did that. Butterfly didn't move at all. I turned it all the way back. Nothing. The only way it will move is if I push on the linkage.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Pull off the choke cap, and put it back on, this time making sure the tang at the end of the spring actually engages the linkage. If you are confident that the tang is engaged, and the linkage is not binding (based on the fact that you can freely close the choke plate by hand), then the choke thermostat is worn and must be replaced.
If the linkage is not bound (which you make sure of by opening the throttle), the choke should be able to close with the cap rotated to 3-rich assuming the cap is completely cooled off (several hours). If the engine has recently been ran or the choke has been heated up in any way, none of this is valid. The choke is only to be adjusted if the engine is completely cooled down, as it would be if it sat overnight.
Once it's cooled down, the fast idle linkage prevents the choke cap from closing, hence having to keep the throttle open when rotating the cap. This is the same reason you must pump the pedal once when cold-starting a carbureted engine.
If the linkage is not bound (which you make sure of by opening the throttle), the choke should be able to close with the cap rotated to 3-rich assuming the cap is completely cooled off (several hours). If the engine has recently been ran or the choke has been heated up in any way, none of this is valid. The choke is only to be adjusted if the engine is completely cooled down, as it would be if it sat overnight.
Once it's cooled down, the fast idle linkage prevents the choke cap from closing, hence having to keep the throttle open when rotating the cap. This is the same reason you must pump the pedal once when cold-starting a carbureted engine.
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
You use it only when you need it, and you know when it's open or closed.
Post Fiend
Joined: Sep 2006
Posts: 14,325
Likes: 14
From: Island Southeast Alaska
It keeps kids from taking my rig cuz they can't figure out how to
start it. But with the dimmer switch on the floor they can't figure
that out either.
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Post Fiend
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Post Fiend
Joined: Sep 2006
Posts: 14,325
Likes: 14
From: Island Southeast Alaska
I've been teaching the proper use of it to my boys. But at 12 and 14 they are
taking a while to get the hang of pushing it in a little when it starts so it runs
smooth on fast idle while warming up.
taking a while to get the hang of pushing it in a little when it starts so it runs
smooth on fast idle while warming up.
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
Though a manual choke probably would stymie most kids that have never seen one.
Post Fiend
Joined: Sep 2006
Posts: 14,325
Likes: 14
From: Island Southeast Alaska
Not so much thieves as neighbors and friends borrowing it without askin.
Nobody ever takes the keys out around here. If ya do ya never find them
again.
I have like 4 jugs of gas for the ATV's on the deck. They was always empty.
Than I wrote on them that one had sugar in it, You guess which one. That helped
a lot. No not thieves, just so called friends helpin them self's to Papas stuff.
You see we live in a very remote village. Like an hour and a half to the store
on a good day. So in an emergency like a kid getting hurt we don't ask, we just
use what we need than replace it. This as it should be.
Nobody ever takes the keys out around here. If ya do ya never find them
again.
I have like 4 jugs of gas for the ATV's on the deck. They was always empty.
Than I wrote on them that one had sugar in it, You guess which one. That helped
a lot. No not thieves, just so called friends helpin them self's to Papas stuff.
You see we live in a very remote village. Like an hour and a half to the store
on a good day. So in an emergency like a kid getting hurt we don't ask, we just
use what we need than replace it. This as it should be.
Senior User
Joined: Apr 2012
Posts: 335
Likes: 0
From: San Diego, CA
Not so much thieves as neighbors and friends borrowing it without askin.
Nobody ever takes the keys out around here. If ya do ya never find them
again.
I have like 4 jugs of gas for the ATV's on the deck. They was always empty.
Than I wrote on them that one had sugar in it, You guess which one. That helped
a lot. No not thieves, just so called friends helpin them self's to Papas stuff.
You see we live in a very remote village. Like an hour and a half to the store
on a good day. So in an emergency like a kid getting hurt we don't ask, we just
use what we need than replace it. This as it should be.
Nobody ever takes the keys out around here. If ya do ya never find them
again.
I have like 4 jugs of gas for the ATV's on the deck. They was always empty.
Than I wrote on them that one had sugar in it, You guess which one. That helped
a lot. No not thieves, just so called friends helpin them self's to Papas stuff.
You see we live in a very remote village. Like an hour and a half to the store
on a good day. So in an emergency like a kid getting hurt we don't ask, we just
use what we need than replace it. This as it should be.
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