Choke connections???
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Junior User
Joined: Apr 2004
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From: Newport, North Carolina
Choke connections???
The choke on my 1 bbl yf carb has a vacuum connection and also a electrical connection! How do these work together and are both needed to work properly? The reason that I ask is that the electrical lug to the choke is broke off and impossible to put back on! A little choke theory (electric/vacuum) would be great about now.
Gene
Gene
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
The electrical lead is used to heat up a thermostatic coil inside the choke housing. As current continuously flows through it, the coil gets hotter. Because of thermal expansion and the spring-like design of the bimetallic coil, it sort of "unwinds" and a tab at the end of the coil moves the choke plate open, at about the rate the engine warms up.
However the engine can't run with the choke plate completely shut like it is in the morning after you've loaded the choke but before you start the motor. It needs to be open slightly while the motor is starting, and the choke pull-down does this. Manifold vacuum runs to a pull-down piston and it pulls the choke plate open slightly, while retaining the tension in the choke spring as the choke warms up.
However the engine can't run with the choke plate completely shut like it is in the morning after you've loaded the choke but before you start the motor. It needs to be open slightly while the motor is starting, and the choke pull-down does this. Manifold vacuum runs to a pull-down piston and it pulls the choke plate open slightly, while retaining the tension in the choke spring as the choke warms up.
Senior User
Joined: Dec 2003
Posts: 194
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From: new jersey
hard starting
Hello!
I have an 87 f350 w/ 4180 Holley carb, 0n a 460 eng. the choke is hot air /electric.
This is my problem! when starting the truck the choke plate opens fast causing the truck to stall, it opens in maybe 2-3 seconds. Now if I hole down the choke plate about 1/16" from the top of the airhorn it will stay running, Why is that?
and also can you explain where the vacume hose's connect to on a 4180 holley carburator.
There are two ports at the front of the throttle plate, 1 is small the other is larger. I think the larger port is for the PCV valve?? but I don't know what the smaller one is for?? or do I just plug it?
on the passenger side of the carb there are two ports, 1 is just above the choke, I think the hot air tube connects to it??? Don't know!
and the other is up at the top close to the airhorn, Agian, I think that gets connected to the distributors vacume advance?? not sure?
then where would the EGR valve vacume line connect to? do'es it connect to the front of the egr spacer??? don't
oh! almost forgot! the thermactor system has been removed if thats any help with vacume lines, I have 1 vacume line coming from the intake manifold that was going in a tank down by the passenger side of the fender well, because of the air pump system being removed do I plug that line?
Any help would be greatfuly appriciated.
Thanks
AL
I have an 87 f350 w/ 4180 Holley carb, 0n a 460 eng. the choke is hot air /electric.
This is my problem! when starting the truck the choke plate opens fast causing the truck to stall, it opens in maybe 2-3 seconds. Now if I hole down the choke plate about 1/16" from the top of the airhorn it will stay running, Why is that?
and also can you explain where the vacume hose's connect to on a 4180 holley carburator.
There are two ports at the front of the throttle plate, 1 is small the other is larger. I think the larger port is for the PCV valve?? but I don't know what the smaller one is for?? or do I just plug it?
on the passenger side of the carb there are two ports, 1 is just above the choke, I think the hot air tube connects to it??? Don't know!
and the other is up at the top close to the airhorn, Agian, I think that gets connected to the distributors vacume advance?? not sure?
then where would the EGR valve vacume line connect to? do'es it connect to the front of the egr spacer??? don't
oh! almost forgot! the thermactor system has been removed if thats any help with vacume lines, I have 1 vacume line coming from the intake manifold that was going in a tank down by the passenger side of the fender well, because of the air pump system being removed do I plug that line?
Any help would be greatfuly appriciated.
Thanks
AL
Last edited by gearshift101; Nov 17, 2004 at 11:44 PM. Reason: spelling
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