79 302 carb question
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Senior User
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From: Mt. Clemens Michigan
79 302 carb question
ok my girlfriends 79 f100 is making me feel increadible dumb
. since its gotten colder its been running a little rich and it seems that whoever desinged this 2 barrel had a sense of humor because i cant find the air fuel adjusting screw. 
any help or pictures to help figure this thing out? its driving me nuts that i cant tune this thing cause its fouling out the plugs now pretty bad.
. since its gotten colder its been running a little rich and it seems that whoever desinged this 2 barrel had a sense of humor because i cant find the air fuel adjusting screw. any help or pictures to help figure this thing out? its driving me nuts that i cant tune this thing cause its fouling out the plugs now pretty bad.
Posting Guru
Joined: Feb 2007
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From: Wingo, Ky
Mixture adjusting screws are under the front of the carb on each side. Can be difficult to find if you never adjusted them before. If it started running rich after it got cold its probably a choke related issue.
Cargo Master
Joined: Dec 2006
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From: hinckley ohio
the choke cuts the air down so its going to run rich.Does it run good when its warmed up?Also i had a problem with fouling plugs when I had Champions switched to Autolites and never had an issue again.
Posting Guru
Joined: Feb 2007
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From: Wingo, Ky
In cold weather the choke will not want to open if the electric assist and hot air stove are not in working order. Might just be out of adjusment all together.
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From: Mt. Clemens Michigan
it runs great all the time aside from missing when first started in the cold. if i just hold the idle up for like 5 seconds it stops missing. it runs great but when you rev it up a little it blows black smoke. i held the choke open and hit the gas to see if the choke was the cause and it still blows smoke. its got autolights in it now and they really dont look bad. the worst two were just slightly black. the rest looked pretty good. im pretty sure the choke is working good cause it starts up real easy on cold mornings, tap the gas once and hit the key. i already have a new set of motorcraft plugs and might just put them in anyway to see if it changes anything
Cargo Master
Joined: Dec 2006
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From: hinckley ohio
on the passenger side of the carb is a round black thing its held on by three screws loosen the screws and turn the black thing counter cloak wise abut 1]8 turn or so it will open the choke a little to allow more air in but then the choke may not work as good.There is also a adjustment to raise the idle when the choke is on its like 1/4 screw that you can see from the back of the card down low pass side if you turn the screw clock wise it will increase the idle when choke is on.
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Senior User
Joined: Jun 2009
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From: Mt. Clemens Michigan
well i dont think its the choke because i jammed it open and saw no difference. could it just be either a bad cap and rotor or a weak coil. even with the choke wide open its rich. the cap had little bit of build up on it.
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Laughing Gas
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If it's still running rich after the engine has warmed up, and you've verified the choke is opening all the way, it could be a bad float.
Brass floats can develop a pin hole and take on fuel, while the plastic / foam ones can absorb fuel as they age. When they get heavy with fuel, they can sink like a boat causing the fuel inlet needle and seat to stay open causing a higher than normal fuel level. The higher the fuel level, the easier it is for engine vacuum to draw more of it down inside the engine.
Brass floats can develop a pin hole and take on fuel, while the plastic / foam ones can absorb fuel as they age. When they get heavy with fuel, they can sink like a boat causing the fuel inlet needle and seat to stay open causing a higher than normal fuel level. The higher the fuel level, the easier it is for engine vacuum to draw more of it down inside the engine.
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From: Mt. Clemens Michigan
ill have to take a look at the floats then. i replaced the gaskets and accelerator pump a few months ago and they didnt look bad but that dosen't mean anything. thanks for all the responses guys
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