Carburetor/choke Adjustment
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New User
Joined: Jun 2004
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Carburetor/choke Adjustment
I Recently Installed A New Motorcraft Two Barrel Carburetor
On My 78 F100, 400 Eng. Had The Time Checked And Set Today. It
Still Runs Rough. How Do I Check The Choke And Fuel Air Mixture
Setting???? How Do You Adjust The Choke???
On My 78 F100, 400 Eng. Had The Time Checked And Set Today. It
Still Runs Rough. How Do I Check The Choke And Fuel Air Mixture
Setting???? How Do You Adjust The Choke???
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
To adjust the fuel\air mixture, screw the two mixture screws all the way in, then back out 1 and 1\2 turns. Then run the motor like that, and turn them in our out (both screws together) to get a smooth idle.
Set the choke when the motor is cold. Loosen the three retaining screws around the black choke housing on the passenger side of the carb. Rotate it towards the rear of the truck 90 degrees, then towards the front until the choke plate on top starts to open, then rotate it towards the back again. Stop when the little notch on the top of the black housing matches the little correct notch on the metal choke base. To find out which notch to land on look on your engine decal or Chiltons (rich notches are towards the rear, lean notches are towards the front). Then screw the three screws back in. Your choke should be shut with a bit of tension holding it shut.
Set the choke when the motor is cold. Loosen the three retaining screws around the black choke housing on the passenger side of the carb. Rotate it towards the rear of the truck 90 degrees, then towards the front until the choke plate on top starts to open, then rotate it towards the back again. Stop when the little notch on the top of the black housing matches the little correct notch on the metal choke base. To find out which notch to land on look on your engine decal or Chiltons (rich notches are towards the rear, lean notches are towards the front). Then screw the three screws back in. Your choke should be shut with a bit of tension holding it shut.
Postmaster
Joined: Feb 2003
Posts: 4,043
Likes: 4
Remember the idle mixture screws only control the mixture at idle. If your having drivability problems at speed or off idle then it isn't the screws. To adjust the mixture above idle it is metering jets inside the carb.
