Carburetor Problems?
Laughing Gas
Joined: Jun 2016
Posts: 855
Likes: 56
From: Des Moines, Washington
I don't see any obvious problems with hoses and fittings but did have another thought.
Did you remove the distributor or change the plug wires?
Re-check the firing order, google yourself a picture of a 351W firing order and make sure your #1 wire is on the correct post on the cap. Some caps are marked with a 1. From the pics I found, it should be at the back and on the drivers side.
It is possible to get an engine to run with 2 plugs mis-wired and sometimes even with the cap one hole off but it won't idle and needs a heavy foot to keep it running. It may also backfire or go "phutt" every now and then.
Michael
1974 F250 Super Cab
Did you remove the distributor or change the plug wires?
Re-check the firing order, google yourself a picture of a 351W firing order and make sure your #1 wire is on the correct post on the cap. Some caps are marked with a 1. From the pics I found, it should be at the back and on the drivers side.
It is possible to get an engine to run with 2 plugs mis-wired and sometimes even with the cap one hole off but it won't idle and needs a heavy foot to keep it running. It may also backfire or go "phutt" every now and then.
Michael
1974 F250 Super Cab
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Glad to see you taking on a project like this - I had a '78 w/302 for my first truck when I was a teenager. Great experiences working on it.
Idle screw adjustment made no difference...well I think it's the carb but the next cheapest thing to rule out is the vacuum (BigCountry1978's vacuum check).
If carb you might be looking at a rebuild. only other thing I can think of is bad gas (since that didn't come with the "new" engine). Could run some from a gas can to see if any different.
When it's running (with your foot on the gas), whats the lowest RPM you can hold it to before it dies?
Idle screw adjustment made no difference...well I think it's the carb but the next cheapest thing to rule out is the vacuum (BigCountry1978's vacuum check).
If carb you might be looking at a rebuild. only other thing I can think of is bad gas (since that didn't come with the "new" engine). Could run some from a gas can to see if any different.
When it's running (with your foot on the gas), whats the lowest RPM you can hold it to before it dies?
The carb on it now is the one that came with it and it had a leak but it did run with that carb on it so
I bought another carb that came off a cj7 it was a motorcraft also I put it on and it ran fine and it idled then it started acting up having a surging idle so to fix that and took the part off that one and put it on the carb that came with the truck
Now it don't leak and I can't get the truck to idle
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http://http://youtu.be/32hcZamhy9E
http://youtu.be/32hcZamhy9E
I don't see any obvious problems with hoses and fittings but did have another thought.
Did you remove the distributor or change the plug wires?
Re-check the firing order, google yourself a picture of a 351W firing order and make sure your #1 wire is on the correct post on the cap. Some caps are marked with a 1. From the pics I found, it should be at the back and on the drivers side.
It is possible to get an engine to run with 2 plugs mis-wired and sometimes even with the cap one hole off but it won't idle and needs a heavy foot to keep it running. It may also backfire or go "phutt" every now and then.
Michael
1974 F250 Super Cab
Did you remove the distributor or change the plug wires?
Re-check the firing order, google yourself a picture of a 351W firing order and make sure your #1 wire is on the correct post on the cap. Some caps are marked with a 1. From the pics I found, it should be at the back and on the drivers side.
It is possible to get an engine to run with 2 plugs mis-wired and sometimes even with the cap one hole off but it won't idle and needs a heavy foot to keep it running. It may also backfire or go "phutt" every now and then.
Michael
1974 F250 Super Cab
http://youtu.be/32hcZamhy9E
Laughing Gas
Joined: Jun 2016
Posts: 855
Likes: 56
From: Des Moines, Washington
That answers the firing order question!
I'm not sure which part you swapped from the CJ7 to the original but if it was the lower half and the CJ was not a similar sized V8, you probably have the wrong size jets.
I was leaning toward plugged jets or passages but now wonder if there were differences in the 2 carbs that are causing a way lean mixture due to either jet size or due to a difference in castings.
Michael
1974 F250 Super Cab
I'm not sure which part you swapped from the CJ7 to the original but if it was the lower half and the CJ was not a similar sized V8, you probably have the wrong size jets.
I was leaning toward plugged jets or passages but now wonder if there were differences in the 2 carbs that are causing a way lean mixture due to either jet size or due to a difference in castings.
Michael
1974 F250 Super Cab
Laughing Gas
Joined: Jun 2016
Posts: 855
Likes: 56
From: Des Moines, Washington
Youtube say video is private. And first link has one too many HTTPs
Michael
1974 F250 Super Cab
Laughing Gas
Joined: Jun 2016
Posts: 855
Likes: 56
From: Des Moines, Washington
That's the accelerator pump. It shouldn't make a difference which carb it cam off as long as the linkage is hooked up the same as it came off.
When you pump the pedal, you move the lever on the pump which causes it to send gas straight down the venturis. If you look straight down the carb while working the throttle linkage, you can see it squirt out a little tube, either in the center or on one side of the venturi. When you hit the key, the engine is running on the vapors in the carb.
I'm having a hard time finding a video that shows clearly how to set the mixture screws. This one from
is for the Edelbrock that's on my truck but it gives the first 3 minutes will work on any carb.
You may want to start from scratch with the mixture screws.
Run them in gently so you don't damage the seat then back them out from 1 1/2 to 2 turns. Back the idle speed screw off until the throttle plates are fully closed then run it in until they just start to open. Hold the choke plate closed, open then close the throttle then let go of the choke. Without touching anything, look to see if the idel speed screw is no longer touching the stop. It shouldn't be as the fast idle screw should now be holding the throttle open a bit farther. This is due to the engine needing more air and fuel when cold. I can't tell you how far open it should be, that needs to be set when it's warmed up.
If things are OK with your carb, it should now start although it might be warm enough that you don't need full choke. Even when it's 70° out, I need some choke to get my truck started. Since I have a manual chock, I pull it out till I fell resistance then pull just a bit more. On really cold days, it's out to the stop.
Michael
1974 F250 Super Cab
When you pump the pedal, you move the lever on the pump which causes it to send gas straight down the venturis. If you look straight down the carb while working the throttle linkage, you can see it squirt out a little tube, either in the center or on one side of the venturi. When you hit the key, the engine is running on the vapors in the carb.
I'm having a hard time finding a video that shows clearly how to set the mixture screws. This one from
You may want to start from scratch with the mixture screws.
Run them in gently so you don't damage the seat then back them out from 1 1/2 to 2 turns. Back the idle speed screw off until the throttle plates are fully closed then run it in until they just start to open. Hold the choke plate closed, open then close the throttle then let go of the choke. Without touching anything, look to see if the idel speed screw is no longer touching the stop. It shouldn't be as the fast idle screw should now be holding the throttle open a bit farther. This is due to the engine needing more air and fuel when cold. I can't tell you how far open it should be, that needs to be set when it's warmed up.
If things are OK with your carb, it should now start although it might be warm enough that you don't need full choke. Even when it's 70° out, I need some choke to get my truck started. Since I have a manual chock, I pull it out till I fell resistance then pull just a bit more. On really cold days, it's out to the stop.
Michael
1974 F250 Super Cab
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