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Old 03-19-2008, 09:42 PM
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Carburetor Problem

I just picked up a 1977 F-250 with a 460 and a C6 for a smoking deal. The only issue is that the 460 isn't running right. It will fire right up, and seems to idle fine, but once any load is put on it (either by revving it in neutral, or trying to move) it sputters and stalls. If I push it too hard, it will just die. My main suspect is the carb. It's a Motorcraft 4350 4bbl. I'm planning on replacing this setup with an Edelbrock Performer intake manifold and 750 cfm carb, but I don't quite have the money to get that yet, so I would like to get the truck at least running decent for a little while.

Looking at the carb, I noticed that there is a spring poking through the top of the carb on the front left hand side. Does that look normal?


Does anyone see anything, or have any ideas as to what could be my problem? Thank you for the help.
http://www.supermotors.net/vehicles/...ry/18523/63231

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Old 03-19-2008, 10:35 PM
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It's pretty common to blame the carb.

It sounds like a fuel delivery (starvation) problem at first blush.
Mechanical (factory) pump?

Pull the line off, and route it into a 1-qt glass jar.
Pull the coil wire off so that it doesn't start when you have someone else crank it.
Watch the fuel stream as it comes out of the fuel line, and into the glass jar.
It should be a fairly long and strong stream of fuel, delivered in a rythymical fashion, and should begin to fill that jar fairly quickly.

If it just sort of "burbles" out or spurts weakly ... check for a filter between the pump and the end of the fuel line. If you can't blame a dirty filter, it may be time to try a different pump.

If the fuel stream IS good ... is there any crud settling in the bottom of the jar?

Is the fuel filter (at the carb inlet) plugged?

If all of the above prove that you have a good volume of clean fuel available, you may have to remove the top of the carb to check the needle and seat, float, and float adjustment.

Try that for starters and let us know what you find.

That spring that you mentioned look like it controls that outlet that you have plugged ... which I believe is just an atmosheric vent, usually hooked up to a carbon canister down below the battery box, close to the frame. You should have this un-plugged ... and at least hooked up to a hose and filtered.
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Old 03-19-2008, 11:31 PM
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i don't see the accelerater pump lever, did you remove it? if not that would cause your problems.

sam-missle
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Old 03-20-2008, 06:12 AM
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I haven't removed anything on this carb. Where should the accelerator pump lever be? I'll pull off the fuel line tonight and try to see if the pump is working ok. There's a canister on the drivers side inner fender that is unhooked right now. Should I run a line from that to the outlet with the spring is poking through? The canister I'm talking about is in this picture, just to the right of the master cylinder (black round canister).
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Old 03-21-2008, 07:35 PM
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Well, I spent all day trying to figure this out, and I actually ended up worse off than when I started. Now, it won't even start. Here's what I did today:
Replaced Spark Plugs
Replaced Spark Plug Wires
Replaced Cap and Rotor
Replaced Fuel Filter and Rubber Fuel Line
Swapped Ignition Control Modules with one I know works.

After all that, I tried to start it, and not only would it not start, but after I finished cranking it, gas would spray up through the top of the carb. I checked probably 10 times to make sure that the spark plug wires are in the correct order (which they are), and I pulled the #1 plug and checked to make sure that my distributor was in the right spot (which it is). I tried to test for spark by holding the #1 plug against the intake manifold and cranking it to see if I get a good spark, but when I cranked it, the motor fired right up and actually sounded fairly good (with the exception of the #1 cylinder of course). After I shut it off, I re-installed the #1 plug and tried it again, but the same problems happened, and it wouldn't start. Does anyone have any idea what could be happening? Thanks.
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