302 with Carburetor Problems?
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New User
Joined: May 2013
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From: Athens, GA
302 with Carburetor Problems?
Hello All,
I have a 77 F100 with the 302 and a three speed manual on the column. It has the motorcraft 2150 2V carburetor. The truck idles ok and it will run ok as long as you baby it, but if you step on the throttle like your going to pass a car or whenever it gets to about 60 mph it starts spittering and sputtering. I have replaced all the vacuum lines, spark plugs, fuel filter, air filter, rotor, distributor cap, fuel pump, blown out the fuel lines, replaced the strainer on the pickup tube in the fuel tank, and rebuilt the carburetor and none of this has helped. The engine is not original, it has been replaced. The replacement has the egr removed and blocked off. Granted, I'm no mechanic and I'm learning as I go, so if anyone has any suggestions or can give me some advice as what to check I'd appreciate it. Thanks much.
I have a 77 F100 with the 302 and a three speed manual on the column. It has the motorcraft 2150 2V carburetor. The truck idles ok and it will run ok as long as you baby it, but if you step on the throttle like your going to pass a car or whenever it gets to about 60 mph it starts spittering and sputtering. I have replaced all the vacuum lines, spark plugs, fuel filter, air filter, rotor, distributor cap, fuel pump, blown out the fuel lines, replaced the strainer on the pickup tube in the fuel tank, and rebuilt the carburetor and none of this has helped. The engine is not original, it has been replaced. The replacement has the egr removed and blocked off. Granted, I'm no mechanic and I'm learning as I go, so if anyone has any suggestions or can give me some advice as what to check I'd appreciate it. Thanks much.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Can you describe how the carburetor was rebuilt? Did you take it completely apart, soak it in Chem Dip, spray down, rebuild with a new kit, set the float height, etc? I ask because many times, "rebuilt the carburetor" really means "open the air horn and sprayed it with carburetor cleaner."
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New User
Joined: May 2013
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From: Athens, GA
I bought a rebuild kit from O'Reilly auto parts. Took the carburetor apart, replaced all the parts that I could match with new parts from the kit (gaskets, needle valve, ball and weight, accelerator pump diaphragm, etc., whatever was in the kit). I did not soak it in chem dip, but I cleaned all the parts with Gum-Out carb cleaner, then blew out all the passageways with compressed air. I did not replace the float, but I checked the height from the top of the float to the top of the bowl with the needle valve seated and it was set at 7/16". When I put the carb back on and started the truck it idled rough. After the truck was warmed up good I adjusted the two needle valves and it smoothed out the idle. Like I said, I'm no mechanic and all of this is a guessing game to me. I'm never gonna learn though if I don't try.
Cargo Master
Joined: Apr 2009
Posts: 3,038
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From: South west Idaho
I'm thinking accelerator pump too. Did you replace or put back in the rubber check valve behind the accelerator pump. They are easy to break when you replace them , i'v broken my share of them L.O.L.
P.S okay i see you have fuel now so ignore what i ask.
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P.S okay i see you have fuel now so ignore what i ask.
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Last edited by jim collins; Jul 21, 2013 at 02:03 PM. Reason: added more
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Any idea what year the engine is?
Stock or modified?
The centrificals in the distributor may not be working. You can take off the cap and turn the rotor, should be spring loaded, turn one way and go back when you let go, should have decent resistance, but nothing really strong.
Another possibility is the vacuum advance may be pushing your timing too high.
What is your base timing set at? What is your timing at 2000 RPM?
Stock or modified?
The centrificals in the distributor may not be working. You can take off the cap and turn the rotor, should be spring loaded, turn one way and go back when you let go, should have decent resistance, but nothing really strong.
Another possibility is the vacuum advance may be pushing your timing too high.
What is your base timing set at? What is your timing at 2000 RPM?
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From: Athens, GA
Oldman - Don't know the year and can't tell you what the timing is but you lead me in the right direction. When I was checking in the distributor I found the little "c" clip that holds the arm of the vacuum advance on the peg broken and the arm had slipped off the peg. Unfortunately in all my excitement finding this I had put one of the wires up on the star shaped part of the rotor and forgot to put it back in place, so when I tried to crank the engine it cut the wire in two. Pieced it back together and took it for a ride and it runs a lot better now, but I'm gonna have to replace the distributor or at least the stator or whatever that thing is called. I don't trust my repair job. Man if I had a brain I'd be dangerous. Learn something new every day. Thanks again for the info.
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That shouldn't make it run that horribly unless the timing is low or not advancing to begin with.
Could you turn the rotor my hand? Should go around 10-15 degrees and spring back.
Glad to help, hopefully that was all.
Could you turn the rotor my hand? Should go around 10-15 degrees and spring back.
Glad to help, hopefully that was all.
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