400m Carburetor problems.
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Mountain Pass
Joined: May 2012
Posts: 100
Likes: 0
From: South of Butler PA
400m Carburetor problems.
The carburetor on my 78 f250 400m is pushing fuel through the needle valve even after many attempts to stop it. I have rebuilt the carburator from top to bottom many times, and have adjusted the (New) float exactly to spec.
I have "bench" tested the carb by hooking an electric fuel pump that would work with the same engine up to it while it was full and seeing if it would push gas. Which it didn't. I can blow into it as hard as I want and no air passes through. But when I hook it up to the truck with the mechanical fuel pump it pushes gas right through the top of the carburetor. If I take the top off it creates a 6 inch high Geyser.
The truck ran fine until I parked it in 2004. I started having these problems about a year before I decided to un-park it and rebuild the engine. I figured it was just some dirt stuck in the seat and could be solved with a good cleaning and rebuild. It seems my problem is with fuel pressure, but I don't know what could be causing the gas to fly right past the needle when it seems to work just fine until I put it on the truck.
Are the any other reasons that gas is passing through the valve when in theory it should be seating correctly, the float- floats, and the fuel pressure "shouldn't" have changed?
I appreciate anyones help, thanks for your time.
I have "bench" tested the carb by hooking an electric fuel pump that would work with the same engine up to it while it was full and seeing if it would push gas. Which it didn't. I can blow into it as hard as I want and no air passes through. But when I hook it up to the truck with the mechanical fuel pump it pushes gas right through the top of the carburetor. If I take the top off it creates a 6 inch high Geyser.
The truck ran fine until I parked it in 2004. I started having these problems about a year before I decided to un-park it and rebuild the engine. I figured it was just some dirt stuck in the seat and could be solved with a good cleaning and rebuild. It seems my problem is with fuel pressure, but I don't know what could be causing the gas to fly right past the needle when it seems to work just fine until I put it on the truck.
Are the any other reasons that gas is passing through the valve when in theory it should be seating correctly, the float- floats, and the fuel pressure "shouldn't" have changed?
I appreciate anyones help, thanks for your time.
Thread Starter
|
Mountain Pass
Joined: May 2012
Posts: 100
Likes: 0
From: South of Butler PA
For the moment, I am only running the truck out of a clean coffee can. Not the best idea, but it works and shouldn't be sucking dirt through.
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