Messing with a buddys 66 F100 with a 352 2bbl motorcraft 2100. Problem was he was leaking gas from the umbrella valve body, my guess was gasket, so I pulled the carb, bought a rebuild kit and replaced the diaphram/gasket. Fixed my leak, but now the truck wont start and is backfiring through the carb. Any ideas? Thanks

 

Is that all that was done to the engine/carb? Completely rebuilt, using all the new parts, plus a full cleaning, or only replace the diaphram?

 

I changed the power valve, the gaskets on the power valve housing, the umbrella valve, and the top bowl gasket. Figured since I had to buy the kit, might as well replace a few other things.

 

my first thought is that backfiring through the carb sounds like timing.
nothing got changed but the carb?

if so- my bet is that your power valve is leaking...a LOT.
had this happen once- if i remember correctly (ha), i had used the wrong gasket between the valve and the carb body.

finally figured it out. pulled the carb, put it up on blocks in a metal tray, and poured gas into the bowl...and watched it pour straight through into the metal pan.