I have having issues getting my 83 bronco with I6 300 to start. It cranks away with out firing. If I dump gas into the carb and rev it few times it runs just fine and will start right back up. The bronco sat for about 10 years, was running okay when put into storage but to get started now I have to dump gas in carb. I have replaced fuel pump, fuel filter, spark plugs, cap and rotor. It does have an Clifford manifold, headers and holly 4 barrel carb on it. I rebuilt carb on it as well. What am I missing? How can I test the vacuum when it isn't starting? Thanks

 

It sounds like the accelerator pump is not working. With the air cleaner off and engine not running, look down the throats of the carburetor and open the throttle with your hand. You should see two streams of gasoline.

 

Essentially you are getting no gas at start-up - as 1986F150six said, it could be your accelerator pump. Or it may not have any gas to pump - make sure your float bowl isn't drying out for some reason. Leaking out, etc... could have a slow leak at your gas line, maybe - wipe it with tissue paper and see if you have any damp spots. Especially since you recently reassembled it.