I have a 72 gmc pickup with a 350engine and a 4brl carb,the problem is that my carb is not getting any fuel but when I remove the fuel line from the carb it's full of fuel,and when it does run as I step on the gas it just bogs out,also while engine is off as I press the throttle I can see a strong stream of fuel coming out the jets.but when running no fuel comes out of the jets at all

I don't know the vehicle, but the carb bowl is not venting.

Could be charcoal canister system, bowl vent etc.

If you loosen the gas cap it may improve. That isn't a permanent fix.

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Originally Posted by KeepItSimpleStupid

I don't know the vehicle, but the carb bowl is not venting.

Could be charcoal canister system, bowl vent etc.

If you loosen the gas cap it may improve. That isn't a permanent fix.

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While the engine is off fuel comes out the jets just fine but while running it won't

It sounds like you need that carb overhauled and cleaned in an ultra-sonic bath to clear the tiny passages that have likely become varnished over time.

When you step on the gas, the accelerator pumps gives a visible squirt of fuel to provide power, but when the engine is running at idle, little fuel is needed and often cannot be seen.

Find a shop that specializes in carburator work and have them check yours. Once finished, you should have plenty of power and performance.