Possibly needs a diaphragm in the carb. Might have clogged fuel pick-up tube. Might have an air leak, typically found at the carb-to-engine interface (mounting bolts loose, bad gasket).

Is that diaphram under the carb where it mounts on the gas tank ? Can I remove the carb without taking the gas tamk off ?

Post the engine Brand, Model, Type etc. so we can try to identify it!
It sounds like a Briggs, but you gave us absolutely no info.

'Carb sits on top of gas tank'
Has to be a Pulsa-Jet.
It's been a long time since I put a diaphragm in, but IIRC the carb and intake runner are screwed to the cylinder and gas tank, so you take it loose at both places to remove. It might not be the diaphragm because the usual symptom is no start. I would take the carb off anyway, put in a new diaphragm and check for contamination in the tank, plugged pickup tubes, etc.

I haven't had a chance to do anything with it yet,maybe this weekend.I'll let you know one way or the other.thanks

I took the gas tank and carb off and cleaned everything good with choke cleaner,including the tank.Put everything back together and it runs great. Thanks Guys