pump is new … probability of failure is low but if it was…… the diaphragm would be punctured or leaking.
I would first concentrate on hose and all fuel related fittings….sucking air. check o-rings, claps tye wraps etec…. cracked pick-up tube in the tank (?)
It is not uncommon to see some air in clear fuel lines, near impossible to get it all out. Try pumping the fuel bulb while the engine is idling to see if that makes a difference.
and any air in the fuel would be vented out of the carb via the breather hole . today they call it vapour seperator (VST) because high pressure DI engine don’t like air
Yes hoses can give nightmares. Had an old surgery table that would go up but not down. The hydraulic pressure line was flaking off the inside diameter & hanging up the electric valving. The hose had pieces of hose inside liner hanging up valving, tiny pieces!! That would tear up a carb.
Just my 2 cents for what it’s worth….whenever I planned on converting to a fuel pump and single hose tank, I would always get the motor running well first with the original dual hose tank pressure system. Once I knew it ran fine that way, then I would convert to a fuel pump. Any problems after that were more easily diagnosed.
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