For an old vehicle with questionable fuel tank and fuel pump.
I use a one gallon pump up weed sprayer.
Make sure the gas tank is disconnected from the fuel pump and then clamp in the pump sprayer directly to the carb.
Do Not Pump the sprayer very much!
It may blow gas past the needle valve, flood the engine and leak gas out on the exhaust manifold.
Also have a heavy rag and fire extinguisher, just in case something does not go as planned.
Don
