The Stovebolt Site Forums The Shop Area Engine Shop Very hard to start

Item 1: Fuel pumps can deteriorate over time and adversly affect their pumping ability. They contain a diaphram, spring, check valves, and a mechanical lever. Failure or weakening of any of these components can cause inadequate fuel pressure, fuel flow, or their ability to hold a "prime" (fuel within after the engine is shut down). Fuel pumps are tested using a fuel pump volume and pressure tester to measure both pressure AND volume. Low pressure usually means a weakend spring or diaphram. Low volume is usually a bad inlet or outlet check valve. Either way it means rebuild or replace.
Item 2: The carburator, way too often the carb gets blamed yet innocent. During normal cold starts there are several circuits within the assembly that provide fuel to the bore of the carb. The float circuit, the idle circuit/low speed circuit and the choke circuit.
When starting a single depression of the throttle pedal should close the choke valve,(auto choke)closing of the choke valve allows both the idle and low speed jets to meter fuel to the engine which is a very rich mixture. Make sure the choke sysem (circuit) is working / adjusted properly. The fact that you have to pump the accelerator means that either the carbruator is not getting ample fuel during cranking or the carb is faulty. Pumping of the pedal activates the accelerator pump circuit and injects fuel into the bore of the carburetor, which is not supposed to be needed during starting.
All it takes is small amounts of dirt, slug, varnish or bad gaskets within the carb to restrict fuel flow through the idle/low speed jets.
All that technical crap-o-la aside, Do these first before condeming the carb.
Make sure you have unrestricted full fuel flow from the tank to the inlet of the pump. Test the pump with a tester for correct pressure and flow during cranking.(replace if weak)
Overhaul/Adjust the carb.(or replace if extremely worn).