Small engine question? (20 HP Honda)

[gspren]

  I have a Thermal Arc brand welder/generator that I got over 15 years ago and don't use a lot but during power outages it will power the whole house. If run every week it starts and runs great but if it sets a few weeks the gas runs out of the lines and I need to squirt gas or carb cleaner in the carb a few times until it runs enough to pump the line full. The engine is higher than the tank so there has to be a fuel pump with what I guess is a bad check valve, is the pump more likely to be on the engine or an electric one in the tank? The fuel hose is easy to see so could/should I just cut in a fuel shutoff petcock?

[Gearbox]

I would think it may have a pulse pump. I would be guessing here . they are mostly trouble free .

[Hilltop366]

If it was an electric pump I would think it would come on with the key and fill your gas line, so I vote for a pulse pump (diaphragm pump) too.

[gspren]

The pump seems to pump fine but over a few days the fuel runs back to the tank leaving about 24" of empty fuel line and filter, where would the check valve be located? Would the pump itself work as a check valve?

[Hilltop366]

Yes, they usually work like a chainsaw carb fuel pump, diaphragm moves in and out with crankcase pulse and has check valves or flaps to alternate between sucking fuel and pushing fuel to the carb. On lawn tractors it usually it an inexpensive replacement part.

[luap]

It sounds like the diaphragm in the pulse pump needs replacing. When you manually prime the carb and the engine runs fine you say. What is happening is the increased rpms gives a stronger vacuum/ pulse and it pumps. the check valves are just flaps on the diaphragm which over time has  become less flexible.The vacuum hose could also be suspect. Might be easier to replace just the pump unless you like to see how things work. Is the fuel filter between the tank and the pump or the pump and the carb? These days with related fuel problems if this job was brought to me I would go through the complete fuel system-drain and clean tank, new filter and new fuel lines. Adding a pet cock shut off will not fix your long term sitting problem.

[hedgerow]

We have a lot of small engines around the farm that have the pulse fuel pumps and for the most part they work no problem but on our sprayer tender trailer that a fair amount of folks operate its a different story. The engine is a 20 HP Honda also with remote mount fuel tank. It likes to do the same thing if it sets for a bit. After the help burned out the first starter I replaced the fuel pump and that did help. I never had a problem because if it didn't start right up I would just give it a shot of starting fluid and it would take off. It worked pretty good for a year or so after I replaced the pump then it started acting up again and the help burned up the starter again. This time I took the pulse pump off and installed a low pressure electric fuel pump and have never had a issue since and that has probably been well over five years ago. 

[gspren]

Thanks to all for the wisdom. After this stay at home order is lifted I will probably replace the pump and filter, the filter is between tank and pump, and also add a shut off and a T fitting so I could also use a boat tank during long power outages, I have several boat tanks. I also use only ethanol free gas.

[gspren]

 About 45 minutes after my last post on here our power went out for about 5 hours and I ran the welder/generator for the last 3 of those. I don't need it often but when I do it's really nice to have. I had ran it earlier this week so it started up and ran fine.