Still fighting with Tecumseh HM100

[mowfixer]

I had an earlier post and I got miss fixed by lapping and adjusting valve clearance.

Now I have another very strange fuel flow problem. This is a generator with a large overhead tank and gravity feed fuel system. When I start it I have a full fuel filter
and as it runs the filter slowly empties until engine stalls as it runs out of fuel. If I let it sit a few minutes I see fuel flow back into filter and it will run again for about 10 minutes until filter empties and it quits.

I have all new 1/4 in fuel lines and filter.
I have checked flow from shutoff valve into a bucket and it seems to flow a steady stream.
I know someone will mention gas cap vent but the same thing happens with cap removed and vent is clear.
I even removed filter and put a pipe in place and it still runs out of fuel and quits after 10 minutes.

It looks like motor is taking fuel faster than it can be replaced from the tank. Almost like its not primed but if I unhook hose from carb I have a steady flow. Carb is new
and I have tried old carb with same results.

Maybe the fuel shutoff is a problem but I see good flow but not certain how quickly it should flow. I blew shutoff out with air and and took it apart and looked for obstructions but could it be still slowing fuel flow? I am lost as to why this is happening. Any Ideas?

Thanks

Mowfixer

[BeeZee]

How about something in the tank itself that is floating around the bottom of the tank. Then when you use the generator , the gas flows out for that 10 minute period, and the thing that is floating on the bottom plugs the outlet before the shut-off valve.

[mowfixer]

How about something in the tank itself that is floating around the bottom of the tank. Then when you use the generator , the gas flows out for that 10 minute period, and the thing that is floating on the bottom plugs the outlet before the shut-off valve.

Good idea and I just checked tank and its clean. I removed shutoff valve and notice that plunger that moves ib to shut fuel off seems to partially block fuel flow even when the valve is all the way open. Its made that way and I never have looked at one to see. Plunger blocks over 1/3 of the fuel flow passage even when open all the way.

Not certain if that would cause the problems or not. Seems old carbs had a vent hole drilled on the side to vent the float bowl but new EPA carbs dont have this. Almost seems like air is in fuel system as when its runnig I can see what looks like air bubbles exiting input to shutoff valve in tank.

[BeeZee]

Have you changed the fuel line from tank to carb?

It's a possibility that the float needle valve might be closed cutting off fuel to the float bowl.

[mowfixer]

I have all new fuel lines and I did read the seats may swell on these third party carbs. Wonder if there are better quality seats available

[bgsengine]

is it absolutely fresh (that you KNOW without a doubt) gas? Reason I ask - fuel octane / quality , you could be seeing vapor lock if temperatures are warm enough with that shut off valve partly blocking fuel flow, air pockets can form that actually block fuel flow.. much more likely to happen with poor quality or low octane fuel (higher octane fuel has lower volatility, does not boil as soon as lower octane stuff) .. and in cold temperatures, I'd also wonder about the presence of moisture in the fuel (especially E-10 , which absorbs water from the air, though you won't see any water IN the gas..) as you may be seeing intermittent icing? Just a couple thoughts..

[Skywatcher]

Hi Mow

What is the micron rating of the filter and what shape is it? Generally speaking if it's purely a gravity feed fuel system, a 75 micron white pancake filter is the best one for the application. The fuel filters with the paper element are designed for a system with a fuel pump and tend to cause too much restriction in a gravity fuel system. Check the fuel volume flow from the end of the fuel line where it connects to the carburetor.

Hold the fuel hose at the same level as the carburetor inlet, turn the fuel valve on and let the fuel flow into a measuring jug. A flow of 100 ml/minute (4 oz/min) is more than adequate for this engine, but anything less than this should be investigated. Is the fuel filter getting warm? I have known fuel filters to get warm enough to boil the fuel in the filter causing a vapor lock. Hope this gives you a couple of ideas to work with,

Sky

[BeeZee]

Skywalker, the OP said;

I even removed filter and put a pipe in place and it still runs out of fuel and quits after 10 minutes.

That would eliminate the fuel filter as being the problem.

[BeeZee]

Mowfixer, could you try something for me.

Start the generator up and let it run until it dies. As soon as it dies, I would like you to clamp off the fuel line as close to the carb as possible. Now, take the float bowl off and see if it does have fuel in it or not. If there is no fuel in it, the problem is from the needle valve back to the tank.

I also would take bgsengine suggestion and make sure that the gas is fresh.

[mowfixer]

I will try measuring flow rate as Sky suggested and will do hose pinch off BeeZee suggestion and check float bowl. I did not know what flow rate to expect so this will help a lot. Will be a day or so before I try as its vey cold in garage with door open.

Thanks

Mowfixer