Generator won't run off internal tank

BarnyardEngineering

Well-known Member
Location
Rochester, NY
I live just outside Rochester NY, got hit by the big wind storm, no power. First time I've been without power more than 8 hours in the 11 years I've lived here, and first time I've been without power for more than 4 hours in the winter time.

I have this CaseIH 3500W inverter generator that I use for camping, plenty to run the basics. Always been hard to start, and last summer it developed this habit of running for about 30 minutes, then acting like it's out of fuel and quitting.

When I gravity feed it from my test tank it runs like a Swiss watch under full load for hours and hours.

So, it is a fuel feed problem. I have replaced the fuel pump, the fuel filter, and the lines from the tank to the carburetor. It still won't run off the internal tank for more than about 30 minutes.

The fuel pump is fine. I can suck/blow on the impulse line and it shoots fuel. However, when it is connected to the impulse port on the intake while the engine is running, it barely dribbles any fuel at all. The impulse port on the intake is CLEAR; I took the carb off and ran a wire through it.

Any ideas where on the engine I could get a better impulse for the pump?
 
Looks like you have isolated the issue to fuel delivery from the internal tank via the pulse fuel pump.

First thing I would look at is the internal tank. Is there water in it? Is there rust or some other contaminate in it? Is there a plugged screen? If that all checks out you
likely have a leak on the suction side of the fuel system. IE the fuel line between the pump and the tank. Don't ignore it being the line itself.

hth

jt
 
I have replaced the impulse pumps on our toys with low pressure battery operated pumps. The impulse pumps need a strong vacuum signal to work and often will not work at startup. Of course if you do not have a battery on your generator this will not work for you.
 
I'm not familiar with this unit. I don't know what you mean by internal tank. Have you tried running with the cap loose?

It seems like with vibration, heating, and the vaporizing effect of fuel, gas tanks usually develop pressure, rather than a vacuum. Of all the small engines I have worked on in the past, I had one which would run fine until it developed a vacuum in the tank. Had to open up the vent holes in the cap.
 
The fuel tank was drained and inspected, and the old fuel dumped into an old tractor. The fuel tank is CLEAN inside. No signs of any contamination, dirt, water, rust... Like new.

I tried the fuel cap. When it started sputtering, the first thing I did was open the fuel cap thinking it might be out of gas. It kept sputtering, even after I refilled the tank.
 
How about an answer from way out in left field. Some of those will shut off if they're low on oil. Could it be right on the verge of being low?
 
If you have a shut off at the bottom of the tank check to make sure something isn't
blocking the hole. Don't ask how I found out about that.
 
I think you are losing your impulse. Assuming that it is using crankcase pressure, oil fill plug? Dipstick? Crank seals? Valve cover vent? I would probably try to rig something like a mity vac pump to the crank
case, and after it quits, see if you can pull vacuum on the crankcase.

One other thing I would check if you haven't already is the gas tank vent!
 
Drain the tank and remove the tank fitting or valve if it has one. Check for a very fine mesh screen either in the out let on the tank or on the valve. I have run into several different tanks in the last couple years that the screen was totally clogged. One older briggs had a screen molded into the outlet and had to be flushed in place.
 
You are on the right track. If the fuel tank extends lower than the carb, it must have a pump. if the pump is not working the
valving in the pump may restrict flow unless the tank is high enough to overcome the check valve springs. Jim
 
I wouldn't think that it would start right up and run for hours off the test tank, if the oil sensor was causing it to shut down. It's definitely a fuel supply problem.

The impulse is vacuum off the intake port on the engine block.
 
On some hard to start small engines I have to squirt carburetor cleaner into the intake to get enough fire and impulse signal for the engine to run on its own. They usually run fine once they start. Replacing the diaphragm in the impulse pump helps mine start better. Diaphragms get hard and stiff over time, impulse signals are very weak to begin with.

I don't have a good explanation for quitting after 30 minutes. When it quits try adding more fuel, if that helps the fuel pump could be weak or something in the fuel tank is plugging the outlet.
 
I also have the IH 3500 inverter generator. Mine is also hard starting, poor choke design IMHO, especially after months of non use. I fixed the hard start by drilling a 1/8 inch hole in the carb air intake ,right in line with the carb, so I can feed it propane from the valve and gas tube of a junked brenzomatic propane torch. I start and run it on propane through that little hole until the carb clears out and runs on gasoline. I have never had a problem with the gas feed from the internal tank, possibly a cap vent problem ? Remember the gas cap has a little open / closed twist valve that must be in the open position to run. Also try replacing the fuel pump pulse hose in case it has a problem.
 
My bet is that the tank vent is clogged. Look at the cap and see if there's dirt or mud in the vent hole.
 

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