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Engine Randomly Stalls

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bartonkj
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2023/09/03 14:42:30 (permalink)
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Engine Randomly Stalls

Summary:
Why is my generator randomly stalling? And what can I do to fix it?
 
After it stalls, sometimes it comes to a dead stop and needs to be restarted, and sometimes it kicks into life again before coming to a dead stop (i.e., it does not need to be restarted).

Oil level is where it should be and it is on level ground
Gas cap vents properly
Replaced carb
On-Off switch appears to be in solid working order with no visible signs of damage or corrosion
Replaced fuel shutoff valve and  hose from tank to carb, no debris in tank

Details:
15-20 year old Troy-Bilt Portable Generator Model 01919
5550 Running Watts / 8550 Starting Watts
Briggs & Stratton 10 HP Engine Model 204412-0147-E1
This engine comes with either Walbro or Nikki carburetor: mine came with the Nikki (no solenoid)

Has run great for years until latest power outage. Ran great at first, then I shut it off for several hours (because we left home). I did not close the fuel shut off valve. When I tried to start it again, the cylinder was filled with gas and there was lots of gas in the crankcase. I assume the float got stuck open from being gunked up and the gas continued to flow into the engine. I emptied the crankcase and the cylinder, refilled crankcase with appropriate amount of oil, and got it running again.

THEN it started randomly cutting out. The engine runs for some time then randomly dies. Sometimes it catches before completely stopping and sometimes it catches and dies completely. When cold, it seems to run about 15-20 minutes before the first cut out. After first stall it seems to happen more frequently, but at random intervals. When I have to manually restart, it initially started back up easily.

I assumed the carb was gunked up and there was not enough gas flowing continuously. Since you can get replacement carbs for about the same as (or less than) a rebuild kit, I opted to replace the carb with a cheap carb off Amazon.

Started on new carb and still randomly stalls (also - this carb seems to run a little richer than original carb, but carb doesn't have any adjustment screws [neither did the original Nikki, btw]). Then I figured maybe there was a problem with fuel delivery, so I also replaced the fuel shut off valve and made sure there was no debris in the tank (I checked vent on gas cap before getting new carb).

I'm no expert, but I'm also not a total idiot, and I'm stumped.
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    SRTsFZ6
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    Re: Engine Randomly Stalls 2023/09/03 17:11:17 (permalink)
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    Sounds like 2 issues...
     
    The Nikki carb is known for leaking due to it's design.  The internals have a separate internal assembly with the float bowl sandwiching it.  There's a very small o-ring that fails at that assembly (see pic).  That will cause the carb to leak internally.
     
    As for the cutting out, there's usually an "oil level switch" either on the front of the engine or wired to the insides..  That switch does go bad, even thou you have enough oil in the engine..   You can simply un-plug it and just check the oil when you fill up, or replace the switch(depending on your engine).  They'll be a smallish square box where the wire goes up to and a single wire plug.  Just un-plug it..
     
    If you can, get the Walbro carb (OEM).  It's a standard design and IMO, superior to the NIKKI. 
     
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    SRTsFZ6
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    Re: Engine Randomly Stalls 2023/09/03 17:13:31 (permalink)
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    There's a low oil cut off switch, with one wire usually attached to the ft of the crankcase.
     
    They do go bad.  Simply un-plug and it won't kill the ignition.  Of course it won't work so check the oil when filling up with fuel..
     
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    bartonkj
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    Re: Engine Randomly Stalls 2023/09/05 10:17:58 (permalink)
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    It turns out the oil level sensor was the problem. I didn't think to try unplugging it, as I thought they would either work 100% or fail 100%. I didn't realize they could fail intermittently, let alone fail, stall the engine, then recover quickly enough to fire up the engine again before it stopped turning over. But, when I decided to give it a try after multiple suggestions to do so, I unplugged the sensor and it ran 100% for the hour I sat testing it. I did end up cleaning the original carb and put it back on (before the hour long test), as it had a better air/fuel mix than the replacement carb. I also ended up putting the original fuel hose back on between the tank and the carb, as it was prebent to the right shape and the replacement hose got kinked because it wasn't prebent.
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    SRTsFZ6
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    Re: Engine Randomly Stalls 2023/09/05 11:08:27 (permalink)
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    Glad you tried it and got it fixed..
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