Troubleshooting Genny. Wont stay running

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wopachop

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Onan 5500 it ran for 10 hours. Engine died we figured out of gas. Added gas and primed with the float drain open. Its pumping gas at a decent rate. 

Hit the starter and it runs for 1 second and dies. 

We added oil. 

Its not throwing a code. Zero red light flashes. 

Maybe its the little solenoid on the carb? Ive read about them failing but havnt dove in deep. Hoping we have the manual to check the troubleshooting guide. 

Removed the air filter and shot brake cleaner. That always worked in the past. Now its not working. Makes me think its spark related. 

Some type of saftey im just not sure yet. Any ideas? It definitely starts. So its getting spark in the beginning. 

 
Added oil. 

One idea is the oil sensor broke or is loose. I think low oil is supposed to throw a code.

 
Stupid question BUT, Did you check the coil wire and put in a new plug?

I had a 300watt genny that acted similar and I had a bad plud. It had a hairline crack in the porcelin.

 
It happened at the end of the trip on SGs trailer. All ive done so far is open the float bowl drain and hit the prime button to confirm the carb is getting fuel. 

Pulled the air filter and tried making it run off brake cleaner. 

Will check the plug wires. I read there are 2 spark plugs and one of them is hard to reach. 

 
wopachop said:
Onan 5500 it ran for 10 hours. Engine died we figured out of gas. Added gas and primed with the float drain open. Its pumping gas at a decent rate. 

Hit the starter and it runs for 1 second and dies. 

We added oil. 

Its not throwing a code. Zero red light flashes. 

Maybe its the little solenoid on the carb? Ive read about them failing but havnt dove in deep. Hoping we have the manual to check the troubleshooting guide. 

Removed the air filter and shot brake cleaner. That always worked in the past. Now its not working. Makes me think its spark related. 

Some type of saftey im just not sure yet. Any ideas? It definitely starts. So its getting spark in the beginning. 
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If it starts up and runs fine when it's cold it prob the fuel pump...there was a batch for a few years apparently that when they get hot they have issues...I was skeptical but had this same issue and it resolved my issues....the gen would always have issues when it was hot outside.

 
wesinls said:
If it starts up and runs fine when it's cold it prob the fuel pump...there was a batch for a few years apparently that when they get hot they have issues...I was skeptical but had this same issue and it resolved my issues....the gen would always have issues when it was hot outside.
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It would run on brake cleaner if it were the fuel pump.

 
Also i believe the float bowl is filling completely because i drained about 3 tablespoons worth into a water bottle. 

Im told the genny sounded a little bit higher pitched than normal. That could be a clue. Not a good clue because that sounds mechanical. Bearing failure or rings scraping? 

Was hoping its an auto shutdown similar to low oil. 

When the genny starts its sounds nornal. There isnt an obvious major parts failure. 

 
Does it backfire when you shutdown? Bad rings low comoression tough start. Valves could need adjusting?

flooded? Pull the plug see if its wet, check for spark while at it

 
Sausage450r said:
Does it backfire when you shutdown? Bad rings low comoression tough start. Valves could need adjusting?

flooded? Pull the plug see if its wet, check for spark while at it
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My son's was doing this. It wouldn't produce enough power to keep running. It would run as long as you held the start button but would stop as soon as you let go. Figured the belt was slipping and not allowing it to produce the power needed to run. Went to change the belt and found the coupling (rubber) had failed also. The flywheel is mounted with a rubber coupling between the belt drive and generator unit.

 
Something weird happened. We topped off the oil in glamis. Drove up to around 3800' elevation. This morning went to check the oil and it was super low. The yellow dipstick was clean and only about 1/4" of oil on the tip. We thought perfect. Hopefully its just the low oil sensor. Put the dipstick back in and now it reads full!!! Almost like a suction developed going from low elevation to high? I briefly looked for what might be a crankcase breather and didnt see anything. Never seen that happen. The trailer is tilted to the drivers side. Which would make the oil level read higher than in the trailer was level.

I just thought. You need to fill the oil super slow because the passage is so small. The oil temp had to be around 40F and really thick. I wonder if we tried cranking the engine. Dispersed the oil. Then didnt wait long enough for the oil level to settle? I could probably go back and watch a camera to see if we checked oil seconds after hitting the starter. 

 
I've been down the genny rabbit hole on mine. New carb, New fuel pump, valve clearance check, new spark plug, oil level check, etc etc 

I came to the conclusion that the new carb, (because of that little solenoid cost just as much), along with seafoam in the cylinder for a couple days, then the oil level has to be just right. Let me go into detail...

Kid on YouTube fixed me right up. Fed seafoam with no spark plug by letting it draw into where the inlet fuel line is at the genny with a glass jar, about half full. Let it sit for 2 days open, no spark plug basically. Then the oil level has to be perfectly a tad low on the "normal" reading of the yellow dipstick, about 20% of the normal range. Not at the top like I do with my cars.  Must check it I think 5 minutes after cranking and gotta be perfect. Voila, that was it. All my genny problems solved. 

I would definitely try the oil level trick first! That was the biggest for me. Good luck! 

 
Oh yeah!! Something about the dipstick being off. Ive read that before. 

Its possible we are now overfilled. 

That wouldnt explain the genny stopping back when it was low to midrange on the dipstick. We added oil in glamis just to scratch that option off. BUt i could totally see someone overfilling and causing a new problem. Could treat it like a performance vehicle and measure out the oil. Do an oil change. New filter. Figure out how much volume it takes to get you at the right spot. Thats what i do with my genny using a ratio rite. I think the volume spec is right there printed on the air filter. 

 
wopachop said:
Oh yeah!! Something about the dipstick being off. Ive read that before. 

Its possible we are now overfilled. 

That wouldnt explain the genny stopping back when it was low to midrange on the dipstick. We added oil in glamis just to scratch that option off. BUt i could totally see someone overfilling and causing a new problem. Could treat it like a performance vehicle and measure out the oil. Do an oil change. New filter. Figure out how much volume it takes to get you at the right spot. Thats what i do with my genny using a ratio rite. I think the volume spec is right there printed on the air filter. 
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Hey now...don't be too hard on yourself!

:lmao:

 
I just went through a similar problem fixing my buddys 4000 onan, It would run great for a hour or two then die , installed a new carb and it did the same, I searched the internet and came across a thread where this guy said that some of these onan motors had the wrong dipstick , I was thinking this is odd, He suggested dumping the oil and put the factory required amount back in it, Well the generator did need a oil change so i dumped the oil and measure it , Sure enough the motor had 22 ounces more than it needed . After putting back the factory required amount , it would just barely show any oil on the dipstick. Ran perfect after that. Go figure to much oil 

 
when you unplug the oil sensor it should run. its a normally closed switch add pressure its a open circuit. no oil pressure shorts to ground and shuts down the engine. the solenoid on the bottom of the carb is a anti dieseling solenoid because of the heavy rotating mass of the armitaure when you shut it off it has to kill spark and fuel otherwize when hot the engine will diesel and make all kinds of noise. the solenoid has a pin on the end that plug the passage for the main jet in the carb when running it pulls the pin out of the jet and allows fuel to flow. i had one go bad and just cut the pin off to get thru the weekend 

 
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if the engine is running too fast or too slow some generators will shut off they need to run a constant rpm 1800 to produce 60 hz if too fast it may be shutting down on over speed. also by pressing the off switch 3 times i should flash your codes.    this fixes alot of problems https://www.amazon.com/dp/B07X1PV5G9/ref=sspa_dk_detail_1?psc=1&pd_rd_i=B07X1PV5G9&pd_rd_w=cKeEk&content-id=amzn1.sym.88097cb9-5064-44ef-891b-abfacbc1c44b&pf_rd_p=88097cb9-5064-44ef-891b-abfacbc1c44b&pf_rd_r=0DZTPGD9MGSW4GAX6F89&pd_rd_wg=HdtLP&pd_rd_r=65cb5cfc-ab43-407f-a936-169239a9b562&s=automotive&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw

 
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My Honda 3k that was completely rebuilt last season ($1200) has been sitting in my enclosed all summer. Fired it up last Fri and but had to use a little starting fluid, ran for 20 mins, no issues, shut it down and headed to Glamis. Put it next to my kids toy hauler and had to use starting fluid again. It ran for 5 mins and shut off, repeated this 3 more times and said eff it, loaded it in my truck. Has oil and fuel, just won't stay running. Taking it to the lawn mower shop that fixed if before. They are in North Hollywood and service all the movie studio generators. Guy usually has 20 in the shop.

 
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