Onan 4000 won't stay running

[Mel]

I have an Onan 4000 in my '07 Toyhauler in Vegas. I have done the maintenance myself the last 2 year I've owned it. This includes swapping the carb and fuel pump, oil changes and tune ups. It does not get heavy use but the fuel in the tank is fresh.
The problem I am experiencing is the genie will not stay running. When it is cold it will run perfect smooth for 3 minutes and dies, indicator light blinks 3x (requires service). If I continue to start it again it will only run about 20 seconds before dying. It does this when hooked to shore power or on battery power.
I have done the following to no avail: lowered the oil level to the bottom 1/4 of the dipstick (common issue with Onan is overfilled oil), put Sea Foam into a new gallon of gas and ran it through the fuel line, let it sit in carb 30 minutes then started genie. Neither of these brought any change to the issue.
I have been unemployed for 9 months and am trying to do everything possible before calling out the $100+/hour mechanic to fix this issue. Anyone have a fix? Have I missed anything I could possibly troubleshoot myself? Thanks for any advice, I appreciate any and all suggestions!! Merry Christmas!

 

[Kevin D Pem]

Sounds to me like you are running out of gas.

Possible problems:
Below 1/4 tank of gas.
Filter allows fuel through but not at required rate.
Needle valve stuck.

Another problem you may look for.

Oil sending unit that tells the control board you are needing oil, This could be why need service light lights.
Consider that once the oil is distributed in the passages in the engine the oil level may be to low.

My best guesses based on not seeing the generator and troubleshooting.

 

[Mel]

Sounds to me like you are running out of gas.

Possible problems:
Below 1/4 tank of gas.
Filter allows fuel through but not at required rate.
Needle valve stuck.

Another problem you may look for.

Oil sending unit that tells the control board you are needing oil, This could be why need service light lights.
Consider that once the oil is distributed in the passages in the engine the oil level may be to low.

My best guesses based on not seeing the generator and troubleshooting.

Thank you for the response Kevin, I've exhausted all of my ideas so I really appreciate your's!!
It's not a gas running out issue I don't believe as I disconnected it after the fuel filter and hit the prime button and it squirts enough gas to be fine. Tank is 3/4 full of new gas. Also had same symptom when I put bypassed the tank and put the fuel feed line down into a gallon of fresh gas. I haven't changed the fuel filter as it is relatively new and based on the above test felt it was good but I might as well try that first as it would be a cheap fix. I will look into the needle valve I don't know where it is or what to do if it's stuck-will investigate that!
I had the oil at the full level when I started troubleshooting my issue. I then watched some YouTube videos that indicated the full status on Onan genies is wrong and it should actually be kept at 1/4 up from the bottom of the fill line so I reduced it to that but it didn't fix it!! I really thought that was the issue as so many videos were made about it but sadly no enchilada! So the symptoms were the same when it was "full" of oil as well as when I reduced the oil level.
I will look into the oil sending unit but again I dunno where it is but will investigate that too!
Thank you once again for your ideas and time!!

 

["EZ"]

Since it is running for a minute or two and I'm assuming it is running good (?) while it runs before shutting off, it sounds to me like one of the sensors may be bad. Low oil? High temp? They would allow the engine to start but would shut it down after it started. If it was a carb issue I think you'd have trouble with it running bad or running rough or not starting at all. My generator on my Class A is diesel powered and flashes "codes" when something is wrong. It's a different animal all together. So, I'm going off my motorcycle and car engine experience. I'm not even sure if you have a carb or F.I. but most will have the sensors I mentioned.

Good luck! Let us know how you fix it.

 

[Mel]

Since it is running for a minute or two and I'm assuming it is running good (?) while it runs before shutting off, it sounds to me like one of the sensors may be bad. Low oil? High temp? They would allow the engine to start but would shut it down after it started. If it was a carb issue I think you'd have trouble with it running bad or running rough or not starting at all. My generator on my Class A is diesel powered and flashes "codes" when something is wrong. It's a different animal all together. So, I'm going off my motorcycle and car engine experience. I'm not even sure if you have a carb or F.I. but most will have the sensors I mentioned.

Hi EZ and thanks for your response!
Yeah it's purring like a kitten for that 3 minutes and even for the subsequent 20 seconds after it dies the first time so I really don't think it is gas related IMHO...I am going down the oil sensor and temperature sensor wormhole now will report back either way!
Thank you for your time!

 

["EZ"]

Hi EZ and thanks for your response!
Yeah it's purring like a kitten for that 3 minutes and even for the subsequent 20 seconds after it dies the first time so I really don't think it is gas related IMHO...I am going down the oil sensor and temperature sensor wormhole now will report back either way!
Thank you for your time!

I know you're unemployed so do the free stuff first. Make sure the wires are not loose that go to the sensors before replacing the sensors themselves.

Good luck!

 

[Mel]

I swapped the year old carb and it's fixed, I figured that was a cheaper option than pulling it and putting it in the shop and if it didn't work I'd have a spare carb. I'm so relieved! Thanks guys for your helpful responses!

 

[Scooterfan]

Did all the stuff you did...then while running began playing with the mixture adjustment on the carb and immediately found the sweet spot...runs perfectly now. Look for the adjustment screw (maybe have to remove the air filter) and give it a try if it ever happens again. New carb is a better solution Of course, I don't have that RV anymore...but was told it's still running strong.