f271186 Report post Posted May 12, 2011 Our Onan Micro 4000 gas generator starts fine but won't continue to run. I have changed oil, spark plugs, given carburetor a several shots of carb cleaner. I am getting good fuel flow beyond the fuel filter to the carburetor, so it isn't the fuel filter. Now I'm stumped. Help? Share this post Link to post Share on other sites
tbutler Report post Posted May 12, 2011 I'm not familiar with the Onan Micro 4000 but our Onan 7500 has a series of error codes that display on the start button as flashing lights. The sequence of flashes indicates the code. We had ours act similarly, it turned out to be a faulty temperature sensor that was shutting the unit down, thinking it was overheating. We had the sensor replaced and it has worked fine ever since. Check your owners manual for the error code sequence or call Onan for instructions on how to get a code if yours does display one. So now I've read your sub-heading, and yes you do have error codes and you have read them! I'd guess a faulty sensor of some kind. You might call Onan, give them the code and get their ideas for solutions. Share this post Link to post Share on other sites
GilbertRushia Report post Posted May 12, 2011 I agree with TButler; except I had a small leak in my radiator and the gen was slightly over heating and would shut down until it cooled. Good luck! Share this post Link to post Share on other sites
wolfe10 Report post Posted May 12, 2011 I agree with TButler; except I had a small leak in my radiator and the gen was slightly over heating and would shut down until it cooled. Good luck! We may be getting off track here. The 4000 is air cooled, so a leaking radiator will not be his issue. You might give Onan a call to verify that your generator does give fault codes and/or ask them for advice on troubleshooting: 800 888-ONAN. Brett Share this post Link to post Share on other sites
hermanmullins Report post Posted May 12, 2011 We may be getting off track here. The 4000 is air cooled, so a leaking radiator will not be his issue. You might give Onan a call to verify that your generator does give fault codes and/or ask them for advice on troubleshooting: 800 888-ONAN. Brett I agree, the 4000 is air cooled. I also beleive it is a splash lube engine. I don't think it has a low oil sensor. I had a 4000 some time ago and it did get hot due to poor air circulation, it did not shut down and melted most all of the plastic parts in the gen. side. Burned up the stator, cost high, replaced the gen. GOOD Luck. Share this post Link to post Share on other sites
desertdeals69 Report post Posted May 12, 2011 Does it stay running if you continue to hold the start button in? If so it maybe the voltage regulator. Share this post Link to post Share on other sites
cuilirish Report post Posted May 13, 2011 Our Onan Micro 4000 gas generator starts fine but won't continue to run. I have changed oil, spark plugs, given carburetor a several shots of carb cleaner. I am getting good fuel flow beyond the fuel filter to the carburetor, so it isn't the fuel filter. Now I'm stumped. Help? This may seem obvious to most but... something as simple as not having ALL breakers on at the panel can cause a Onan generator to short cycle and continuously shut off in cool down mode. Share this post Link to post Share on other sites
f271186 Report post Posted May 13, 2011 Thanks to all of you for your help. We took the suggestion to call Onan. Diagnosis: Varnished carburetor or gummed up shut-off solenoid. Parts about $150 and labor should be about 1 hour. Too hard to do it myself so have to take it somewhere. Thanks again Share this post Link to post Share on other sites
f271186 Report post Posted May 16, 2011 Further update: Went out to check solenoid. Noticed that bowl of carburetor looked a bit different. Took the bowl off. It was FILLED with gel. Cleaned the gel out. Put back together. Started 'er up. Bingo! Purrs just like it used to! Yea! Will see if our good luck continues. Share this post Link to post Share on other sites
wolfe10 Report post Posted May 17, 2011 Thanks for the update. Another reason to run the generator monthly for 45 minutes minimum under 50% minimum load. Along with drying out the electrical part of the generator, it keeps fresh fuel in the carburetor. If you can't run it while stored, consider disconnecting the fuel line and with no load on the generator, running it out of fuel. Brett Share this post Link to post Share on other sites
f271186 Report post Posted May 17, 2011 Thanks for the update. Another reason to run the generator monthly for 45 minutes minimum under 50% minimum load. Along with drying out the electrical part of the generator, it keeps fresh fuel in the carburetor. If you can't run it while stored, consider disconnecting the fuel line and with no load on the generator, running it out of fuel. Brett If we are lucky and this cleanout works...you can bet we will run that generator the first of each month winter and summer! We use the generator in the winter to power things in the house during power outages. It is just that this year we only had 2 outages so it didn't get its usual work out. Thanks for the info on running fuel out the generator if we aren't needing the RV for a few months. Appreciate your help. Judy Share this post Link to post Share on other sites
desertdeals69 Report post Posted May 18, 2011 Running the gen with a disconnected fuel line until it stops does not run all of the fuel out of the bowl and other parts of the fuel system. There is still fuel left that turns to a thick brown looking varnish. To prevent this from happening use a fuel stabilizer mixed in the gas prior to shut down. Make sure it is mixed in the gas tank, usually 1 oz per gallon and then run gen long enough to get the treated fuel into the whole system. This will also be beneficial for the main engine. This should keep the fuel usable some 6 to 12 months latter. The fuel stabilizer is available from Onan or even a product called Stabil at Walmart. Share this post Link to post Share on other sites
leisureflytes@hotmail.com Report post Posted December 22, 2017 On 5/11/2011 at 7:18 PM, F271186 said: Our Onan Micro 4000 gas generator starts fine but won't continue to run. I have changed oil, spark plugs, given carburetor a several shots of carb cleaner. I am getting good fuel flow beyond the fuel filter to the carburetor, so it isn't the fuel filter. Now I'm stumped. Help? Check the antifreze,if its low it'll shut down!! Share this post Link to post Share on other sites
wolfe10 Report post Posted December 22, 2017 leisureflytes@hotmail.com, Welcome to the FMCA Forum. The Onan Micro 4000 is an air-cooled generator-- no antifreeze (coolant) to check. The thread is also 6 1/2 years old. Share this post Link to post Share on other sites
manholt Report post Posted December 23, 2017 Your not the first, nor will you be the last, to post on a old thread. Share this post Link to post Share on other sites
wildebill308 Report post Posted December 23, 2017 21 hours ago, leisureflytes@hotmail.com said: Check the antifreze,if its low it'll shut down!! Welcome to the forum. I had a diesel generator that was doing just that. It was traced to silica crystals precipitating out of the coolant. They had used the wrong coolant. This was during my final PDI and the dealer had to replace the radiator. I recommend using only low silica antifreeze. Bill Share this post Link to post Share on other sites
hermanmullins Report post Posted December 23, 2017 Hay Bill, where do you put Anti-Freeze in an AIR COOLED Generator? Herman Share this post Link to post Share on other sites
wildebill308 Report post Posted December 23, 2017 22 minutes ago, WILDEBILL308 said: I had a diesel generator that was doing just that. Bill Share this post Link to post Share on other sites
