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Author Topic: ONAN 4000 won't stay running  (Read 489 times)

bigguyone

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ONAN 4000 won't stay running
« on: August 11, 2019, 10:03:16 PM »
Still having prob   runs as long as I hold start switch. 4.0 KA-FA/ 26100H.    Talked With a few on here about what mite be wrong, most said voyage reg could be bad. I got a new one in and installed it but still have sam problem. If the battery is dead will the generator do this? I know they say if there is no A/C it could do this.  I have 12 volts at the breaker.  I know there is other wires in the plug that can be checked for 120 votes but not sure what ones.
Thanks for any help on this, Dave

Isaac-1

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Re: ONAN 4000 won't stay running
« Reply #1 on: August 11, 2019, 10:56:21 PM »
does yours have the illuminated start/stop switch which will display blink codes?  I know that was introduced somewhere around spec H
2002 Safari Trek 2830

bigguyone

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Re: ONAN 4000 won't stay running
« Reply #2 on: August 11, 2019, 11:31:45 PM »
No its just start/ stop and 5 AM fuse

thesameguy

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Re: ONAN 4000 won't stay running
« Reply #3 on: August 12, 2019, 12:50:46 PM »
My 4000 developed a problem running after it sat for a while (~year). I replaced the the fuel pump with an external Facet pump, cleaned & rebuilt the carb and it's generally been good since. Very rarely it will die while warming up, but it restarts without an issue and keeps going. I suspect there is probably a minor adjustment issue, but since it's stored at sea level and gets most of its use at 5000+' it's been tough to dial in.

skydivemark

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Re: ONAN 4000 won't stay running
« Reply #4 on: August 12, 2019, 02:39:04 PM »
It could also be the control board.
This place http://www.flightsystems.com/ gives free troubleshooting guides. Also if you think it's the control board they will test it for $50 but usually wave the fee if you buy a new one from them. Some control boards they can repair, some not. They also have new after market boards for considerably less $$ than the Onan brand original that have a good warranty.
2015 Thor Four Winds 31L
Clermont, FL

Lou Schneider

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Re: ONAN 4000 won't stay running
« Reply #5 on: August 12, 2019, 02:50:41 PM »
The first thing to do is put a voltmeter on the generator output leads, either at the transfer switch or on the generator, whichever is more convenient, and see if the generator is making AC voltage when it starts to run while you're holding down the Start switch.

If it does make voltage, you have a control board problem or maybe a low oil pressure switch that's disabling the engine when you release the Start switch.  If it doesn't, then it's a voltage regulator or an internal generator problem.

Besides their free troubleshooting guides, Flight Systems has complementary 30 minute RV generator troubleshooting phone support.  Go to their website referenced above and click on "Book Now" at the top of the page to make an appointment for them to call you back.

They also make excellent, reasonably priced replacement boards if it comes down to that.
« Last Edit: August 12, 2019, 03:09:51 PM by Lou Schneider »

bigguyone

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Re: ONAN 4000 won't stay running
« Reply #6 on: August 12, 2019, 05:12:11 PM »
Hi and thanks for answering,  I have no transfer switch, but did check at the plugin, no voltage. I also checked at the breaker by the start/stop switch.  Has new carb new fuel pump. It did need them, Was running fine after putting  them on for about 8 months, then used it and next day it did this, was told by some on here it probably was regulator so just put a new one on, but still same thing. There is no light that would give any code, I guess this model don't offer that kind of control board.  I an not sure what wire you test to check gen it has two plugs, control board and regulator plugs. 
Thanks

Isaac-1

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Re: ONAN 4000 won't stay running
« Reply #7 on: August 12, 2019, 11:00:54 PM »
The later versions of the Onan KY 4000 integrated the control board and voltage regulator board into one, I thought this was done before spec H, but I may be wrong, I don't have my PDF of the service manual handy at the moment.

Either way it sounds like your unit is not putting out AC  power which is causing a shutdown by the control board.

There are a few things that can cause this, though the most likely and cheapest one, other than possibly a loose wiring connection, is a failed voltage regulator.
2002 Safari Trek 2830

Lou Schneider

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Re: ONAN 4000 won't stay running
« Reply #8 on: August 12, 2019, 11:27:34 PM »
Sounds like it's time for some systematic troubleshooting.  The generator needs excitation voltage from the regulator board running through the brushes and slip rings at the rear of the generator, then through the armature to generate the magnetic field that makes the electricity in the stationary coils surrounding the armature.

A break anywhere along the way will render the generator inoperative.  Since you replaced the regulator board the problem is likely elsewhere.  You may have a hung up brush that's not making contact with the slip ring, a dirty slip ring that's likewise blocking the excitation flow or an open winding in the field or stator coils.

The first two are easily fixable, the last is a major repair.

I'd get the Flight Service troubleshooting guide and watch their troubleshooting videos.  Follow the steps they outline to narrow down the problem, including taking voltage and resistance measurements.  And take them up on their free phone support if you get stuck.
« Last Edit: August 12, 2019, 11:30:56 PM by Lou Schneider »

bigguyone

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Re: ONAN 4000 won't stay running
« Reply #9 on: August 13, 2019, 07:52:15 PM »
Hi, yea I am going to try and look at the wires and plugs. Also I will try and test, if I can figure  what wires go to what.    well post what I find just have to find time.   
 Thanks for your help.