Onan starts and dies, throws Code 3

UPDATE I reread the codes, Flashes Fault Code 3, press STOP, Flashes Fault Code 23, Oil Pressure Fault Switch.

I followed the trouble shooting instructions and no problems detected. I also changed the filter and oil and I disconnected the Low Pressure Fuel Pump hose and the pump is working well.

Right now I feel the problem is in the control panel which is behind the carb and air intake and which I believe will require removing the entire generator. It is a pretty simple job but if I did that, I would be at the end of my knowledge. I would assume that a Onan authorized repair shop would also just change the control module or PC board or what ever it is called.

I would have to build a cradle to rest on my floor jack that would support the four corners of the generator. Too big a job and I have no space to do the work. I would have to do it in the street in front of the house and the DW would not like that.

Once again I must thank all of you that have responded. I looked through my literature from Winnebago this morning and looked parts for oil, air and fuel filters and will pick them up on the way home from the storage yard.

I then thought, Google the service manual, how smart we get too late. I found the manual, downloaded it to a DVD and found all the answers I hope I need.

To j-d, I did Google the manual and now I have it to take with me.

To bounder 39zman, you are right, the pressure switch is right there in the service manual and hopefully tomorrow I'll be able to check it out. I also reread the owners manual and have learned about all the things I did wrong regarding reading the codes, so tomorrow I'll follow the instructions.

As soon as I have checked out the codes again, and checked the oil pressure switch, I'll let you know the results.

Thanks again.

the oil pressure sw. on your set is a "normally closed" switch, which means when engine is not running, or no oil pressure, the switch contacts are closed. The switch opens on rising pressure. the switch is right out in open, near oil fill/dipstick cap. it has a single wire on it. the last occuring fault code is always available to recall.
when light in switch is blinking a "3" code, push switch to stop and release, now the 2nd level code will be displayed. 23 is code for faulty oil pressure switch. it can also set this code if wire is off switch, or open circuit in switch to control board wiring.
if light has quit blinking, you can get last code by pushing switch to stop for about 5 seconds, then push and release 3 times, light should now blink a 3 flash code. push to stop and release once more to get second level, 2 digit code

Do you have the Service Manual for it? We can search for it if you post Model and Spec.

Manual should tell you if the Pressure Switch is Normally Open or Normally Closed. From there, you could test by either unplugging it or shorting (maybe grounding) it. If it does keep running, replace Switch. But don't keep running it with Switch Disconnected or Bypassed. Something could actually be wrong!

I think many of the checks and safeties the ONAN has, are bypassed (ignored) in Start. Then you release the Start Button to RUN and it starts looking for trouble. I don't know if that's immediate when you release Start, or there's a delay before it starts checking.

Thanks for the info darben1. I am going out tomorrow(Saturday) and get the RV and I will replace the oil, filter and air filter as it is due. If that does not change things and allow the Onan to run, I'll figure out where the oil pressure switch is located and test the operation of the switch. If it checks out okay I'll see if the factory shop can look at it Monday.

Once again guys, thanks for the help.

Okay so Onan wired there low oil switches 2 ways/.
One way is the switch is normally open and low oil pressure causes the switch to close shutting off the motor.
The other is the switch is normally closed and oil pressure opens the switch allowing the generator to keep running. I do not know which is yours.
I do not know which you have but both automatically reset.

D.E.Bishop wrote:


I was just hopeing that someone wouls say thereis a magic reset chant I could make to cancel the fault. In fact I still do.

If you are old enough you remember old joke (involving Bill Gates) about resetting the car who die on the freeway by closing the doors and cycling the ignition.
In reality this thing is happening, but when software glitch will fix itself this way, faulty sensor will not.
I spend $600 lately on on couple of sensors for my car plus $150 to reset the code at dealer.
You don't have my pity ;)

darsben1 wrote:
Is yours one of the models that code 3 just means you have to check for the code.

Yes it is and if I remember correctly, I checked and it was a Code 23/low oil pressure. I didn't have my user manual with me yesterday, but I think it did show a Code 23 yesterday. This failure occoured awhile ago and every time I'm at the storage yard i forget to take tools and the manual.

I was just hopeing that someone wouls say thereis a magic reset chant I could make to cancel the fault. In fact I still do.

All I know is that mine did that once and cleaning the air filter took care of it.