Onan 4000 generator troubleshooting?

I tried starting the generator in the RV the other day & it's completely unresponsive. There's no lights when I use the control panel inside, nor when I use the start/stop/prime switch on the generator its self.

So far I've:

• Made sure the RV has over 1/2-tank of gas(the generator shuts off/won't start if it's below 1/4-tank)
• Confirmed I have 12v to the generator 
• Confirmed the generator is grounded to the chassis
• Jumpered the 12v cable on the starter solenoid to the output side & confirmed it cranks. 
• Checked for the 12v signal to the starter solenoid, but it's not there

At this point I'm thinking the control board died, but before I spend $$$ for a new one is there anything else I should test?

Do you know an approximate build date of the genset? 

In reply to TJL (Forum Supporter) :

The RV is 2004 and I'm pretty sure it's original to the coach. 

In reply to Pete Gossett (Forum Supporter) :

Do you have the owners manual? Check for a circuit breaker tripped or blown fuse on the side of the generator 

There should be an oil level switch, but I think it should crank when it thinks there's low oil, just not start.

In reply to Indy - Guy :

I have both the owners & installation manuals. I'll look through them again, but I didn't see anything referencing a breaker or fuse on the unit. The only thing the troubleshooting section referenced was the various blinking codes on the control panel. 

wae said:

There should be an oil level switch, but I think it should crank when it thinks there's low oil, just not start.

 

That's intriguing because I discovered something weird about it. If it's sat unused long enough for it to cool off & the oil to drain into the pan, when you first unscrew the dipstick it's completely dry. But then when you screw it back in & check it again, the level is full. 

There should be a fuse somewhere for the generator. Possibly also a relay for the starter solenoid. Our fuses are mostly on one panel but there also a bundle of fuses & relays under the dash which I tracked down when the slides wouldn't move. It's always fun when rv electrical issues happen.  
Do you live in a high humidity area like Florida? We had so many electrical oxidation issues when we moved here. Now the charger/inverter & all ATS's are new. 

In reply to mdshaw :

I did check fuses. None were blown, nor did any of the labels mention generator. I'll Google the starter relay location & see if I can anything. 

We're a block from the Gulf, so definitely high humidity!

Look for a circuit breaker on the side of the control panel of the generator.

Check the voltage regulator.  My Champion 9500W (Dual fuel), would crank, no start.  I had inadvertently fried the regulator.  Replaced it, works like a champ

I second (third?) checking the circuit breaker. Such a simple thing, but I've seen it happen.

I just re-read the manual. The only circuit breaker is this one on the output of the genset. 

I tried it in both positions, but no change. 

I double-checked again with my multimeter: I have 12v from the battery into the starter solenoid, but pressing the start switch on the genset doesn't send 12v to engage the solenoid. I also disconnected the interior control panel & tried again, but got the same result. 

No doubt you already checked this, but in the Winnebago I had last year, I couldn't get it to start one time, similar to how you described it.  

I chased it for a few days.  Turned out to be I just hadn't plugged the main (high voltage) line into the generator output plug.

I was simultaneously relieved to have it running again and also a bit embarrassed.  It's a long shot, but I thought I'd mention it.

Hmm...it looks like this may be a good/cheap/redneck solution to get it working for way less than the cost of a new control module. 
 

I wanted to post my efforts to get an older Onan 4000 to start,  Spec E KY 1995 gasoline type version.    Hopefully this will help someone some day as all those other posts and videos helped me.

I got this unit for $400.  It was reported as not having a lot of hours on it and it was sitting in a storage unit not running for years.  It looked in very good condition which is why I bought it.

As received, this unit was not mounted in an RV.  I see guys replacing things without un-mounting from the RV  but that would frustrate  me beyond my limits.  Having it fully accessible allowed me to work on it freely. 

I easily found free downloadable versions of the owner manual and service manual online in PDF format.

My first attempt to start  it  I heard a  repeated clicking sound which sounded like a bad starter to me.   I first tried using a readily available lawnmower battery then I tried a car battery  but got the same results.

Since it had not been run in a number of years I decided to replace parts.

I used all amazon inexpensive parts;  replaced the carburetor, air filter, spark plug, fuel filter,  fuel pump,  starter and solenoid (all for about $100 ).  I also replaced the gas line and put in a shut off valve which was included in the received parts.   I  changed the oil which cost $20 for a big jug as that's all they had at the time.    There is no oil filter on this version.

Replacing the two carburetor bolts was a pain in the.

After all that I still could not get it to turn over and it still made the repeated clicking noise.   

I then read about turning the engine over by hand with a socket set - without the battery hooked up obviously.   At first it was super difficult.  But then I got it to turn easily during 3 of the 4 strokes.  The compression stroke was a bit more difficult as expected but it did turn.    I next  removed the spark plug and it then tuned super easy during all 4 strokes.    I then knew it was not seized.  

I mucked with the new and old solenoid.  I wanted to learn how to trigger it by hand but was never able to do that with them outside the unit.  I put the old solenoid  back in the generator.  Disconnecting the starter and connecting the battery,  the on/off switch triggered the solenoid so I thought it was still ok?   With the spark plug out  I then turned, reconnecting the starter,  it turned over the engine when the start switch was pressed.  So I got it working without the spark plug in.   I then tried with the spark plug in - again back to the repeated clicking sound.  So I then measured the volts out - it was not delivering 12 volts out,  it was just above 11 volts.   During my research I learned a solenoid can go bad in a way that it limits output voltage.  I originally thought a solenoid would work or not work, but that's not the case.   The internal terminals get corroded over time and can reduce output voltage as I found out.   So I put the new solenoid back in and got 12 volts out.   

But still , with the spark plug in,  there was that damn repeating clicking sound when trying to start it.  I had read and saw an example of someone using a golf cart battery to turn over one of these,  which is why I was using a lawnmower battery I had laying around.   I then read up on the required DC amps for a 4000.  These need over 300 amps as stated in the service manual to turn over the engine.    The lawnmower battery I had was only 230 amps.   I then again hooked it up to the car  battery and it came to life - super smokey and it sucked down the little can of gas I was using to feed the gasoline.   Success at last... well at least I got it to  run.

Lesson learned

Remove the starter, put it in a vice or something to hold it and test it - in hindsight my old one worked just fine, I my not have needed to replace it.

Test the solenoid in place as there must be something going on in the wiring and control units needed for these to trigger.  Just like other solenoids, these make a distinctive click when activated.   Measure the backside voltage to ensure you get 12volts just as you put in.  Be careful not to touch ground when checking output voltage. otherwise you'll need to replace the 5 amp fuse as I did.

Replacing a spark pug is always a good idea

Replacing the fuel pump and filter is always a good idea - way much easier if unit is not installed in the RV

Replacing carburetor after the years of no service was required -  upon inspecting my old carb I noticed the throttle plates were gummed and stuck open- also easier  if the unit is not in RV.

Have good ventilation,  this one smoked up my shop in seconds.

My next steps are to get it running more cleanly - I  suspect it will simply take some extended running time to clean itself out.   It does need a solid secure mounting or floor to run on for any period of time.   I had mine up on  a make shift lift so I could drain the oil which was obviously not solid enough for it to run for an extended  period of time.

I also need to see what output voltage it will create

Hope this helps someone in the future