Onan Generator Won't Turn Over

[Brent Hohlweg]

Hi guys,

Wondering why my 12.5 Onan Genrator may not be turning over:

1. 180hrs total use.
2. Been using it regularly without issue for last couple months as we dry camp.
2a. Oil shows full, coolant is full.
3. Last week we had a hard time getting it to start in the cold weather. I was able to only get it to start once I had also fired up our coach - produced a big cloud of smoke out the exhaust once it finally started.
4. Today after multiple attempts to start the generator - both with coach engine on and off, it would not turn over.
5. The generator seems to labor away trying to turn over, white smokes comes out...

Could it be that our Coach Group 31 batteries are dying and with recent cold weather there just is not enough cranking power... and by trying to start the generator multiple times (never cranking more than 30secs and waiting 2 mins between attempts like the manual says) we have some how damaged the alternator ?

Any ideas would be totally welcome :-)

Cheers Brent

[Robert Mathis]

When you saw it won't turn over, do you mean nothing happens when you hit the switch, or that it turns and just never fires? If it doesn't actually turn over when the switch is pressed, you either have a battery problem or the starter or solenoid is bad. The described symtoms of hard start coupled with heavy white smoke would indicate a problem with injectors or fuel flow. Have you changed you fuel filter lately? How cold is it where you are? Are you using the battery boost (parellel) switch when trying to start it?

[Brent Hohlweg]

Hi Robert,

Thanks for the reply :-)

Sorry what I meant is that it gets power when I'm pressing the gen start button. However the gen just cranks like when you have a dead battery in a car and the alternator just can't get the car started. While I'm pressing the gen start button we can see white smoke keep puffing out the tail pipe.

We have have not changed the fuel filter. I also wondered if it maybe it got some dirty diesel in it and it's clogged up... But the Cat12 main engine had had no problem.

It is cold here now (Scottsdale Arizona and now City of Rocks State Park in New Mexico)... Both getting down to about 26-27F overnight.

But yesterday I drove 4hrs to this State Park in New Mexico and arrived around 4pm and tried to start generator and we could not get it to start (as described above)...it's been just over the last couple weeks it seems to have started having these issues. We've been able to eventually get it to start (with a giant huge white/blueish cloud of smoke - like what happens when a car backfires).

PS: Funny you mention the "start booster"...Two days ago I tried that and was able to get it to work (but it created that giant cloud of smoke). That is also partly what made me wonder if the Group 31 batteries were dying)?

** How often should the fuel filter be replaced?

Cheers Brent

[Tom and Pam Brown]

Brent,

If you depress the switch in the opposite direction it primes the fuel and gives the glow plugs a chance to work longer.

Next time you try it mash the other side of the switch for a little longer time say a minute or so and then try to start it.

[Brent Hohlweg]

Hi Tom,

Thanks for your reply!  Yes I've been following the manual and doing up to 60seconds priming holding down the opposite direction of the gen start button... but alas even doing that plus using start boost while plugged in to 50amp power has still not allowed me to get the gen to fully turn on... It just cranks away like a car with a dead battery / alternator that cannot fully start (it's just puffing white smoke out the side while I'm holding down the gen start button).

Cheers Brent

[Gerald Farris]

Brent,
If your coach engine starts OK, the group 31 chassis batteries are OK. There is a possibility that the fuel filter for the generator is clogged, but it is a very remote possibility from your description. From your description of the problem, it sounds like you need to see a qualified Onan technician for the necessary repairs, unless you feel qualified to trouble shoot a diesel fuel system.

Gerald

[Brent Hohlweg]

Ok guys I made an appointment for tomorrow at Cummins Rocky Mountain in El Paso, TX to have them take a look.

**If anyone has any knowledge on what best to hace them service if I'm already paying them to look at this issue that would be great :-)

Cheers Brent

[Edward Buker]

Brent,

It should be that you have good batteries if it starts the C12. That is especially true if the C12 cranking seems to have normal cranking speed and is  not laboring to start. If that is the case you can assume the batteries are fine but you may still have a resistive connection between the batteries and the genset. That can be at a battery terminal, a stud type terminal where two wires of the battery harness going to the genset join, or a ground to the coach frame that is rusted at the battery end or the genset end.

When you say it cranks away like a car with a dead battery, that implies slow cranking and low voltage at the genset to me. If the cranking is slow and not normal for your genset you need to check those connections and sort out what the voltage is at the genset end while cranking. If you are not getting over 10V then that may be the source of your issue. A slow cranking diesel will bring in fuel but not have enough heat generated to fire the mixture. White smoke will be emitted and when it does finally start you will have a lot of smoke being emitted by the unburned fuel.

You might also check that no animal has nested in the air intake system/filter housing.

If the genset cranking is as energetic as ever and it just does not start then I would head in the direction that Gerald sent you and get some service...

Later Ed

[LarryNCarolynShirk]

Brent,

You may give this a try.  Hold down the start button for 3 seconds and let go.  Immediately, hold down the start button again.  Each time you push down the start button, the glo plugs heat up for a pre-established time and turn off.  That time may not be long enough for the cold weather you are experiencing.  The time period is about 3 seconds.  By heating the the glo plugs two or three times may be your answer.  It worked for me.  I learned this from a tech at the Onan dealer in Coberg, OR several years ago.  He discovered this short time-out on the glo plugs, when several coaches at a nearby rally experienced the same symptoms on a cold day.  It costs nothing to try.

Larry

[Robert Mathis]

Please let us know what the problem turns out to be. It does sound like low voltage to the starter, but one never knows. The genset on my boat got a clogged injector one night about 2:00 A.M. and started running rough with tons of smoke. Fortunately, the clog cleared itself after a couple of minutes and all was well. Since we were 80 miles offshore at the time, I was a tad concerned. How often you should change the fuel filters is dependant on the quality of fuel you buy and the length of time in the tank. We changed fuel filters about every 200-300 hours on our boat, but carried several sets of spares. On the Onan in the coach, we change it once a year, without regard to hours. The filter is fairly cheap and good insurance to us.

[Brent Hohlweg]

UPDATE:

Took our coach into Cummins Rocky Mountain in El Paso. After a full service and the technician diagnosising it as "air getting into the diesel fuel line"...because once he drain the line and did a full service (fuel filter, oil filter, coolant change)...it started.

BUT!

I was not feeling that confident, so we drove to the near by Heuco Tanks State Park were the following morning it did not start again. So I went and replaced my two chassis batteries as they were near end of life and needed to be done at some point anyways. But today the gen never started again, after a 2min glo plug warm up again it would not turn over (it's like the generator is just not getting enough power to turn over and start).

SO:
The gen set read at Cummins as getting 12.6 volts while attempting to turn over and start. So could it be that with new batteries and full servicing the issue is... The gen set connections from the battery are all rusted up and dirty after almost 10yrs and we're just on the edge of getting enough power to turn over the generator. I'll go underneath today and clean them up and see how that goes.

PS: I'll keep everyone posted and also will upload a photo from the Cummins shop where a guy with a 06 Beaver Monterey was having his entire gen pulled out at a cost of over $2000 :-(

[Norm Green]

My generator starts off the house batteries, not the chassis batteries.  Have you confirmed which batteries start the generator?

[Gerald Farris]

Brent,
If your generator has 12.6V at the starter when it is cranking, low voltage is not the problem.

Gerald

[Dave Cunningham]

Hi Brent, I have been following along here hoping I could offer some advise as I have had my share of generator issues, but the other guys seem to have covered all the basics, the main thing being ; getting over 10 volts to the unit on startup, I'm assuming that it does turn over ,but will not fire. Since you have just had it serviced , I would take it to a reputable onan shop and get them to diagnose again, and if it actually comes down to being a control board issue, it just occurred to me that I still have the one that I changed out of my last marquis, and I know that there is nothing wrong with it, when I bought the board I was told that the unit had to be removed from the coach to replace it , but that is not the case, it can be done with the genet slid all the way out.
The control boards for those 12.5 s are about $1100.00 so if you or anybody else reading this ever needs one I have it on the shelf.

Dave

[Brent Hohlweg]

Thanks for all the help guys!

I just fully cleaned the generator terminal connections and made them look brand new - nice and clean, but alas it still will not turn over. It just cranks and blows white smoke (seems dirty towards blue today - but that could be the couple attempts at starting the gen over last two days and it not successfully starting up).

I going back to Onan again and having them take a second review.