Onan Genset start problem

flapwing · 01-21-2020, 03:05 AM

Hello forum.... I tried to do my monthly exercise of my Onan generator (2016 Vista 27N). I hear the starter spinning but not engaging the motor to start. Also the inside ceiling lights dim considerably during the press of the start switch. The unit is on shore power with chassis and coach switches on. Any advice before I take it to a Cummins RV service center?

Lv2Roam2 · 01-21-2020, 07:17 AM

Try starting your main engine - let it run about 10 minutes - then try gen start. With your interior lights dimming suspect a battery issue - perhaps a loose ground or connection, a bad cell, etc.

If either your coach or chassis batteries are showing a low voltage when not on shore power that may help narrow the search.

Winterbagoal · 01-21-2020, 07:18 AM

Start chassis Ford engine, and let it run for 5 minutes, then try starting Onan while chassis engine is still running. Coach batteries may be a little weak or low.

EDIT: Or, do what Steve suggests.

Morich · 01-21-2020, 09:03 AM

Depends on what the sound is that you describe. To me, I would suspect more indepth problem if the starter is spinning but not engaging to turn the engine.
But if you mean the genset engine is turning but not starting, more battery power "might" help and cranking it longer may also be needed as there are times when the fuel takes longer to get to the engine or cold weather makes it slower to start.
My first thought by what you've told us, is that the mechanism between the genset starter and the engine is not flipping into the right location to tie the starter to the engine and that may be as simple as lube in the right location or as difficult as rebuild the starter.
This will not be the one for your engine, likely but an example:
https://www.ebay.com/i/291109469045?...xoCcpQQAvD_BwE
The gizmo at the end of the starter shaft has to move to engage. Perhaps it is not moving?

flapwing · 01-22-2020, 01:23 AM

OK... talked with the Cummins tech support at the service center. He advised to try and reach in and see if the fan attached to the motor can be turned by hand. It was free so the flywheel / motor was not seized, Conclusion... bendix gear to be replaced. This is one time the 3rd party warranty is a good idea to have.

Morich · 01-22-2020, 08:43 AM

Sounds like you got the right info going! Never woked on that part of a genset but they are pretty much like older cars on the starter and how it flies out to engage. Any mention of them being able to repair just the Bendix, rather than replace the whole starter? Old days, when the Bendix went out, the DIY guy had to change the whole as it was factory built together. For poor boys, we could sometimes get by with freeing it up so it would slide and engage but that was usually a short term fix and we had to redo it again in a few months!
Far better to have something to pay for a real fix. Glad to hear you got lucky on that point. I've often wondered why I have insurance/warranty on things as it sometimes comes out pretty useless.

kcgrant43 · 01-26-2020, 07:22 PM

Try priming it by pressing on the bottom of the start switch at the gen set.

HappiHenri · 01-27-2020, 12:20 PM

I have heard that some Onan's have a problem with the flywheel ring gear breaking, which would cause your problem. The only way to be sure is to remove the starter motor and peer into the opening to see if the ring gear has teeth looking normal - or not.

If all looks OK then it may simply be that the sliding gear on the starter motor shaft is not moving down to engage the flywheel. That is much easier to clean up & lube (if not broken).

Good luck

SocioSam · 01-27-2020, 04:45 PM

Quote:

Originally Posted by HappiHenri

I have heard that some Onan's have a problem with the flywheel ring gear breaking, which would cause your problem. The only way to be sure is to remove the starter motor and peer into the opening to see if the ring gear has teeth looking normal - or not.

If all looks OK then it may simply be that the sliding gear on the starter motor shaft is not moving down to engage the flywheel. That is much easier to clean up & lube (if not broken).

Good luck

We've had the same problem several times. One time it wasn't getting propane after the changing a recall problem. The repair people did not bled the system. We finally got it going after we bled the system via the the stove.

Second time we were told a fuse was blown. They never told us what fuse it was - we asked but got brushed off. They must have tried to bled the system first as they drained about half of our propane to fix the problem.

Morich · 01-27-2020, 05:13 PM

It might be worth noting that the OP has determined the fault is the Bendix not engaging. The bendix is the gear at the end of the starter shaft which has to engage as the starter turns. If it doesn't move, the engine is not cranked and will not start.