I have an Onan Emerald III generator that runs on propane that I cant get going

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I have an Onan Emerald III generator that runs on propane that I cant get going

December 05, 2011, 06:21:51 pm

When I first got the Coach the generator started fine the first couple of times.Then It started cranking too slow to start and now wont crank at all. That is unless I run a jumper cable from my battery jump box to the starter solenoid. Then it will just barley crank over but not enough to start..

Without help from the jump box she just clicks. I tried to jump from one side to the other on the solenoid with the same results.

I pulled the plugs and this allows it to crank over faster but still not at all without help.

It has a fresh coach battery and I am getting 12 volts at the battery side of the starter solenoid. The starter is not easily accessible.
I cant get a reading from the starter side of the solenoid. It just jumps around while its clicking.

In the extra parts I got with the Coach there was a new starter solenoid, so I went ahead and installed that. Also in the extras was an old starter for the generator and I can see the edge of the one in there and it looks fairly new.

I cleaned up the grounds that I can get to. Anyone have an idea what my problem might be?

Thanks Tony

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #1 – December 05, 2011, 07:15:17 pm

Tony, I would look for a faulty ground. If you have 12V at the starter solenoid then look for a ground strap. If genny is on a slide out tray there may be a flexible strap. As a start, use your jumper cables from good clean spot of genny to frame ground or better yet back to battery negative. I wish I knew more about Propane gennys but its been years since I had one.
Good Luck
Gary B

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #2 – December 05, 2011, 07:39:36 pm

After confirming that the battery that is used to start the generator (usually, but not always the house batteries) has 12+ VDC both at rest and while cranking, the next step is check voltage between the red cable/generator starter lug and generator body. If less than 12 VDC while cranking, check from that positive lug to good, clean chassis ground. If voltage is higher, as Gary said, you need to clean the ground connection from generator to chassis (or add one if it is on a slide out tray and the tray itself (i.e. bearings themselves) are the ground path.

If you have 12+ VDC from generator starter lug and generator body, it is a problem in the generator itself.

Brett

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #3 – December 05, 2011, 07:43:54 pm

Gary's comment is a good one and I believe it to be the problem. I had the same generator in a previous MH and it was very very easy to start and virtually no problem for the eight years I owned it.

Allan

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #4 – December 05, 2011, 08:17:43 pm

Allan,

Gary and Brett have pretty much covered the possibilities with the ground the most likely suspect. An additional test would be to put a voltmeter on the starter solenoid and check voltage before and during cranking. Before cranking, you should see battery voltage at the solenoid. If you have to add a ground strap, a braided strap has a little advantage over a conventional cable as it takes flexing from the movement of the generator a little bit better without fatigue at a connection. Grounding through the ball bearings on the slideout tray is not the best as Brett also mentions.

Starters do go out but normally just quit (but not always) rather than cranking slower. Slow cranking if due to a corroded or loose connection will generate some heat at the problem area. You could also feel for any unusual higher temperature
at connections.

Operating the starter at less than full battery voltage will shorten starter life over a period of time.

Pierce

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #5 – December 05, 2011, 08:24:42 pm

Quote from: Pierce & Gaylie Stewart – December 05, 2011, 08:17:43 pm

Operating the starter at less than full battery voltage will shorten starter life over a period of time.

To amplify on this, you should have *more* than 12vdc at the starter terminal. We always talk about 12-volt systems but a battery that measures exactly 12-volts is nearly depleted. A fully charged battery should have somewhere around 12.5 volt. It doesn't sound like much but it makes a big difference.

So if you measure exactly 12vdc at the starter solenoid you might also look for a lossy path back to the battery bank (corrosion, loose terminals, etc.).

Craig

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #6 – December 06, 2011, 06:40:49 am

Thanks so much I will I will take another run at the grounds this afternoon

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #7 – December 07, 2011, 08:35:57 am

FWIW - the installation in my coach used the generator support frame mounting points to supply a ground path. There was a bonding strap between the generator and generator pan - from there the pan was bolted to a frame, and the frame bolted to the bay floor and coach frame. If there is corrosion on the attaching hardware or attachment area, then the ground path will be compromised. I'm redoing the gen area, and have added a dedicated ground cable from the gen body to the frame.

A quick way to confirm would be to take one jumper cable and fit to a good spot on the engine or generator body, and fit the other end to the coach frame. If it cranks properly at that point, that's the problem.

Hope this helps.
Steve

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #8 – December 07, 2011, 10:19:29 am

I also ran a 00 cable from generator to chassis ground on mine.

Brett

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #9 – December 07, 2011, 03:34:05 pm

All of the above sounds great, and assuming the starter motor, battery and wiring are up to snuff, I would be looking at the oil issue. Don't laugh, but have seen one Onan with 90 wt gear oil in the crankcase, was hard to turn over, also seen no oil, it was also hard to turn over. There are other reasons why they are hard to start than just poor wiring, solenoids etc.
Just food for thought or FWIW.

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #10 – December 07, 2011, 05:49:36 pm

Or a low oil sensor is making the engine start hard or not at all if its defective or there is not enough oil in the crankcase.

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #11 – December 07, 2011, 06:00:17 pm

Quote from: Donmystic1 – December 07, 2011, 05:49:36 pm

Or a low oil sensor is making the engine start hard or not at all if its defective or there is not enough oil in the crankcase.

No, the symptoms described in his first post are not that of a problem with the oil pressure sender or its circuit.

Were the engine starting and dying it would sure be a consideration. But his doesn't turn over fast enough to start.

First suspect (easily verified with voltmeter) is an electrical issue, hence all the posts on that. Then, as Dave said, after ruling out the likely stuff, time to get into the "other stuff". To me that starts with carefully reaching in and rotating the engine by hand to verify that is is not seized.

Brett

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #12 – December 07, 2011, 07:54:06 pm

Brett, I have seen many real funny issues with these RV gensets, from the 90 wt gear oil the son in law put in the engine to snakes all tangled up and made into soup that bound the engine up, had to remove the field to clean up. Never a dull day. Another is running low on oil on units with the splash lube system, they will snug up nice & tidy too, babbit welded to the crankshaft etc, real joy for owner. The other funnies are when they have been run low on oil, then refilled with fresh clean oil, they would be smarter to fill up with some old drain oil, at least it would look plausable until you get to the babbit on crank.

Oh Joy

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #13 – December 07, 2011, 10:40:34 pm

Or he has water in the cylinders causing it to hydrastaticaly (sp) lock up. Pull all the plugs and see if it spins freely.

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #14 – December 08, 2011, 12:20:40 am

Less'n his motorhome been in a flood, that ain't likely.

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #15 – December 08, 2011, 08:44:02 am

Cooling water entering cylinders from a crack somewhere.

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #16 – December 08, 2011, 09:00:18 am

Quote from: Donmystic1 – December 08, 2011, 08:44:02 am

Cooling water entering cylinders from a crack somewhere.

It is an air cooled generator.

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #17 – December 08, 2011, 11:34:45 am

Then the flood sounds better

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #18 – December 08, 2011, 11:36:29 am

Quote from: Donmystic1 – December 07, 2011, 10:40:34 pm

Or he has water in the cylinders causing it to hydrastaticaly (sp) lock up. Pull all the plugs and see if it spins freely.

Sorry for a little fun. Our Netflix came and I posted while I was watching the my first Mary Hartman, Mary Hartman. Someone murdered a neighborhood family along with their 2 goats and 8 chickens.

Keep posting and I will keep my humor to myself. Gaylie regularly serves up Crow Cake to me for all the stupid things I do.

Pierce

Re: I have an Onan Emerald III generator that runs on propane that I cant get going

Reply #19 – December 10, 2011, 10:15:31 am

I just saw this thread.

I'm not sure what Tony means by the battery jump box but if Tony was using normal jumper cables, there should not be a ground issue since the cables are supplying the power and the ground. Therefore it seems to me that either the problem is starter drag, pretty likely, or as Dave said an issue with the oil causing too much friction.

I would drain and refill the oil as my first approach since it is cheap and can't hurt a thing. Then spin the starter with the plugs out to lubricate the engine. If that doesn't work, pull the starter and have it checked out or replaced.

Definitely try jumping the starter from a car or a hot battery other than that on the coach.

Good Luck!!

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