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Open Roads Forum  >  Tech Issues

 > Onan Emerald 4000 won't crank

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The Hamilton Hovel

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Posted: 08/29/09 09:40am Link  |  Print  |  Notify Moderator

Hi,

I've always found the help I needed by serching the site but haven't been able to find this one..... HELP!!!!

I have a 1993 Class C Shasta with a Onan Emerald 4000 genny.
Problem: It's always run fine until this season. I haven't started the genny in the last 10 months... (yeah, I know - DUMB!) and now all I get is a 'click' when either the remote or on-generator 'start' button is pushed. I've cleaned all wires, drilled a new hole in the frame & re-grounded it already and still the 'click' only. So, I used jumper wires from a very good battery and positive to the on-generator terminal and negative to the engine 'fins' and still the 'click' only. Meter shows plenty of power/current/amperage going to the unit.

I'm thinking a bad starter motor or 'stuck' starter.

The generator is in a cavity as tight as you could ever imagine so pulling it out is going to be a beast of a job. I'm hoping the starter motor will be accessible from the front???????

Any ideas?

Thanks in advance for any of you taking the time to reply.

f.

Old Salt Chief

Edenton, North Carolina

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Posted: 08/29/09 09:53am Link  |  Print  |  Notify Moderator

Mine had the same problem, and I took it to a Cummins maintenance facility - they own the Onan brand. The tech showed me that the generator, when last run, had stopped on the beginning of the compression cycle, and the carbon build-up prevented the piston from moving. His simple fix - reach into the rear of the left side, with power OFF. You will feel a fan blade there. Just turn the blade about a half turn - this also turns the crankshaft on the gen. Now it will start normally. He said that the gen has to be "de-carboned" regularly, to prevent this. Works for me.





Chris Bryant

DeLand, Florida, USA

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Posted: 08/29/09 10:53am Link  |  Print  |  Notify Moderator

On the Emerald you can also turn it with a 3/8" allen wrench from the right side.


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Chinook

Missouri

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Posted: 08/29/09 10:53am Link  |  Print  |  Notify Moderator

I think that I concur with the previous poster somewhat, but I am not sure about the carbon buildup.

This appears to be sign of a low battery or bad cable connections with the resulting “stuck starter”. I had a similar problem with my generator. I checked it before a trip to Alaska and all appeared to be fine. Used it a couple of times on the trip and then it wouldn’t start. It got to the point that it wouldn’t turn over and just made a click (klunk) that sounded as if the starter was jammed. After returning home, I found information this forum that explained that sometimes the piston in the engine could stop near the top of the compression stroke and the starter motor then could not turn the engine over. The solution was to turn the engine over by hand so it was past the top of the compression stroke. I found that by putting a wrench on the nut on the flywheel, I could get the engine rotated past the compression stroke. I also discovered that I was getting a big drop in the 12 volts as I tried to start the generator. As a test, I used jumper cables from my truck directly to the generator (negative to generator frame – positive to battery side of starter solenoid) and it started instantly. In my RV, the frame was used for the negative wire and the connections from the frame to the generator had corroded and although I could get a 12-volt measurement, the corroded connections would not allow enough current to pass to run the starter. In addition to replacing the corroded connectors, I ran a heavy gauge copper wire from the battery ground to the starter ground. This solved my problems. As stated above, a large drop in voltage when trying to run the starter indicates a bad connection. You might need to check ALL of your ground connections from the generator all the way back to the batteries.

A bad electrical connection increases the resistance in a circuit. Ohm’s Law states E=IR where E = voltage I = current and r = resistance Since the battery voltage will not increase (it actually decreases with each attempted start), increased resistance causes a decrease in current. With a decrease in current, the starter motor produces less torque (turning effect) because the magnetic field produced in the starter is proportional to the current. When the piston in the motor’s cylinder goes upward during the compression stroke the volume of the area from the top of the piston to the bottom of the cylinder head becomes less, According to Boyle's law, if you reduce the volume of a quantity of gas, the pressure will increase. When the force of the gas pushing down on the piston (pressure) equals the torque of the starter the starter motor stops turning. Attempted restarting does nothing to change these forces and the starter motor in an attempt to turn just runs the starter bendix into the flywheel producing the clicking sound. By physically turning the motor past top dead center, by pulling on flywheel or placing a wrench on the flywheel nut, the piston starts on its downward stroke and the pressure becomes less so that the torque of the starter is adequate to rotate the motor.





The Hamilton Hovel

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Posted: 08/29/09 12:49pm Link  |  Print  |  Notify Moderator

WOW!!!!!!!!!!!!!!!!!!!

Talk about FAST help !

Thank you VERY much. As you would guess, We are on the road today & tomorrow - back home on Tuesday & out again Wednesday & Thursday.

If I can get a shot at the fan and/or crank tomorrow when we park I'll give it a try, otherwise it'll be Tuesday.

I'll keep ya'all posted, and thanks again!

f.

The Hamilton Hovel

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Posted: 09/13/09 01:14pm Link  |  Print  |  Notify Moderator

Sorry it took so long to respond with 'results' but here it is.

I was able to get an allen wrench on the right side of the crank and spin it a couple of turns - tried the starter switch and again, just the same sound of a single relay 'click' right there in the generator area. I guess I'll have to pull the unit out. The way it looks, the unit is bolted to the bottom of the 'bin' it's housed in and must be moved out though the door opening. It's tight, VERY tight. It almost looks as if they installed the Genny & then put the outside walls up afterwards.

I see the (+) battery terminal wire in front & a few harnesses that can be unplugged for removal. The exhaust has to be removed because it goes through the bottom plate.

Are there any other ideas out there before I do "The Big Nasty" removal? Or any other thoughts that could be tried before I remove it?

Again, thanks for all the help & concern. It's truly appreciated.

f.

Generator Jim

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Posted: 09/13/09 01:42pm Link  |  Print  |  Notify Moderator

I would open the control panel cover and see about jumping the start solenoid to see if it's good. This would prove or disprove the starter without disassembly.

JimL


Jim & Jane Latour
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Handbasket

Asheville, NC

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Posted: 09/13/09 02:45pm Link  |  Print  |  Notify Moderator

If you do have to pull it out and it's too big, the door frame may be removable. The compartment door & frame on my Tiger have to come off to pull the Onan. If yours is similar, find the point where the rubber trim strip meets, peel it out, and remove the screws from around the frame.

Jim, "I've taken a vow of poverty. To annoy me, send money."


'06 Tiger CX 'C Minus' on a Silverado 2500HD 4x4, 8.1 & Allison (aka 'Loafer's Glory')

The Hamilton Hovel

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Posted: 10/12/09 05:48pm Link  |  Print  |  Notify Moderator

Thanks everyone!!! So here's "The Rest Of The Story"!

The generator had to be pulled. 1st the 'door' panel and frame came off, then the muffler needed to be 'torched' off. 4 mounting bolts removed along with wire(s) etc. Then the unit slid out on to a waiting milk-crate. (this is one heavy sucker!)

There was a steel enclosed cable about 1" in diameter that was long enough to snake out with the generator. The starter is in the right rear along with that infamous rear spark plug. Removed the starter & tested it with a 12 volt battery..... it was fine! Conclusion: Starter was 'dirty'. We dissembled the starter, cleaned up up reassembled, reattached and tested. Reassembled everything along with a new muffler and it's A-OK now.

While we had it out we replaced the plugs, oil & filter.

For any future need to pull the generator we redesigned the carriage that it's mounted in so it's now a smooth operation to remove 4 bolts and 'swing' the unit down under the chassie with everything totally exposed. Why couldn't they do that at the manufacturer?

It's taken me a long time to get the right weather & time conditions to do this and I thank you all for the great information & hints. It's been a real learning experience for me.

Again, thanks.

Floyd.

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