Faulty Onan Generator Options?

[Tadrith Bear]

Hello So I'm looking for opinions. The used class C RV I just bought has a non-working Onan 4000 generator. I can hear the starter click, but it doesn't turn over. The Hobbs meter says it has a little over 1400 hours on it. I've heard that 1500 hours is the expected end of life for that generator model.

Is it worth it to try to fix this one myself, or just chalk it up and get another one?

[wahoonc]

It might be worth spending a little time to get it running, however, I wouldn't go overboard spending money on it. A replacement of the same type is $4300+.

Aaron

[Morich]

I would certainly want to look closer before ditching it.
What you have is very commonly a dirty battery cable. Possibly not but worth a look?
Have you had any cars which did the same "click" and would not start or even turn over?
Same issue and very much the same system!

Their is a battery, likely the coach batteries, which feed power to a solenoid on the generator starter. This solenoid is a fancy name for a set of contacts which close when we turn the start switch. There is a cable from the battery to the solenoid, when we hit the switch, the contacts close and the power it then connected to the starter motor to turn the engine. Just like a car starter works but less added gizmos.

What often goes wrong is that the cable from the battery to the solenoid get corroded and there is not enough power getting through to turn the motor! One thing to check is that cable is good and clean to make good connection!
But is also fairly common for the coach batteries to be weak! Not enough power to make the starter turn, so one way to make better chance of good battery power is to start the RV engine first.

When the engine is running the chassis battery and alternator should be connected to the coach side and that give the generator the best chance of having enough power to turn and crank long enough to get fuel and start!

Maybe weak batteries, maybe dirty cables or it COULD be something really wrong, but I would not ditch it just yet. RV are famous for setting around and letting things corrode worse than when we keep driving a car!

IF DIY, take the cover off the generator and there should be one big red battery cable from the batteries, that is often connected directly on the solenoid, so make sure it is clean there and the battery as a first look!
When looking and somebody else hits the start switch, you can hear or feel the solenoid click. that means the wiring from the switch to solenoid is working as the contacts are moving( clicking?) It CAN be a bad solenoid and maybe the contacts are closing but burned or worn too bad to pass the current!
But that solenoid is usually not too expensive and might be easy to change?
Maybe something like this model??
https://www.amazon.com/JZGRDN-307-25...zcF9hdGY&psc=1

[Mikeknapp]

Great suggestions.
I have the same Gen. Step 1, place a voltmeter between ground and directly to the starter connection on the gen. While cranking it should be 12.3VDC or better. Under 12 indicates high resistance in the cables or connectors (or maybe a bad start solenoid).
Step 2, I suggest taking a known good battery and a set of jumpers and with the RV chassis battery disconnected, clip negative to a clean spot on the gen, then tap the + of the battery to where the red cable connects to the starter on the gen.
If it cranks, you probably have high resistance in your cable connections (corrosion, loose, bad ground--remove all connections, sand till shiny, protect with silicone grease, and re attach).
Don't forget there are ground cables between the generator and the chassis, as it is usually rubber isolated. After that, if it still clicks, I would replace the solenoid first, then the starter.

[RV Tinker]

Had a similar problem with my generator. Starter would click, battery was good, solenoid was good, good connection to generator but would not turnover. Found out that problem was that there was a spot where the engine would stop rotating at where it could not turn over. Solution I found online was to manually rotate the engine using a wrench just a bit and it would now turn over. Strange but it worked.

[Rixthe1]

Replacing an expensive part, without diagnosing the failure, is rarely the best course of action. Charge up the batteries, I would put a socket and ratchet, on the crankshaft bolt, and see if it is locked up. Then I would hook up my jump box and see if it cranks over. If it does not, I would remove the starter, and have it tested.

[Four Seasons]

My money would be on the unsheathed cable between the solenoid and the starter motor. You could try to short the connection with a screwdriver, but if you're not comfortable with that, don't hesitate to take it to a Cummins/Onan dealer - they will tell you within a few minutes where the issue is.

[Tadrith Bear]

It was empty of oil, so i filled it. I hear solid clicks from the solenoid, and i hear a faint electrical buzzing when i hold start. In another set of troubleshooting suggestions, they recommended i try to remove the sparkplug and turn the flywheel by hand. I cannot move the flywheel by hand, nor with a wrench. I'm quite sure something in the system is stuck. I'll double check the voltage going to the starter, in case it's stuck engaged and is holding it locked up. But I'm looking into removing it to begin disassembly or replacement.

[Mikeknapp]

Oh my. No oil is not a good thing. Perhaps it was drained for long term storage, and now is just 'stuck' as you noted.

If a serious effort (like up to 100+ ftlb) attempting to turn it over with the flywheel bolt gets nowhere, it is starting to sound like it was run with no oil and is seized up.
The engine is not terribly complicated and if you can find parts and have ever overhauled a mower (or have a buddy who has), it is probably repairable for considerably less than a new generator. You will have to take it apart (this is the cheap part) to assess the final damage.
Good Luck!!

[tim myers]

I have also seen short blocks for these gensets under $1000, but then we need to make sure the power generation side is working also

[Ray,IN]

Before panicking and giving up on this genset; remove the spark plug and add a teaspoon of Liquid Wrench into the hole. This will hopefuly free-up stuck rings in the cylinder.
Next day wrench it hard enough to get a small amount of piston movement. Repeat every 4 hrs until you can turn the engine one full revolution.
Then use the starter to crank the engine without the plug installed..Once you accomplish that, replace the plug and attempt to start the engine.

[tim myers]

Originally Posted by Tadrith Bear

It was empty of oil, so i filled it. I hear solid clicks from the solenoid, and i hear a faint electrical buzzing when i hold start. In another set of troubleshooting suggestions, they recommended i try to remove the sparkplug and turn the flywheel by hand. I cannot move the flywheel by hand, nor with a wrench. I'm quite sure something in the system is stuck. I'll double check the voltage going to the starter, in case it's stuck engaged and is holding it locked up. But I'm looking into removing it to begin disassembly or replacement.

How are things progressing, any luck with the genset yet?

[Morich]

On the idea of the solenoid being stuck, I would think not as the clicking is the solenoid contacts closing?

When we hit the switch to start, it is a good sign to hear the click as that means we are hearing the contacts move toward closing. If they are corroded or damaged too much to pass the current on or if the engine is frozen we don't get cranking and as we let go of the switch they drop off again.
Point to keep in mind is that each time we try to start it heats the starter a bit and if done too much and too often it can fail! If the contacts stick full time, it will be a massive amount of power drawn and something will fail.
Either the batteries run fully down, the starter or wiring overheats or fuses blow.

[tim myers]

He has it removed from the chassis now, hopefully bench testing will reveal the issue. I personally feel it is just seized up/corroded from sitting, penetrating oil on the rings and time may get him to the point of getting it to turn over, then he will find out if it is dead or of the motor needs to be re-built or replaced

[Tadrith Bear]

Christmas break is coming up and i actually enjoy doing this stuff �� so I've set aside a few days to organize myself and disassemble as much as i have equipment for (which should be most of the gas side). Clean, inspect, repair/replace, reassemble.