Generator dies when load removed

[bruceh]

I am having a weird problem with my Marquis Gold 5500. When I exercize it with the AC it runs fine. When I turn the AC off, the generator stops. I can restart it and it runs fine.

It just came out of the Cummins shop after having the drive belt replaced. I will not be going back to that shop, I don't want to see them and they don't want to see me.

Any suggestions that don't require a trip to Cummins.

[donr103]

When is last time you cleaned armature slip rings ? How many hrs ? Does yours displays codes?
Good luck and keep us posted

[DFord]

The generator will shut down if the frequency (Hz) gets too high. The frequency is dependent on the speed of the generator. When you remove the load from the air conditioners, the generator may be speeding up just enough to trigger the controller to shut it down. There will a be a flash code on the switch on the generator if that happens. Compare the flashes with the troubleshooting chart in the manual.

[twinboat]

Your age generator may not have flash codes to help troubleshoot.

Pickup a Kill A Watt meter so you can check voltage and Htz.

Plug it in and see if the voltage and Htz are in range, it may be a bit high and lowering the RPMs will fix that.

[Isaac-1]

My guess is either governor out of adjustment, or carburetor issues, there is a specific sequence of steps you should follow to adjust the governor, letting some idiot with a screw driver get in there and start adjusting things until it "seems to run better" is a great way to get into your current situation, where it may run at the correct speed until a heavy load is either applied or dumped.

[Randalpho]

I had to readjust the throttle hard stop on mine for the same shutdown issue after turning off the load.

https://www.irv2.com/forums/f54/onan...ml#post2481954

[shootist]

This is general gasoline engine knowledge, apart from control electronics from the generator. When compression gets weak by valve leakage engines will die returning to idle. The cause is simply not enough air passing through the carb to draw the required fuel into the mix. Putting on a smaller carb used to be an old trick to keep a car from dying at every stop sign.
So in regards to your problem, do a compression check , if it's good focus on the carburetor. Slightly plugged idle and or emulsion tubes is where I would look. Common for those two things to varnish up in equipment that sits. Also use spray carb cleaner and clear all the air bleeds/passages. For some of these engines new carbs are amazingly reasonable in price. I would not go with a chinese knockoff, however most Cummins stuff has been chinese for a long time. It makes it hard to pin down the oem supplier.
A quick search shows a subaru engine fitting onans description and specs. It has a vacuum choke so look for cracked or fallen off vacuum lines. The fuel pump could be failing or clogged lines but unlikely.

https://subarupower.com/products/eng...v-twin-engine/

That may be your motor?

[bruceh]

Originally Posted by Randalpho

I had to readjust the throttle hard stop on mine for the same shutdown issue after turning off the load.

https://www.irv2.com/forums/f54/onan...ml#post2481954

This is most helpful and matches my symptoms exactly.

Can this adjustment be done without removing the genset from the RV?

[Randalpho]

Originally Posted by bruceh

Can this adjustment be done without removing the genset from the RV?

Yes, and with the genset not running.

You can count the turns (1/8, 1/4, or two full turns in my case) on yours as you back off the stop screw.

After I readjusted it the white paint marks on mine lined up again. This confirmed my suspicion that somebody messed with the adjustment.

2. Loosen the throttle stop screw locknut and
back the screw out away from the tang on the
throttle lever, while gently rotating the throttle
lever counterclockwise as far as if will go.

3. While gently holding the throttle lever counterclockwise
as far as it will go, turn the stop screw
in until it just touches the tang. Then turn the
screw an additional 1/8-1/4 turn (clockwise)
and set and seal the locknut.

[bruceh]

Marquis Gold 5500?

Mine looks like this.

[Randalpho]

What is your model number? Mine is a 5.5BGM

You list a 2001 and a 2007 in your signature.

[bruceh]

I have two, the one that I am working on is the 2001

This is the model of genset.

Since I got a way to measure frequency, I have a better understanding of the failure.

With no load, the frequency gradually rises to 66 Hz and code 14

Under load (AC full blast), the generator keeps running at 63Hz.

When the load is removed, speeds up and code 14.

[Randalpho]

Your model is different than mine even though it's one year apart. Per the manual it states for code 14 to take it to the dealer. Sorry I don't have better info for you.

OVERFREQUENCY FAULT—CODE NO. 14
(Engine governor unable to maintain rated frequency)
Corrective Action: See an authorized Onan dealer.

https://www.cummins.com/sites/defaul.../0983-0101.pdf

Maybe this would help?

https://www.flightsystems.com/pdf/on...ting-guide.pdf

[Ray,IN]

I would guess a dirty, sticking governor.