onan 4k is "hunting"

[Kennyg]

Some advise needed here. A 2007 4k model hard to start, probably because it was not maintained properly. Any way, does the problem reside in the status of the carb. or in the plug or both? Plus,the exhaust enters the unit every time the unit is running!

[Kennyg]

Thanks to all for the advise, unit presently is in storage, but will do work in late august before going south. Thanks to all for the advise.

[Scrooge39]

A short time ago I downsized my motorhome and the shorter one had an Onan 4K generator in it. Finally got around to running the generator but it would only run 5-10 seconds then stop with a code of 14 (high frequency). Went online and a majority of the hits pointed to carb problems as the engine was “hunting”.
Another “fix” was to drain about a cup of oil out of the crankcase. Being the eternal skeptic, I muttered under my breath “riiiiiiight”. I replaced the “usual suspects” (air & fuel filter) but that did not solve the problem. Thought about the oil fix and decided I had nothing to lose and it didn’t cost a thing. I drained about a cup of oil and fired up the generator. It ran continuously;let it run for app. a half hour with various loads and it never skipped a beat.
Did more research and found out this model generator has a low oil-level sensor. It seems if the oil level is high (not necessarily over-full), it causes the Onan “brain” to do some odd things.
This fix worked for me, you might give it a try. As I mentioned above, it’s free and I had nothing to lose.

[PaulJ2]

Since emission controls and all, every small engine now is adjusted to the ragged edge of lean. Therefore any little partical of dirt in a jet or port causes a lean condition and hunting.

[Kpackpackkelley]

To much fuel or to little can cause hunting. Has anybody tried adjusting the main jet before ? There’s a blue paint mark on the main jet let us know what position it’s at.

[theoldwizard1]

DrewE wrote:
You might check that the choke linkage is working properly and the governor linkages are not gummed up, but there's a good chance that the carb itself needs cleaning ...

Check, yes. Adjust, NO !!!

DrewE wrote:
These engines are pretty standard small air-cooled engines, and basic troubleshooting isn't different than for e.g. a lawn mower engine.

True ! And the most common problem with a carbureted small engines that are hunting/surging is a clogged idle/primary jet. This can be a DIY job if you like to do things yourself. A dealer will charge over $100 maybe more depending on how hard it is to get the carburetor off.

I have had very little success with SeaFoam or other additives for this type of problem.

[Chris_Bryant]

Try both Seafoam and Berryman B 12. I take the fuel line off and run a short piece in to a gas can super treated with one of these. Run it for a bit, shut down and let it soak overnight.

[Dennis12]

I had the same problem with mine. 13 HRS on it. I took it to Onan and they did carb cleaning, checking and adjusting. works fine now

[ksg5000]

Use the forum search feature using the words Seafoam and Generator --- lots of threads that should help resolve your problem.

[DrewE]

Hunting and hard starting are more typical of carb problems than a bad plug. A bad plug would make for hard starting (or no starting), to be sure, but once running should not cause hunting. You might check that the choke linkage is working properly and the governor linkages are not gummed up, but there's a good chance that the carb itself needs cleaning or replacement. (Also check that the altitude setting is correct for your location.)

These engines are pretty standard small air-cooled engines, and basic troubleshooting isn't different than for e.g. a lawn mower engine.

Exhaust getting into the RV is a serious problem, possibly caused by a faulty muffler/exhaust pipe, and possibly by an improper installation, a silly positioning of a window or something, or trouble with sealing the motorhome. It should not take a rocket scientist to track down what's happening there. Correct that as soon as practical. A GenTuri (or homemade equivalent) may be an excellent idea even if you find something that needs fixing to get the exhaust fumes up above the RV.

My generator generally hunts for the first minute or two if it hasn't been run recently due to the fuel line having a couple air bubbles in it. Many of the 4KY variants can be primed by holding the control switch in the off position before starting to avoid this, but unfortunately not mine. This just runs the fuel pump without cranking the engine; it may take something like 20 or 30 seconds to fully prime. Generally you can hear a change in the pump's noise when it's set to go.