Onan generator

The place to go for Onan trouble shooting is here:

https://www.smokstak.com/forum/forumdisplay.php?f=1

They also have factory service manuals for your models, which include diagnostic procedures.

I'm in the middle of fighting with my Onan and have been for months. This week I'm pulling the voltage regulator and control board (both Flight Systems replacements replaced in 2009) and sending them in for testing ($35 each which they refund if you buy a new board).

Steve

Here's some stuff you can do in half an hour with absolutely no training. They have nothing to do with the fault code; they are general tests for a novice. They will cost very little money and time.

• Fill the tank with more gas. Consider adding whatever fuel additive you find at the gas station: Seafoam, Stabil, Techron. Follow the directions on the bottle that you get. I'm recommending an additive because it can almost never hurt and it sounds like your generator might need some TLC, and a basic fuel additive is a very easy and simple way to provide a small amount of help.
• Check the air filter by taking to cover off the generator, locating the boxy metal housing in the top left, unscrewing the wingnut on the far left of that housing, removing the metal cover, and pulling out the air filter. It should look cleanish and whitish.
• Check the oil by removing the yellow oil cap in the bottom right of the generator. The oil should be between the correct lines on the dipstick (which is attached to the cap itself). If you want to change the oil, it's almost identical to doing so in a car, except you remove a small plate on the underside of the generator (two Torx screws) and then remove the large hex bolt revealed by the removal of the plate. This will drain the oil.
• Check the governor linkage (to the throttle) and the choke linkage (to the choke). These are the two long bars attached to spring-loaded clip looking things on top of the carburetor (which is the complicated silver thing directly in the center, to the right of the air filter housing and to the upper left of the oil cap). When you grasp and move these linkages back and forth, they should move freely and smoothly, returning easily to their original position.

If none of these quick interventions show something obviously amiss (low fuel, bad filter, low or bad oil, stuck linkages), you will either need to learn how to troubleshoot more complicated problems yourself OR take it to your local Cummins Onan shop.

Cummins service comes at a premium. Expect two hours of labor at $140/hr just to diagnose your problem. However, the technicians should be honest, communicative, and helpful, as is the Cummins reputation.

An intelligent and wrench-experienced person should be able to replace a fuel pump, fuel filter, carburetor, control board, voltage regulator, air filter, throttle or choke linkage, fuel line, carburetor gasket, governor spring or linkage spring, or starting solenoid on his or her own without much trouble. (Not saying all those things could be the problem, but that's a good start for things you can fix on the ground in front of your generator.) Many other things require you to "drop" the generator off the motorhome; you would need a transmission jack or similar floor jack and a whole bunch of PB Blaster and wrenching on the retaining bolts. Most people have Cummins perform that kind of work, because it is an Enormous Pain in the Butt.

Your generator is a 4KY Spec K. Parts, service, and operator manuals can all be found on the internet or bought for $15-20 online. I just fixed a 4KY Spec H and would be happy to help you out. Do everything listed here and report back.

Also, it's my understanding that the Slip Stick will not work on 4KY models, because the slip rings are not visible to the eye behind an accessible vent. I could be wrong.

bobsallyh wrote:
I just wish Kubota, Yamaha, or Honda would make direct replacements for Onan RV gennys. Onans are like an old woman, needs a lot of TLC!

I second that! Up to about 10 years or so ago Honda offered the 4,000 VA EV4010 and 6,000 VA EV6010 RV generators that I vaguely remember fit into the same physical space as the Onans. They were still 3,600 rpm constant speed devices, but were twin cylinder and liquid cooled, which I expect would lead to smoother and quieter operation. I guess there's just not enough volume in RV generators for more than one vendor. I think Generac is out of the market, too. In addition to microquiet clones, they had a couple of variable speed inverter models that looked pretty good in terms of specs and features, but had reliability and support issues (based on what I've read). I think an rv-repackaged eu3000i would be pretty darn popular.

road-runner wrote:

bobsallyh wrote:
I just wish Kubota, Yamaha, or Honda would make direct replacements for Onan RV gennys. Onans are like an old woman, needs a lot of TLC!

I second that! Up to about 10 years or so ago Honda offered the 4,000 VA EV4010 and 6,000 VA EV6010 RV generators that I vaguely remember fit into the same physical space as the Onans. They were still 3,600 rpm constant speed devices, but were twin cylinder and liquid cooled, which I expect would lead to smoother and quieter operation. I guess there's just not enough volume in RV generators for more than one vendor. I think Generac is out of the market, too. In addition to microquiet clones, they had a couple of variable speed inverter models that looked pretty good in terms of specs and features, but had reliability and support issues (based on what I've read). I think an rv-repackaged eu3000i would be pretty darn popular.

I'm going to THIRD this! Our 99 Xplorer has a 2.8 Onan, it always cranks, but sometimes it doesn't start. Sometimes, it does. Once it started, but would not generate power. Sometimes, it runs smooth, sometimes it surges. I'm tired of the inconsistency and noise. Why hasn't someone used the new inverter technology from the portables for a built-in on-board genny?

Gerard

We can only hope for an Onan replacement....SOON ! I had a liquid cooled Honda in my GMC motorhome, it seemed to be a much less irritating sound than the Onan...and it was dependable. Shoulda kept it, the generator was worth more than the MH.

Wonder how tall a Champion 3400 would be if you took the handles & Fuel tank off the top? Not concerned about warranty issues, nor closing the top of the case. Just looking for a inverter type replacement that will fit.

somebody needs to burn this thread
never found out the initial problem and now we're talking about a portable generator

It is inevitable when the following are coupled

Minimal mechanical diagnostic aptitude
No diagnostic tools

Failure to remain in contact with the forum
Failure of forum members to utilize self-control and help the OP focus and stay focused.

The OP will become overwhelmed and submerge.

After struggling with my 4BGE Spec G generator off and on for a year, I also considered putting one of those cheap import generators in place of my Onan.

Then I watched the 24 hour torture test between an ancient Onan that looked like it had been pulled out of a swamp and a brand new Champion. Champion went about 25 hours before the engine destroyed itself.

If you are not experienced with generators, it can seem like a mysterious "black box". They really aren't so complicated.

The Onan motors are pretty bullet proof. As long as you don't run them out of oil, the mechanical portion of your generator will probably never give you any problems.

Thus the problems are either going to be electrical or carburetor related.

Onan service manuals provide detailed information on how to rebuild carburetors. They can be tricky to work on as there are some tiny, fragile parts. Or, you can just replace the carb for about $300 if you do it yourself, depending on your genny.

The starter is easy to replace and cheap if you go aftermarket.

The coil is easy to replace and cheap if you go aftermarket.

The ignition control module can be pricey but is easy to replace.

The control board is pricey but easy to replace.

The voltage regulator is pricey but easy to replace.

On my Onan 4BGE, you can replace the entire ignition electrical system and the starter for about $200 if you do the work yourself. Much less hassle than trouble shooting.

The key to these things, as has already been noted, is you have to run them. You need to run them monthly under load for two major reasons: First, you need to keep fresh gas running through the carb, with vibrations and heat working to get rid of gum buildup in the carb. Second, it keeps the slip rings clean. If they get get dirty, then the resistance between the brushes increases. This can damage the voltage regulator, which is a $200+ component on my genny.

If you're not willing to tackle your generator, you can pretty much count on spending at least $500 the minute you drive it into a shop.

Steve