Help! Onan 4K generator refuses to start and stay on

[Kennyg]

Pulled RV out of 6 month storage. Attempted to start generator. Will start, but quit after about 6 seconds. Repeated attempts with no success.

When it does start, it runs only briefly. It seems to me that it is not getting a constant flow of gas. Should I empty the "float bowl" to get clean gas ( no I didn't drain the bowl before placing unit into storage) and then attempt to start again.

The fault light indicates a fault 36. This fault seems to imply I should either clean or replace the spark plug.

Any and all advise will be greatly appreciated

[whemme]

My vote is that you have a weak/inoperative electric fuel pump on your Onan generator

[Kennyg]

Well, thanks for all of the advise. Will try all of the suggestions in next few days. Need to watch the packers first!!

[pconroy328]

Kennyg wrote:
Pulled RV out of 6 month storage.

I suspect I know the answer, but -- did you run the generator, under load, for 45-60 minutes every month??? Like the manual says? 🙂

If not, then I'll also vote for a carb problem.

A new carb at an Onan dealer will run you $750. I know this from personal experience. Others have had some success by seafoaming, stabil-izing the snot out of the carb.

Maybe 70% of the problems I've followed over the years were carb. The second most popular were fuel pump for the Onan 4K.

[bobndot]

Blue smoke could be an overfilled oil res.

I copied the following from another rv tech post onan 4000

The carb on 4KY has a seal washer on INSIDE of float bowl, where fuel solenoid fitting comes through hole in bottom of bowl. If you have bowl off carb., and are not careful, or don't know this washer is there, it is easy to lose it.Then carb will not work correctly, will overfuel, etc. Might be something to check out. (been Onan tech 20+ years)

Another problem could be the fuel pump.

[ron_dittmer]

Hi Kennyg,

I would try this.

- take off the air filter
- start the generator
- as it starts to die on you, spray a little starting fluid in the carb to keep it running
- keep doing it until you are tired of doing so

Just maybe running the generator for a while that way will clear up the cause

If you can keep it running with the starting fluid, but the engine refuses to run on it's own, then check fuel flow. Disconnect the fuel line and run the fuel pump with the start button in the prime position. If it stops at the same 6 second interval, then it sounds like a problem with your fuel pump.

If you cannot keep the generator running with squirts of starting fluid, then you have an electrical problem, not a fuel problem.

[Kennyg]

Well, I dissembled the carb, cleaned it with carb cleaner and reassembled. Now, it runs for short time, very ragged and then quits, But, now the exhaust is BLUE whereas before the clean out it was almost clear. So, I need some suggestions. Do I really need to replace the entire carb/ Last question, what is the purpose of the solenoid and its purpose? Thanks for all your advise to date!

[azdryheat]

My genny did the same thing, start for a short period and stop. Cleaned out the carb and all is well. It's really very easy.

[whemme]

Disconnect the fuel hose between the output of the generator’s electric fuel pump leading to the carburetor. Then hold down on the generator’s STOP button. This should turn on the fuel pump’s priming function and cause fuel to run out of the pump. No fuel - probably a bad fuel pump.

[wopachop]

Kennyg wrote:
When it does start, it runs only briefly. It seems to me that it is not getting a constant flow of gas. Should I empty the "float bowl" to get clean gas

It could answer questions quickly. Be ready with the screwdriver and next time the genny dies crack open the float drain and see how much gas comes out.

If a lot of yellow looking gas comes out of the carb. Then it would be safe to assume you are getting enough gas to the carb. Mostly likely the problem is old gas, not lack of gas.

You can prime the system, crack the drain, and see how much gas comes out to get a feel for how much gas in is a full float bowl.

[Dusty_R]

We had an 01 Itasca MH. I added a switch to the generator fuel pump, and when I knew that we were not going to use it again for a while, I would turn the switch off and let the generator run out of gas.

[cencerrita]

jdc1 wrote:

Kennyg wrote:

jdc1 wrote:
Time to clean the carb.....

Carb is only 2yrs old. Do you mean removing and cleaning??

Old gas gums up carburetors. It's the largest issue with small motors, including older motorcycles.

Onan say you can not strip and clean their carbs - wrong! They are quite simple and compared to about $400 for new one worth doing!
There are photos of doing this in the book, Owners Essential RV Handbook

Unfortunatly I do not have any on this computer from when I did mine having forgotten the previous trip to drain my carb or run the fuel through with the fuel treatment I had added to the tank before storing. Previously having done this I stored for up to 6 months no problem compared to Onan saying you should "exercise" your onan every month to stop the problem.

[jdc1]

Dusty R wrote:
Check to see if the electric fuel pump is working.

If you find the fuel pump isn't working, you can buy an off-the-shelf low psi fuel pump from any auto parts store. They are about $20.00, 1/4 the price of an Onan part.

[jdc1]

Kennyg wrote:

jdc1 wrote:
Time to clean the carb.....

Carb is only 2yrs old. Do you mean removing and cleaning??

Old gas gums up carburetors. It's the largest issue with small motors, including older motorcycles.

[Dusty_R]

Check to see if the electric fuel pump is working.

[Gjac]

2naEagle wrote:
Found this video. I haven't done this but looks like it would work.

Can & Hose Method

This is what I do when ever I have a problem starting or keeping the genset running. It also shows you if the problem is a loose hose clamp or a cracked fuel line to the main tank drawing air in instead of enough fuel to keep it running. With the other half of the Seafoam I put it into the crankcase before I drain the oil. You would be surprised at the carbon that comes out of the sump if you never did this before. It also shows you how much fuel you burn in an Hr under load.