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

[Grit_dog]

Sorry, off the OPs topic, but I wouldn’t un-recommend Stabil or any of the other gas stabilizers.
Another suggestion that works well for stabilizing or using small amounts of fuel in engines without catalyst emissions and 02 sensors is 100LL. It’s not much more $ than non ethanol premium and it does not need to be treated or drained for about 2 years.
It’s more highly refined than automobile fuel.
OP issue sounds like a voltage or sensor issue. I do not have any direct experience w Onanistic but the suggestions sound right.

[klutchdust]

klutchdust wrote:
Having been around diesel and gas engines for a lifetime I know this :

" 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"

This in my opinion is a terrible idea, to keep an engine running on starting fluid and here's why.

Do you notice that the engine chatters, clacks and everything else while using starting fluid/ether? Starting fluid puts engines under stress, it strips the cylinders of lubrication. Sure you can spray a little if you like, it's your engine however I have not purchased or used any in my engines ever since I saw a mechanic use it, walk away then another mechanic came along and not knowing ether was sprayed - hit the glow plug button on the diesel tractor and the explosion removed the head gaskets from the block.

Also, I am very disappointed in Sta-bil fuel additive. I have used it and still have had issues with my small engines, the ones I cannot run out of fuel before storing. Now, a product called "mechanic in a bottle" used it, it works, I recommend it to friends with no mechanical ability for their mowers etc.
so I am not asked to do a carb rebuild .....:C

[klutchdust]

Having been around diesel and gas engines for a lifetime I know this :

" 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"

This in my opinion is a terrible idea, to keep an engine running on starting fluid and here's why.

Do you notice that the engine chatters, clacks and everything else while using starting fluid/ether? Starting fluid puts engines under stress, it strips the cylinders of lubrication. Sure you can spray a little if you like, it's your engine however I have not purchased or used any in my engines ever since I saw a mechanic use it, walk away then another mechanic came along and not knowing ether was sprayed - hit the glow plug button on the diesel tractor and the explosion removed the head gaskets from the block.

[ron_dittmer]

bobndot wrote:
I remember my dad using white gas for our camp stove and its shelf life was great.

"Great" is an understatement.

My parents had old Colman fuel laying around as did my siblings. They knew we camped with a camp stove (until 2007) and gave us their old fuel. After we bought our motorhome, we had no need for that fuel. Still I kept it for years longer just in-case, and I still have one gallon today. After all those years it still remains clear as water and smells like new so I put most of it to good use in my car's fuel tank.

White gas used in camp stoves and lanterns is unleaded fuel without additives including cleaners and pollution retardants. It is as pure of an automobile fuel as you can buy, though I wouldn't recommend driving around in tank fulls of it.

[JaxDad]

Dutch_12078 wrote:

Kennyg wrote:

Dutch_12078 wrote:
Does the generator keep running if you hold down the start switch? If it does, that indicates that it's not putting out enough voltage to the control board to lock in the run cycle. It could be a faulty voltage regulator ($$$), or it could be dirty slip rings. Holding the start button down for a minute or two may clean the rings enough to keep it running. Worth a try anyway...

No. will run ,but as soon as I release button, the engine stops.

Does it keep running as long as you hold the button down? Even for a minute or longer? If it does, it's not an engine problem, it's an electrical problem...

Indeed! Older 4K units employed a very rudimentary ’safety’ system since they operated on a ‘power in / power out’ basis’. 12 volts = 120 volts out. The problem is that the genny would start on 8 or 9 volts, but 80 or 90 volts out would let release the magic smoke from things. The simple solution was a voltage sensor, much less than 12 volts meant the engine shut off. This of course is bypassed as long as you hold the start button.

Even a nothing booster pack will keep it up long enough for the battery to recover or charging to kick in.

On a few occasions I’ve stood holding the button for a few minutes.

[Dutch_12078]

Kennyg wrote:

Dutch_12078 wrote:
Does the generator keep running if you hold down the start switch? If it does, that indicates that it's not putting out enough voltage to the control board to lock in the run cycle. It could be a faulty voltage regulator ($$$), or it could be dirty slip rings. Holding the start button down for a minute or two may clean the rings enough to keep it running. Worth a try anyway...

No. will run ,but as soon as I release button, the engine stops.

Does it keep running as long as you hold the button down? Even for a minute or longer? If it does, it's not an engine problem, it's an electrical problem...

[wopachop]

I think many RV people would benefit knowing you can easily drain the carb. Look for a little screw on the float bowl.

[bobndot]

wopachop, I remember my dad using white gas for our camp stove and its shelf life was great.
Doing what you mentioned using Coleman fuel would probably work for storing a generator during the non-use months due its long shelf life. You would not need to stabilize it. Getting that fuel into the and thru the carb and lines, I think would be good for a very long time. Others in the rv crowd talk about doing that.

[wopachop]

I wonder if you could:
1. Measure and monitor voltage to the solenoid as you press and release the start button.

2. Use a battery and alligator clips to give the solenoid 12v directly.

I always recommend using an empty water bottle and short piece of fuel line to gravity feed fresh gas directly to the carb. This eliminates fuel pump, fuel filters, fuel line, old gasoline.

Also allows you to feed a very strong mixture of carb cleaner into the carb if you suspect old gas has gummed up the jets. I have fixed clogged up Onan carbs many times using that method. It's not ideal. But it's quick and easy and cheap.

[bobndot]

https://www.irv2.com/forums/f54/onan-gas-generator-fuel-cutoff-solenoid-456887.html

[Kennyg]

Dutch_12078 wrote:
Does the generator keep running if you hold down the start switch? If it does, that indicates that it's not putting out enough voltage to the control board to lock in the run cycle. It could be a faulty voltage regulator ($$$), or it could be dirty slip rings. Holding the start button down for a minute or two may clean the rings enough to keep it running. Worth a try anyway...

No. will run ,but as soon as I release button, the engine stops.

[Kennyg]

wopachop wrote:
Does your float bowl have a drain on the bottom?

YES - Have drained it number of times and very little comes out. Finally, I have pulled gas line and hit start button and definate volume of gas is being seny to input of bowl .

Can someone explain the purpose of the solenoid on carb?

[Dutch_12078]

Does the generator keep running if you hold down the start switch? If it does, that indicates that it's not putting out enough voltage to the control board to lock in the run cycle. It could be a faulty voltage regulator ($$$), or it could be dirty slip rings. Holding the start button down for a minute or two may clean the rings enough to keep it running. Worth a try anyway...

[wopachop]

Does your float bowl have a drain on the bottom?

[ron_dittmer]

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

I lean towards this too.

So many people go right to the carburetor when there is a problem. There are countless replies over the past 14 years I have been hanging out on RV forums, people saying "It's Your Carb", "Use Seafoam", Replace Your Carb".

For the past 32 years, I have been living in a house on an acre so I have a 18hp lawn tractor, 8hp roto-tiller, 8hp snow blower, and a 5hp power-washer, all of which are 4 cycle engines with simple carburetors. The tractor, tiller and snow blower are 32 years old. When I am done with any such equipment for the season, I simply place them aside. I don't do any storage preparation what-so-ever including never adding a fuel stabilizer. When I pull them out to use them as needed, I check the oil level or change the engine oil if it's time, and clean or change the air filter. I top off the fuel tank and they initially start rough, but after a minute, they smooth out and are ready to get work done. For the past 14 years, I have always applied the same practice to our Onan, yielding the same good results as my yard equipment.

Due to becoming "involved" grand parents along with world travel, this past summer marked a two year period since I previously started our motor home or our Onan. Two years was the longest duration yet so I was a tad bit concerned. The motorhome is stored indoors so I was fairly confident all would be well and I was right. The Ford V10 engine started instantly and smoothly as if I had it running an hour earlier. With a lot of priming in advance, the Onan started up fairly quickly, and behaved as it always did, requiring a minute or so to smooth out.

This past summer during that awakening, after 20 minutes of running properly under load running the a/c unit, my Onan suddenly shut off. After some research, I narrowed the problem down to the fuel pump. It became sensitive to working when it is very hot outside. When the day cooled off, the fuel pump worked fine. I have a new fuel pump and filter ready to install prior to our next trip.

I think much of the reason why Onan recommends running the generator once a month is because some are stored outdoors in very high humid environments. Running it as recommended might be for the sake of the power generating portion of the unit, not the engine itself.

As far as a "gummed-up" carburetor is concerned. Today's fuels are formulated to avoid that varnish that we dealt with in the days with carbureted automobiles. Vehicles today with high pressure fuel injection systems cannot tolerate "varnish" and such, so the fuel is so much cleaner than years ago. This "clean" fuel benefits small engine carburetors. There is no varnish build-up. There could be dirt build-up from a leaking air filter, so carb cleaners like Seafoam does have it's use. 2-cycle engines with oil in the fuel benefit greatly from carburetor cleaner products.

In many parts of the USA, fuels include a certain amount of alcohol. That cleans things better yet leaving even less residue in the carb as it evaporates away during the storage period, but the additive is hard on rubber gaskets and seals and such in many carburetors. It tends to dry them out, stiffening them, and in a worst case scenario, it cracks the rubber seals. My 1983 Toyota pickup truck I owned for 24 years, had a diaphragm in the side of the carb that the alcohol would dry up to the point that it no longer would move as it was supposed to. I had to change that part every-other year because of the alcohol in the fuel. Around these parts, I cannot buy gas without some amount of alcohol.