Onan 5500 Problems

[TerribleTim68]

Hey guys,
Figured I'd better fire up the generator before our big outing this week. Wouldn't you know it, it won't run.

I put fuel in the tank until it was about 3/4 full. I read somewhere that the generator won't run if it is below 1/4 tank, so that was the first move. So she's got fuel in the tank.
I pulled the fuel line off at the carb and it will pump fuel out the end if I hold the "Prime" button down. So fuel is coming out of the end of the line.
I read that these carbs can be notorious for getting gunked up, so I pulled it off, took the filter off, removed the small elbow at the filter, took the float bowl off and emptied an entire can of carb cleaner on the thing trying to un-gunk it. I also assured that the fuel filter was clean by blowing through it, it flows very easy and you can blow through it with no pressure at all. Then I put the carb back together and put the happy little clam back on the generator.

So here's where I am. I can get fuel to pump out the end of the line using the "Prime" button. It's not a lot, but it's flowing. I don't know how "fast" it should pump. If I hook the fuel line up to the carb, open the little screw at the bottom of the fuel bowl and hold the "Prime" button, it will not flow fuel out of the bottom of the bowl. It is like it is simply NOT filling the float bowl with fuel. Now, I'm not a certified mechanic, but I know my way around a small block Chevy. Using my limited mental abilities, my assessment is that the little needle that open the float bowl inlet is simply stuck. I have no clue how to pull that apart to un-stuck it. I tried the "beat on the side of the bowl with a wrench" trick, to no avail. Is there a way to get at that, or is that one of those "just buy a new carb" deals? I see there are no replacement parts for these carbs, just just have to replace the whole **** thing. Is that were I am here?

Also, I can make the generator run fine on starter fluid, so I know it will run.

 

[Chrisandsama]

Hey guys,
Figured I'd better fire up the generator before our big outing this week. Wouldn't you know it, it won't run.

I put fuel in the tank until it was about 3/4 full. I read somewhere that the generator won't run if it is below 1/4 tank, so that was the first move. So she's got fuel in the tank.
I pulled the fuel line off at the carb and it will pump fuel out the end if I hold the "Prime" button down. So fuel is coming out of the end of the line.
I read that these carbs can be notorious for getting gunked up, so I pulled it off, took the filter off, removed the small elbow at the filter, took the float bowl off and emptied an entire can of carb cleaner on the thing trying to un-gunk it. I also assured that the fuel filter was clean by blowing through it, it flows very easy and you can blow through it with no pressure at all. Then I put the carb back together and put the happy little clam back on the generator.

So here's where I am. I can get fuel to pump out the end of the line using the "Prime" button. It's not a lot, but it's flowing. I don't know how "fast" it should pump. If I hook the fuel line up to the carb, open the little screw at the bottom of the fuel bowl and hold the "Prime" button, it will not flow fuel out of the bottom of the bowl. It is like it is simply NOT filling the float bowl with fuel. Now, I'm not a certified mechanic, but I know my way around a small block Chevy. Using my limited mental abilities, my assessment is that the little needle that open the float bowl inlet is simply stuck. I have no clue how to pull that apart to un-stuck it. I tried the "beat on the side of the bowl with a wrench" trick, to no avail. Is there a way to get at that, or is that one of those "just buy a new carb" deals? I see there are no replacement parts for these carbs, just just have to replace the whole **** thing. Is that were I am here?

Also, I can make the generator run fine on starter fluid, so I know it will run.

You were almost to the needle with the bowl off of the carb, there's a small rod that holds the float onto the carb body, you pull that rod/pin and the float comes off with the needle. Clean and reassemble.

 

[TerribleTim68]

Thanks Chrisandsama,
So I finally got it to fill the float bowl with fuel, but it still won't run. I can verify that the "Prmie" button is pumping fuel into the bowl and out the bottom screw at the little drain. So the bowl is full. But it still won't run. I can still make it run for a bit off starting fluid, but as soon as that runs out, it dies. I'm guessing the jets are gunked up? Can those be cleaned? I can't even figure out where they are hiding.

 

[Chrisandsama]

The main jet is in the center of the carb. With the bowl removed you can see it, the float is surrounding it. A small flat tip screw driver will unscrew it from the carb for cleaning. Was the bowl full of gunk when first removed? If so the jet probably is also. It should run once cleaned.

 

[TerribleTim68]

Yeah, the bowl was stained green on the inside and the fuel was also kind of green colored. Not sure if it had some odd fuel stabilizer that tinted it green, or if it was some sort of algae growing in it.

The wife pulled rank and ordered a new carb off Amazon, so we'll see what happens when that arrives Tuesday.

 

[Chrisandsama]

Yeah, the bowl was stained green on the inside and the fuel was also kind of green colored. Not sure if it had some odd fuel stabilizer that tinted it green, or if it was some sort of algae growing in it.

The wife pulled rank and ordered a new carb off Amazon, so we'll see what happens when that arrives Tuesday.

The cheap Chinese carbs off Amazon and eBay are a roll of the dice I've gotten good ones and bad ones. Im a small engine mechanic and hopefully it gets you up and going.

 

[RickL]

Just remember it takes 3 things for a normal aspirated gas engine to run - fuel, compression, and spark. That being said my guess is you have compression so that leaves fuel and spark. So it’s easy to check spark so I’d go there next.

You’re probably on the right track being a fuel issue. The problem with the fuel today is left for 2-3 months (could in some instances be even a shorter period) is it “gunks” up the carburetors internal circuits. Not being there when you say the generator isn’t starting is it firing or just cranking over with no hint of fire? If it’s just cranking I’d try spraying ether or carb cleaner into the air filter and see it will try to start. It it starts to “fire” then in my opinion you probably have an internal carb issue. Not knowing these generators is there a electronic fuel shut off?

On most of the small engine carbs I have worked is the circuits internally are so small that about the only way to clean them is to remove the welch plugs but finding replacements are next to impossible so replacing the carb is the answer.

 

[LBR]

Go to YouTube and enter Seafoam Onan Generator and follow the instructions.

I bought our next to dead generator back to life with a little bit of nurturing.

It show how to rejuvenate a completely dead genny by mainlining the carb with Seafoam.

Wished I owned stock in that company....dozens of stories on small engine rehabilitations.

 

[TerribleTim68]

Just remember it takes 3 things for a normal aspirated gas engine to run - fuel, compression, and spark. That being said my guess is you have compression so that leaves fuel and spark. So it’s easy to check spark so I’d go there next.

Yup, I know it has spark because like I said below, I can make it run on starter fluid just fine. But as soon as the starter fluid runs out, she dies.
And I know I'm getting fuel in the float bowl too. I verified that by pulling the bowl off, hooking the fuel line up and running the "Prime" pump while watching fuel pump out the bottom of the carb where the bowl would be.
So, by my calculations, the issue is in the jets.

 

[Fourfunstuff]

These models are notorious for junking the carbs in the off season, that is how I got mine. My buddy replaced the carb EVERY year for four years and decided to by a portable gen set. I converted the free Onan 5500 to propane (300.00 kit) 5 years ago and have had zero issues since. the carb on your ONAN is not rebuild-able and is expensive to buy, but if you have no other choice I would buy an OEM and take the hit financially instead of eating up you time.


Good Luck

 

[TerribleTim68]

... I converted the free Onan 5500 to propane (300.00 kit) 5 years ago and have had zero issues since. ...


Good Luck

What's the process on that? Does it now run off the same bottles as the fridge/oven?

 

[Fourfunstuff]

Yes it will run off your service propane. I did have to modify the cover and space it 1 inch out from the original location to accommodate the spacer installed between the carb and air cleaner.

Here is the link for the kit:
https://centuryfuelproducts.com/generators/conversion-kits

Looks to cost about $200.00 now

If you decide to go this way and would like to see a video or pictures of the housing mod, let me know.

 

[TerribleTim68]

...If you decide to go this way and would like to see a video or pictures of the housing mod, let me know.

Yeah, I'd love to see some pics of the housing mod, just as general FYI.

 

[avvidclif]

If you are considering propane look at this chart. Two 30 lb bottles is less than 14 gallons.

No load - 0.4 Gal/h (1.8 lb/h) 0.8 kg/h
Half load - 0.8 Gal/h (3.3 lb/h) 1.5 kg/h
Full load - 1.1 Gal/h (4.6 lb/h) 2.1 kg/h

That's why I run my genny every month and religiously add fuel stabilizer, also Sea-Foam every so often. With 30 gal (rv tank) of gas I can get over 50 hours of continuous use. Most of the time I only need 1 AC but I have gone over 30 hours running 2 15k AC's without running out.

 

[jeffdee]

I have a 2014 3110 that is 6 years old this Thursday, August 1st. Since taking delivery, I have only put non ethanol regular or premium gasoline in the fuel cell. Every July, I empty the contents of the fuel cell and refill with fresh non ethanol regular gasoline. I have never had a problem with the fueling station pump nor running the generator. Also, I burn only non ethanol fuel in my ZTR that comes from my toy hauler. 10% ethanol fuels will ONLY work in automobiles that are refueled on a regular basis. It will NOT sit for extended periods of time and not go bad. Seafoam will help your generator after you get it running. You will need to use choke spray cleaner to blow out and thoroughly clean the carb. Otherwise, replace the fuel completely and then the carb!

my 2 cents.....

 

[TerribleTim68]

Yeah, the struggle there is getting non-ethanol fuel. We certainly don't have an abundance of sources, and the one place that we did have is currently under construction and they made it where you can't tow a trailer in to the pump.

 

[TerribleTim68]

Okay guys, new problem.

I put a new carb on it and it fired up. Ran it for about 10 minutes, no problems at all. Shut it down and now it won't fire back up. It will light off, but as soon as you turn loose of the start button it dies.
Edit - Okay, I let it sit for 10-15 minutes and it fired back up. Is it possible this thing is flooding itself out when it shuts down?

Thoughts?

 

[jeffdee]

Yeah, the struggle there is getting non-ethanol fuel. We certainly don't have an abundance of sources, and the one place that we did have is currently under construction and they made it where you can't tow a trailer in to the pump.

i use 5 gallon containers to transport the non ethanol fuel to put in the fuel cell. Here in the southeast we have many of the Murphy USA’s with non ethanol regular grade gasoline.
Good luck!

 

[WillyBill]

i use 5 gallon containers to transport the non ethanol fuel to put in the fuel cell. Here in the southeast we have many of the Murphy USA’s with non ethanol regular grade gasoline.
Good luck!

Download free app - PureGas.Org - It will tell you closest choices for ethanol free gas. Works great on the road. As more people have a need for Ethanol Free more stations are carrying and advertising it. Been using the app for a couple of years now.

WB

 

[jleavitt11]

I have been running regular gas in our Onan for years and never had a problem. I sits for 5 months during the winter and the generator fires right up. I don't think non ethanol is the issue.