Oanan generator problem

jimgram · 05-23-2017, 07:13 AM

I'm looking for some advise regarding my Onan 5.5 KW gasoline generator (factory installed). It set in Camping World (while the trailer was undergoing some repairs) for about 90 days without being run. When I tried to start it it would fire off but immediately quit. I assumed gummed up carb (although I had added stabilizer when it was first fueled). I checked the fuel pump and even though it was supplying fuel to the carb. it shows signs of overheating (some rubbery substance is was oozing out of two small holes in the body of the pump, so I purchased and installed a new pump. The filter showed easy flow through. I drained the carb float bowl and again ran the pump. Full flow of fuel into and out of the carb. The engine always starts (after priming for about 60 seconds) and runs for 5 to 60 seconds then quits. While it's running it generally is running poorly, speeding up then slowing down. I've put a voltmeter on the wire to the pump and the voltage is stable until the engine quits - then it goes off, as I would expect. The error code is always 36 - no fuel. But I've always checked the carb bowl and it's full. I've sprayed carb cleaner in to the throttle and also filled the float bowl with carb cleaner.

Short of removing and dismantling the carburetor, can anyone think of any other causes? I did once get the engine to run for as long as maybe 5 minutes by holding the choke at about half. There is a rotary switch or potentiometer or actuator (I can't tell which) but it's attached to the choke and throttle levers with some complicated rotary spring linkages and I think that makes it suspect.

I'm leaving on a long (2500) mile trip this Sunday (5/28) sans generator - so I'm can't take it anywhere for service, therefore hoping for a miracle. I'll only use the generator to pre-cool the cabin during the last 30-45 minute of each leg of our trip.

Sundancer330 · 05-23-2017, 07:36 AM

It sounds like a gummed up carb when you have to choke it to somewhat run. I have become a big believer in Seafoam carb cleaner, I have a 6500w Honda generator that was doing the same thing as yours. Since your gen probably pulls it fuel from the main gas tank it will take a bit more work, you could just pour some in the gas tank and run the gen best you can to get the treated gas in the carb. What I did was fill a cup half full of Seafoam and removed the gas line going to the carb and started the gen sucking the Seafoam in for several seconds then let it sit overnight and repeat the next day, by day three it started and runs like new, no hunting up and down with RPMs, didn't need the choke to run. You have to get the inside jets and passages clean, spraying the intake will just make it look pretty but won't clean inside where the problem is.

imjustdave · 05-23-2017, 07:46 AM

Ethonal free gas is your friend, so is draining the carb after use. If it was me I would order a new carb as a backup, then I would dismantle the one you have and once you see all the crud in there will understand. Ethonal causes lots of issues like your seeing.

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Mopar_Earl · 05-23-2017, 07:48 AM

Seafoam does wonders. You should always treat your gasoline. Like the poster said above, run the genset on pure seafoam. If it doesn't clean up, buy a new carb. I don't believe they make kits anymore. If you don't know how to take it apart and salvage the gaskets/seals it's best to buy a new carb. Or let someone that knows how to clean the carb do it.

When storing, I'd install a manual valve in the fuel line so you can close it and run the engine out of fuel. Than drain the carb bowl if it has a drain.

Always, I mean always treat the gasoline every time you get gasoline.

Earl

Sundancer330 · 05-23-2017, 07:56 AM

Here is a good video on cleaning the Onan carb, or you can get a replacement on Amazon for about $270.

https://youtu.be/CLLI359w2RM

imjustdave · 05-23-2017, 08:21 AM

I should mention using ethonal gas isn't the issue... its when it sits in the carb absorbing water then eventually evaporating a little then leaving varnish like gunk and corrosion from the water in the worst place for contaminants.

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Sundancer330 · 05-23-2017, 09:42 AM

Quote:

Originally Posted by imjustdave

I should mention using ethonal gas isn't the issue... its when it sits in the carb absorbing water then eventually evaporating a little then leaving varnish like gunk and corrosion from the water in the worst place for contaminants.

Yes water is an issue but ethanol absorbs more water causing bigger problems. I buy 92 octane ethanol free gas now to use in my lawn tractor and 9.9 outboard motor after having the carbs gummed up with crud from ethanol gas. Most marinas use ethanol free gas with additives to remove moisture. Here is part of an article about ethanol gas, its a much bigger issue in engines that are not run daily like our cars and trucks.

Ethanol causes damage to fuel systems and engines that pure gasoline does not. The most critical problems are water contamination and fuel separation. Ethanol attracts and absorbs water, including water from the air. When the gasohol absorbs enough water, fuel water contamination occurs in the car’s gas tank and that affects engine performance. If the car sits for a while, fuel separation occurs; this is where the gas and water form layers in the gas tank and if the motor sucks up the water layer into the engine, serious costly, damage happens.

PonyExpress · 05-23-2017, 10:19 AM

I would drain all old fuel from genset and start with fresh and sede how that does and use seafoam or BG

Mopar_Earl · 05-23-2017, 10:51 AM

This is why I prefer diesel, LP or natural gas. We plan to install an Onan 5500 in our 2017 293RKDS and we'll definitely be using the LP model.

Earl

jimgram · 05-23-2017, 02:25 PM

Thanks for all of the advise - After watching a few of the YouTubes you directed me to I'm sure it is a gummed up carb. A pro said don't even think about repairing the carb - could create a fire hazard. I'm trying to order a new one but delivery will be a problem. I would have much rather had a diesel but I don't think that was an option. Also, how much heavier would a diesel be? I have LP anyway so that would have been a good choice. Is there any such thing as a gasoline to LP conversion?

TexasRT · 05-23-2017, 03:17 PM

After having the "gumming" issue on my first onan genset, and after replacing the carb I installed a fuel shutoff valve in the fuel line. Turn on to run, turn it off and let the carb run dry to shut down. I've never had another problem on either genset I've owned after doing that. Good luck

Jagiven · 05-23-2017, 04:27 PM

Ethonal sucks! The main downfall of a built in generator is having to use the coaches fuel tank, and all the Ethonal.

You can buy Ethonal free gas, at first it takes a bit of effort to find it, or know what to look for.

I run Ethonal free in all my small motors and old cars. Tuneups are a thing of the past since switching.

bdreinv · 05-23-2017, 04:46 PM

Had 5500 in 06 Toy Hauler only thing ever went wrong replaced fuel pump.Use carb cleaner by Cummins and adjusted valves at about 600 hours. Always use fuel stabilizer. Happy Trails

bdreinv · 05-23-2017, 04:47 PM

PS check the linkage on your choke tends to get gummed up. Hope that helps.

imjustdave · 05-23-2017, 07:11 PM

Usage is key for sure. Yes you could run lp in gasoline engine lots of people do it but no idea how hard it would be to convert down side is you burn a lot more propane as it has less btu in the fuel. Diesel would be awesome. Been dreaming of that for awhile.

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Mopar_Earl · 05-23-2017, 08:00 PM

The burn a lot more lp isnt true. Slightly more. Not a lot more, slightly. It just seems to burn more because the lp tanks don't have many gallons in them. Look at the Onan specs on fuel consumption for the same unit on lp vs gasoline.

Earl

edatlanta · 05-24-2017, 03:46 AM

Quote:

Originally Posted by Mopar_Earl

This is why I prefer diesel, LP or natural gas. We plan to install an Onan 5500 in our 2017 293RKDS and we'll definitely be using the LP model.

Earl

I full time and have approx 435 hours on my Onan 5500 EVAP and it has never once failed me. I use non-ethanol gas 99% of the time (unless I just can't get it) and always keep Sta-Bil Marine Formula in the gas. If I do have to use some ethanol gas I make sure I run the tank dry before refilling with my usual non-ethanol/Sta-Bil mix. I also run the generator 1 hour under a partial load the first of every month. I NEVER fail to do this.

After 7 years full time use - zero Onan problems.

Mopar_Earl · 05-24-2017, 05:46 AM

Quote:

Originally Posted by edatlanta

I full time and have approx 435 hours on my Onan 5500 EVAP and it has never once failed me. I use non-ethanol gas 99% of the time (unless I just can't get it) and always keep Sta-Bil Marine Formula in the gas. If I do have to use some ethanol gas I make sure I run the tank dry before refilling with my usual non-ethanol/Sta-Bil mix. I also run the generator 1 hour under a partial load the first of every month. I NEVER fail to do this.

After 7 years full time use - zero Onan problems.

That's why. But most people don't take care of their equipment like that. That's why I said, always always always use fuel treatment. Run the engine out of fuel and drain the carb bowl when not in use. Should never gum a carb up that way.
LP is just a more simple, less maintenance way to go. No messing with fuel treatment. No messing with draining the carb bowl. Burns cleaner and less toxic exhaust. No messing with fuel cans and spills. All kinds of pros to using LP. All kinds of cons for gasoline.
If you must use a gasoline genset, I highly recommend one with fuel injection. Onan offers a 5500 with fuel injection.

Earl

Fiddich · 05-24-2017, 06:02 AM

A pro said not to rebuild the carb? Did the pro offer to rebuild it for you? If he didn't, he is no pro. If you don't feel comfortable rebuilding, don't. But a fire hazard? Watch a youtube video or two. Rebuilding carbs is very easy. Get the right kit, remove all the rubber bits, spray it liberally with carb cleaner, replace the rubber bits and go. This is simplified but not by much. Seriously, watch a few videos and see if you are comfortable. THe worst thing that will happen is you will get it out of adjustment. So you should adjust it.

Victoria · 05-24-2017, 07:02 AM

Quote:

Originally Posted by Fiddich

A pro said not to rebuild the carb? Did the pro offer to rebuild it for you? If he didn't, he is no pro. If you don't feel comfortable rebuilding, don't. But a fire hazard? Watch a youtube video or two. Rebuilding carbs is very easy. Get the right kit, remove all the rubber bits, spray it liberally with carb cleaner, replace the rubber bits and go. This is simplified but not by much. Seriously, watch a few videos and see if you are comfortable. THe worst thing tuhat will happen is you will get it out of adjustment. So you should adjust it.

or you could catch it on fire, which husband we did, twice. lol. we all know you are not supposed to use carb cleaner while turning it over but most DIYers do...so I am gonna ride the coat tails here if you don't mind. we had this exact problem on a new to us Octane Oanan generator. Husband replaced the carb and discovered that the things he had done trying to clean then old carb had fried a fuse at the battery. (He used the charger to the selenoid to get it to turn over) Then the fuel pump rocker switch and inside camper start button have no power. searched for blown fuses, found one at the battery, Replaced the fuse, left the camper for two hours and came home to hearing the generator trying to turn over on its own. Husband had to disconnect a cable to make it stop. we think a new selenoid is in order but what about the starter switch issue?

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