Onan microlite 2800 generator issues

[concretebox]

I'm prepping for solar, but since my ClassB came with a Genny I'm planning on keeping it for backup. It wasn't starting so I replaced the sparkplug (which was fouled) the air filter (which was filthy) and cleaned out the carb bowl (just the bowl). The exhaust was also lose so I fixed that. It ran fine on the ground, but when I reinstalled it in the RV, it wouldn't start.

I took it back down and has was spitting out the exhaust and the spark plug was black and wet with fuel. I cleaned the plug with WD40 and sandpaper. I left the spark plug out and let the fuel evaporate overnight. Today it stated and ran for a few minutes, then quit.

The sparkplug was black and wet again. I cleaned it and put it back in and it ran for a few seconds. I tried adjusting the carb main screw, no effect. Each time it ran less, now it won't start.

I'm thinking I need to disassemble the carb and give it a through cleaning and replace the sparkplug again.

From what I've read On an doesn't sell carburetor parts, just a replacement carb assembly ($200 on eBay). Can I use"universal" carb replacement parts? Any "hillbilly" engineering solutions?

 

[DC Fuse]

concretebox wrote: I'm thinking I need to disassemble the carb and give it a through cleaning and replace the sparkplug again.

Yes, you are on the right track. What is happening is your vacuum or mechanical fuel pump wants to do its job pumping gas but the carb is not doing its job by regulating the amount.
You either have a pinhole in your carbs float allowing it to fill w/fuel and not float or, most likely, the "needle" that's opened by the float is stuck open from tarnish thus allowing excess fuel into motor causing it to stall.
In the old days this would cause fuel to leave carb thru a stem on top of carb showing operator of the problem.
Nowadays it just dumps excess fuel into motor stalling it.

 

[Vonbrown]

I agree, the float sounds like the problem. Check to make sure the needle valve is properly seated. (it's on the pivot end of the float) There is a steel pin securing the float that can be easily removed and from there you can tell if the float is filled with fuel by holding it in your hand. (be careful not to lose the needle valve) Upon reassembly, gently hold the bowl assemble at eye level and hold the float up (thereby closing the needle valve to it's seat and the float should almost be level. (there is a precise measurement from the bottom of the carb assembly and the top of the float, but without documentation and the remote location from you, this is the best I can do) Good Luck Concretebox!

 

[Donedirtcheap]

Is the choke stuck or out of adjustment?

 

[Vonbrown]

Another good answer!, sheeze, I should keep my mouth shut. Doing diagnoses over the internet is not my style. With the choke not opening enough after it starts would make the engine stall because of too much fuel and that would blacken the plugs. I would be more helpful if I was there. (see you at the RTR!)

 

[highdesertranger]

well everybody is on the right track here, it's flooding out. if you a comfortable with tearing into the carb I say go for it just be extra careful with the gaskets if they are not available. that's seem like to much for a carb shop around. o yeah like ddc said check the choke first. highdesertranger

 

[concretebox]

Progress report:

I removed, disassembled, cleaned and reinstalled the carb. It was actually pretty easy. I was able to reuse the gaskets. I used some gasket sealer just in case. There was a gasket like thing between the carb and the air filter. It was like foam. The carb cleaner dissolved it. I replaced it with foam weather striping. It seems to work well.

I must have caused a short somehow and the fuel pump stopped working. It took me a while to figure out it was just a fuse. I then adjusted the main and idle screws on the carb to factory. I also replaced the spark plug and fixed a loose wire on the ignition coil. I also adjusted the choke as the book (and you folks) suggested. It started! I was happy...for a moment.

It now starts but quits after 2-3 minutes. It has fuel. I'm assuming it has good spark if it runs that long. Spark is dry and brown.

From what I've read in the manual it's time to consider the governor as a culprit. It "hunts." The governor arm is constantly moving. The book says to hook a voltmeter and frequency meter to the AC output and adjust the governor screws and carb screws in a particular sequence to get specific frequencies and voltages under load and no load.

Assuming I can find a frequency meter, how do I hook up two instruments to the AC output and a load (I was thinking a battery charger on a low/dead battery would be a good test load)?

 

[Donedirtcheap]

I wouldn't blame the gov yet. Dont mess with it yet as some engines will suffer internal gear damage if adjusted improperly. If its hunting, it sounds more like a lean condition. You probably fixed the rich issue but now it may be lean on the main jet or not be getting enough fuel to the bowl. Dieing out and hunting are often lean conditions. First, richen the main. If that doesn't help Start it and as it dies out either close the choke a little or give it a slight sniff of starting fluid to falsely richen it. If it recovers for a second you know you have a lean condition. Lean= adjustments closed too much, jets plugged, wrong float adjustment, carb to eng side air leak (manifold), suction side of pump fuel line air leak, weak pump.

 

[Donedirtcheap]

2 or 3 minutes is probably about enough time to empty the bowl.

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2 or 3 minutes is probably about enough time to empty the bowl if it has low pump output or some form of restriction. Pinched lines? I have seen weird fuel filter issues that dont flow correctly at times. One way to fake it out and eliminate the supply side is to connect a small tank or bottle directly to the carb. Process of elimination, one step at a time so as to not create problems on top of current problem. Sorry if I worded anything wrong and hurt anyone's feelings. If the generator thinks I being to judgmental, slap it for me.

 

[concretebox]

Well, I really F'ed this up. I busted the part of the carb that holds the float pin. Any glue will be dissolved by the gas. So I could try welding, but it so small I think my chances are of doing that well are pretty slim.

So unless you all have another suggestion, this carb is garbage now.

 

[highdesertranger]

whoa hold on there. jb-weld is gas proof just let it cure before exposing to gas. I know have used it several times to repair carbs even fuel tanks, even plastic fuel tanks. highdesertranger

 

[anm]

I wouldn't blame the gov yet. Dont mess with it yet as some engines will suffer internal gear damage if adjusted improperly. If its hunting, it sounds more like a lean condition. You probably fixed the rich issue but now it may be lean on the main jet or not be getting enough fuel to the bowl. Dieing out and hunting are often lean conditions. First, richen the main. If that doesn't help Start it and as it dies out either close the choke a little or give it a slight sniff of starting fluid to falsely richen it. If it recovers for a second you know you have a lean condition. Lean= adjustments closed too much, jets plugged, wrong float adjustment, carb to eng side air leak (manifold), suction side of pump fuel line air leak, weak pump.

... clogged fuel filter, clogged fuel line, has it been sitting for a long while? gasoline evaporates and leaves a varnish-like residue behind which can easily clog a filter, use an air-compressor and blow out the fuel line back to the tank...

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Well, I really F'ed this up. I busted the part of the carb that holds the float pin. Any glue will be dissolved by the gas. So I could try welding, but it so small I think my chances are of doing that well are pretty slim.

So unless you all have another suggestion, this carb is garbage now.

Are there two places like that? where the pin goes into a hole? if so you could put it together and try it. Buoyancy is going to push the float up, and the pin up into the 'half-hole' it fits into... worth a try...

 

[Donedirtcheap]

I have used SEALALL to reseal expansion plugs in small engine carbs. I have never tried it but JB Weld may also work.

http://www.eclecticproducts.com/sealall.htm

 

[concretebox]

I fixed the carb with JB weld. I put it back together and started working on it. It starts and runs for a few minutes then quits. I tried everything reasonable. I read the service manual's instructions for adjusting the carb and governor several times. I plugged an electric heater into it through a Kill-a-Watt to measure the frequency and volts. I just couldn't get it to work. I'm giving up now. Maybe someone will want to buy it from me. What do you think I should ask for it? New they are $2500.

 

[SoulRaven]

Concretebox, My onan 2800 quit working after I had my vans fuel line repaired. The mechanics who did the fuel line tried to get it going and screwed it up even more. Then they wanted to take it out and work on it. I told them to just leave it be and took it to Cummins Southern Plains in Ft. Worth. Cost $130.00 for them to find the problem. I don't know if it's worth that to you but to me it was money well spent. Might be worth knowing what's wrong before trying to sell it. JMHO.

 

[MikeRuth]

Yeah don't give up just yet,. It starts runs for a few then quits, OK. So how long before you can start it again and it quits?
I can't quite tell if this has a electric fuel pump or just a vacuum draw by the engine. Is the plug dry when it quits?
If so fuel starvation. filter replaced? Kinked lines, etc.

If you don't have it, here is a link to the manual..http://www.cumminsonan.com/www/pdf/manuals/981-0506.pdf

As a former small engine repair guy, I'd have to say the carb rebuild was less than proper. Not bagging on you, kudos for the effort.
It should have been disassembled. Soaked in Carb cleaner, rinsed and dried, all new gaskets and needle and seat. Float set and adjusting needles set to factory starting positions.

I can't tell you how many times I saw folks do a "carb" job that didn't work, after a proper rebuild, all was well.

Mike R

 

[akrvbob]

I know you don't want to hear this, but the Onans aren't good generators. Go to any RV forum and do a search on "Problems with Onan Generator" and you will get page and pages of hits.

The way to solve the problem forever is to replace it with a Honda or Yamaha. They both sell electric start models. Your best choice is the Honda 3000. It's a lot of money but it will run for decades trouble-free!
Bob

 

[concretebox]

OK. Call me the boy who cried wolf. I was ready to quit, but after reading your comments I took the fuel filter out and ran it without. Surprise it works! So I bought a replacement fuel filter and installed it. After a little adjustment to the screws is running well now.

One last thing, I noticed some oil leaking from the head cover. I removed the head cover, cleaned up the mounting surface and applied some liquid gasket. In 24 hours I'll know if the liquid gasket works.

 

[highdesertranger]

glad you got it going. I did a quick read on that manual mike ruth posted and had a few suggestions one of which was the filter. first rule of trouble shooting a system is to replace the consumables ie filters, plugs, etc. I told you the jb weld would work I have used it many times on fuel systems, for emergencies or to repair parts that were not available. this is just an observation but I believe most of the problems with rvs and onan generators is the long period of time they sit between trips, with todays fuel this reeks havoc with fuel systems. highdesertranger

 

[LeeRevell]

Glad you got it working! Something so simple so often brings us to a halt.