onan generator help.. please!!!

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Sounds like you want to fix it yourself to me. Most of the onan carbs get fouled if they set too long. Some will say  to replace it, You can remove and tear it down to clean it. Be very careful taking it apart and keep everything in order. There is very small jets and passages in the carb, they all have to be clean to work right. Before you take the carb apart, run a jumper wire to run the fuel pump and see if it'll run. If it will run at all you can get some seafoam and mix it in the fuel, let it run with that and see what it does.
 
I was wondering if the carb could be plugged and it's just not getting fuel.. the problem with that is when I added gas to the spark plugs wouldn't it have fired and possibly ran for a second. I'm guessing if it has decent compression than it must be the valves. If the compression is shot I'm curious how to fix it and I may have to go to a different site to do it.
 
Your model number doesn't jibe. Perhaps it is 5bgfma26105f not 5bcfma26105f.

Here's a link to Onan's online pdf manual

http://www.cumminsonan.com/www/pdf/manuals_service/0914-0507.pdf

If you have sticky valves you'll have low compression. Fire out the intake or exhaust would indicate which valve(s) are sticking. If sticking from exposure to weather, such as rain into the carb forget that engine. If sticking from gummy oil there are tricks.

Low compression would allow the starter to spin that engine at high speed or if one cylinder was good and the other low the starter would lope around the hard then easy load. Fire is a sign that at least there is spark.

Heres a link I have found helpful.

http://www.smokstak.com/forum/forumdisplay.php?f=1

Bill
 
Ok. Here are a couple questions. 1st being should I take the generator off the engine or do you think I may be able to do this without doing that. 2nd this marquis 5000 is a tough generator to find. The marquis gold 5500 is much easier to find and I'm wondering if outlet ac power would be the same pin connectors. Just wondering if the engine is bad it appears to be tough to find a replacement engine.
 
There is a lot of good suggestions here but you first must determine if you have compression. If you have compression then determine whether you are getting fuel. You cannot get fuel into the combustion chamber unless you have compression. Lack of compression on an Onan is generally stuck valves from sitting. It is doable by yourself if you are handy with tools. I have rebuilt several of the old cast iron Onans which were really bad about sticky valves if you did not run them frequently. Dirty carburetors are very common also when the generator is not run. Also as long as this generator has set it would not surprise me if you do not have both problems.
 
Regarding the pin-outs on the connectors.. Very likely they will be the same but alas that is not 100%.  Downloading of the owner's manual will tell you for sure since if they are then the same remote switch works with both.
 
OK redneck compression guage......remove the spark plugs and hold your thumb over the hole, turn the engine over with the starter and if it blows your thumb off the hole on the compression stroke and tries to suck your thumb a little when it is on the intake stroke...thennnnnn you have some compression. Like we said before I bet it is stuck valves.

If you really want to try to fix it then remove the cylinder head (thats what the spark plugs screw into) You willhave to take the exhaust and cowling off to get to the 1/2 in bolts holding the head on.  When you get that far, spin the engine with the starter and see if all the valves go back and forth....all the way closed and all the way open. DONT beat on the top of the valve..not yet...get that far first OK.
 
ok... i'll be working 12 hour shifts for the next few days so when I get a chance i'll check it all out.. it might be a couple days before I report back.. thank you all so far and don't give up on me..
 
it helps if you understand the principle of operation....MT4runner was right on (It's an internal combustion engine.
Suck-squeeze-bang-blow...but first it has to turn before it can fire!)

Its a 4 stroke or 4 cycle engine...The piston goes, down, up, and down again.and up again or in your case it goes sideways. that is a complete combustion cycle......1st down ...intake valve opens and it sucks fuel and air in. 1st up all valves closed and it squeezes the mixture together. at that point the spark plug fires almost before it get to the top. the fuel explodes and blows the piston down on its second trip...momentum pushes the piston up on its second trip up and the exhaust valves open allowing the burnt gases to be blown out.......suck squeeze bang blow....easy isnt it....

Sorry if this seems so simplistic but I just wanted to explain the basic and not knowing how much you already know this is a good place to start

If I got any part of this wrong I hope someone comes in to help...later Will
 
Thanks.. yeah I understand how it works, I've just never really taken one apart other than carb cleaning. If the valves are stuck let's say in the up position what do I do. Try spraying the Crap out of it with some wd40 or something like that or do I have to take the generator off the motor,and pull it all apart to get to the,back sides of the valves somehow. I may have enough time to take the cover off tomorrow and look to see what's up. I'll take a pic, maybe a YouTube video and post it here so you all can see exactly.


From everything I've read and researched on the net I'm going to have to agree with you that the valve is stuck open from just being old and not run enough. I'll find out tomorrow what it is. My next question is the fuel pump. Now I haven't jumpered it yet but if I do and the pump works my troubleshooting thoughts are that it is either a bad control board which I think is unlikely or a lose wire or chewed wire. What else could it be? Or I could possibly not be thinking it through. The fuel delivery seems pretty simple to me, but I'm sure I'm missing something. The fuel filter has recently been replaced, but I'm positive the fuel pump isn't working when I push the start button and from a few of the schematics I've seen it should be sending 12 volts to the fuel pump when I push the start button. Fuel pump may be bad but if it's not where do I go from there?
 
Did you look at my last post?

What model do you have?

A lot of people are guessing you have the two cylinder flathead boxer. The model number in your second post doesn't work, nothing comes up.

5bcfma... maybe should be 5bgfma...
The 5bgfma.... is an overhead valve engine. It comes up as a portable setup.
So until we know what you really have everybody is stabbing in the dark.

Bill
 
driftless shifter said:
Did you look at my last post?

What model do you have?

A lot of people are guessing you have the two cylinder flathead boxer. The model number in your second post doesn't work, nothing comes up.

5bcfma... maybe should be 5bgfma...
The 5bgfma.... is an overhead valve engine. It comes up as a portable setup.
So until we know what you really have everybody is stabbing in the dark.

Bill
Click to expand...

Good point...I am one of those guessing it is a horizontal 2 cylinder also...my bad
 
I'm sorry.. yes it is a horizontal 2 cylinder.Model#5BGMFA26105F
SERIAL# B95333643... what site are you looking it up on. I went to Cummins,onan and I can't find. Anything on it. Sorry about that. The c is a g. I should have a n answered that question earlier.

Also i m glad this reminded me. This This is an onan marquis 5000. I am looking everywhere online to order new head gaskets for it and I can't seem to locate them. I'm sure the gaskets will be shot when I pull the head off so I'm going to need to buy new head gaskets. If anyone can post what I'm going to need and where I can get it I would appreciate it. Thanks so much.
 
At this point IMHO you should gather all the parts up and take it to an Onan repair shop. I believe some camping worlds are both Onan dealers and repair stations. But you can easily find one close to you online.

You said you were an industrial electrician. Look at it this way... What you have is similar to an AC unit with a locked rotor.

Just like the AC motor, your geny needs a lot of amps to start the engine and get the windings up to full output. Look up your geny's user guide online to see how many cranking amps it requires to kick over. My Onan 5500 needs a min of 650, so I gave it a 900 cold cranking amp battery. And if you didn't know, there is a big difference between a cranking or starter battery, and a deep cycle used to power RV lighting and electric trolling motors.

With all due respect...  I say call it a day and bring in the pros from dover. You have made a valiant effort, but it's like the man said... Know when to hold um, know when to fold um. And yes, I say that from experience.

Jeff
 
I do not know how many cranking amps my Onan 5500 takes but when I accidently ran all the batteries down on this RV, both House and Main, to the point where the steps would not extend I grabbed the garden tractor batteries off my wife's scooter and fired it right up.... Waited a while for the 80 camp converter to do some converting.. and fired up the main engine.

Though I agree with the person who said that there is a big difference between starting batteries and deep cycle which is what we should be using for house (And the genny normally starts on the house bank though there are exceptions).

When it comes to starting, I have less than 75 amp hours of chassis battery and over 500 of House (230 are the original bank, I more than doubled it).

So, say a 150 amp starter current (Kind of high) is 2x the starting battery's c/20 rating, and just over 1/4 of the house. Not a big load at all.
 
This might be the one. BGM is your model, F is your spec. The F spec is important, don't adjust anything to the wrong spec. The manual covers propane fueled gensets model NHM as well. you should show 75 psi for compression. 10% low, high 60's, is probably OK.

Bill

Forgot the link, DOH!

http://www.cumminsonan.com/www/pdf/manuals/965-0531B.pdf
 
Thanks for your thoughts and concerns. Bottom line is I'm going to rebuild this thing if I have to. I'm that dedicated,to,this project. My mother had it taken to a place in canton south that charged her 900 bucks to basically look at it and scratch their heads. I refuse let that happen to her again. If the engine is beyond repair I'll figure something out. 5k for a new one is unacceptable to me when I'm capable of trying.
 
The 4000W Onans go for $500-600 on eBay. :)

Would 4kW handle her needs, or will she plan to run two AC's?
 
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