Onan 4000 generator help

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ctrain22

Member
Joined
Nov 16, 2023
Posts
7
Location
Ventura,CA
I have a 2000 Minnie Class C with an Onan 4000 Generator.

I just bought it. It had been sitting for a couple of years and the mice had a great time chewing some wires.

The generator cranks but won't start. It's getting fuel and has spark. Air intake is clear. While poking around, I found a broken wire that connects to the fuel cut off solenoid. It goes to a block of wires behind the carb. It looks like they got to a couple wires. What's left of the piece that goes to the fuel cut off is on the lower left of the picture My question is, which wire from the block would it connect to? And where would the other wires connect to? Thanks.PXL_20231116_164824596.jpg
PXL_20231116_170653749.jpg
 
First,

If you have gas and spark then one probable issue is that the carb is probably gummed up from deposits from the fuel drying up and blocking the carb.

Did you disconnect the fuel line and press the start switch down to prime to verify fuel delivery?

If you did that than the above is probable.

That is common in generators that sit for even less time.

That has happened to me twice from not starting the generator enough.

The first time last year a mobile tech was able to get mine going with spray carb cleaner.

This time after trying that several times it did not work.

I am having my carb rebuilt next Monday.

They are replacing mine with a rebuild of a factory Onan carb and then taking mine to rebuild.

They cautioned me to only use an actual Onan carb. There are cheaper ones online but are not as reliable.

They are charging me $189.00 for the rebuilt carb and the listed price for a new factory Onan carb is much higher than that.

Someone else may be able to help you with the wiring.

Good Luck.
 
Last edited:
First off, I would note that is not the original generator for your RV, looking at the data plate it is an Onan KY4000 Spec R, which makes it several years newer than your coach.

Here is the Spec P installation manual, which has some wiring diagrams in it, you need wiring diagram 0611-1267 if I am reading the photo of your data plate correctly (might be 87) to see exact wiring on your Spec R

 
They cautioned me to only use an actual Onan carb. There are cheaper ones online but are not as reliable.
I disagree with that. A pin broke on my Y2k Onan OEM carb. The cheap $40.00 carb on Amazon uses a thicker shaft at the same area. And it has not given me any issues. I gave it a 5-star review on Amazon.

-Don- Mission, TX
 
My question is, which wire from the block would it connect to? And where would the other wires connect to?
Here is a link to download a copy of the installation instructions for the generator that you have, spec R. Appendix A, on page 57 is the wiring diagram for your set. You will probably need to get your meter out and trace the cut wires to see where they go.
 
You may be right about the carb, but I have heard from two different sources that the cheap Chinese carbs can be a problem.

Glad that you did not have any problem with it.

I actually have one of those in my spare parts box that I bought when I was buying carb maintenance parts last year from amazon.

With the labor cost, I took the service managers suggestion and went with the rebuild of the original Onan one that they are installing Monday.

If my hands were more steady I would just go ahead and try the cheap one.

It is in my give away box for Quartzsite, if anyone wants it.
 
My take on it is that the cheap Chinese carburetors are a luck of the draw, some are built better than others, some are jetted way out of factory spec, and there is no consistency from one to the next (some have soft point needles, some have hard point, etc.) , it seems they are built with whatever parts may be on hand. Lots of people on the RV forums have reported problems with them, a few people are happy with them.
 
mice and rats love that spot on those onans. wood rats got to my 2001 microquiet. they nested up in there and had some babies. it happened within a couple of months. i went to start the generator and it would only crank. would not start. once i opened the front cover i saw the nest, removed it along with the babies and peeked in at that connector. they chewed several wires. i believe one was the fuel cutoff but they got to a couple more. i had to remove the generator to get at the connector. i was able to solder the wires back together and it was good to go.

after that fiasco, i fabricated two screens to keep the rats and mice out. i put one at the cooling air intake vent on the front cover and custom made one that fits around the exhaust pipe where the cooling air exits.

i highly recommend to get those two points of air flow screened up. they will however restrict the air flow some. i remove mine in high heat but in moderate to low heat, i leave them in place..
 
Does anyone have, or can get a picture of the plug with all the wires connected? If I could see where each wire is supposed to go I think I can fix it. The wiring diagrams are a little to hard for me to read. A better visual of the connector would be much better.
 
Does anyone have, or can get a picture of the plug with all the wires connected?
Where is that connector? It looks like it is behind the genny fan in this photo, but I do not recall a connector being there:

84143-0ad835ee7141231ade1038d9d7c7dd2d.jpg

Anyway, I tried to take a photo of what I think is that area on my Y2k RV, but I could not get a camera in there without the genny being removed.

-Don- Auburn, CA
 
1-800-cummins. have your model and serial # handy. they will usually send related documents to an email address.

check to see how close you are to a cummins service center. i have never used a franchised dealer and would not recommend a franchised dealer for this problem. go direct to cummins.
 
Where is that connector? It looks like it is behind the genny fan in this photo, but I do not recall a connector being there:

84143-0ad835ee7141231ade1038d9d7c7dd2d.jpg

Anyway, I tried to take a photo of what I think is that area on my Y2k RV, but I could not get a camera in there without the genny being removed.

-Don- Auburn, CA
behind the carb.
 

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