Onan 4000

[bigguyone]

Hello,  I need help please,    I have a Onan 4.0  KY-FA/26100H  wouldn't stay running, found carb was bad so replaced along with fuel pump.  It ran great, used it often.  Then one day it stopped charging, I did all the checks and was told reg may have went bad so got a new one. That didn't fix the prob. after a few months of messing with it I got with Flights system, they said sounds like a bad reg so sent it with control board to have check.  They said both check out good, so back into it we go and cleaned slip rings, got 26 ohms, replaced brush holder (it broke taking it off) I check stator & it was ok.  So I got with Flight system again & went over it again, that when I was told the stator was bad, said one reading should be 5 ohms not .5 ohms.  So I get a new Stator & Rotor, put it all back together, start it up on bench, its charging so get it back in RV. I start it up and it dont sound like it running a little sluggish, I thought something get in carb so I clean it out but didn't help, I know they have really small passages and maybe it got stopped up from setting. I buy a new carb but that dint fix it.  But this is  what I got, it runs, charges 117 to 119 just with refirg on about the same, & with the convertor it drops to 114/115, turn a/c on it drops but will stay at about 112 but eng is having a hard time, after about 10 min it drops down to 108 or lower and then want to stall before I can turn it off. I have even tried to see if I could open the carb a little more thinking I mite have knock the gov out a little but its wide open & this is with ether carb on it, so it just seems like its not getting full throttle even though its open all the way. 

So anything anybody mite know what to do?
Thanks Dave

 

[Isaac-1]

It sounds like an engine side issue, have you checked the valve lash?

 

[bigguyone]

Hi  no but it seem to run fine be for,  & before the charging went out it didn't have any prob. but now after putting new rotor and stator in its like its laboring to keep up.  That's why I thought the carb messed up & I put a new one on.  Its like it cant get enuf speed when under a load & the throttle is wide open. 

 

[Isaac-1]

Valve lash being out of spec can cause this symptom as the engine warms up

 

[ChasA]

How many hours does the genny have on it?

 

[bigguyone]

Never touch the eng just gen side, everything was fine till it stop making 110 volts. I replaced everything, rotor, stator, bush holder, regulator. Now it makes 110 volts but struggles doing it.  Its like timing  is off, but I know the pin and key was lined up when it all was put back together. It there a way  to check timing with out taking it out of RV and opening it up?

 

[bigguyone]

Oh forgot. To say it has 700 hours. On it  it's in a 99 RV

 

[Isaac-1]

Even if it is not the valve lash, if it has not been checked and adjusted before, you are past due, I think Onan calls for adjusting every 500 hours.

 

[bigguyone]

Ok didn't know that but will check I have maybe put 50 or so hours on it myself.  Like I said its like timing is off a little.  This thing is eating my lunch. LOL......

 

[Henry J Fate]

Unless the adjustment nuts have loosened, it would be unlikely that valves would cause engine failure especially at 700 hours.

Probably a fuel/gas issue. It sounds like it could possibly be a governor issue. Take a close look at the assembly both at the carb and in the actuator area at the other side of the linkage. You can manually operate the throttle while it is running. Be sure the choke is off after starting and that it stays off. Clean air cleaner and a properly gapped plug.

Thoroughly cleaning the carb requires removal. Since you just replaced it with a new one, any new blockages would have to come from the gas flow to it. Determine whether or not you have a fuel contamination issue.

You could also think about an axillary fuel source so that you can be sure the fuel source is good. Any rubber fuel line at 21 years should be considered a problem especially at connection points where it is usually a good idea to cut the bad ends back or replace the entire line.

 

[bigguyone]

Basically I have done just about all that new lines, throttle is wide open, fresh gas.  So don't know what else it could be,  going to take it out and start looking to see if I can see anything.....

 

[X-Roughneck]

I saw this guy on Youtube with a 4K Onan that was giving him alot of grief, running and stopping soon after.  He stated had taken it to a few repair places with no luck.....He stated that the problem turned out being was the oil was slightly over filled from the 1.6 qt that is required and that on the dip stick the oil should be not past the add on the dip stick.  His symptom was it ran and died soon after.  I am not sure put have you repulled the plug to make sure it is not slightly wet from overfilling?  The only reason my non-motor headed way of thinking even chimed in was it sounds like you are ready for comments from the peanut gallery as to most of the smart answers have already been provided.

https://www.youtube.com/watch?v=vzXDlln8aUw

 

[bigguyone]

Yes I have check oil levels, I even drained. It and refill. I think I mite have found out what it mite be. I took the long bolt holding the  flywheel out, I saw the key had bent over just enough to allow the wheel to move just a little bit, so I'm thinking its putting the timing off just enough to run but was not able to keep up with demand once it was loaded up.  As long as it was a small load it keep up, but the more load it just couldn't keep up. So getting a new key for it and see what it will do. I don't know how it got off...? will post when I get it done...?..