Onan 4k Microlite runs 10 minutes, quits, will start later.
Hey all you Onan experts out there,
I have an Onan Microlite 4000 genset in a 1999 Winnebago. It starts and runs fine but quits after about 10 minutes, under load or no load (maybe a couple minutes less under load). Just before it quits it will sort of miss once or twice and 5 seconds later it shuts down as if on command.
This problem has manifested itself in only the last hour or two of operation time.
Pertinent info:
Model KY-FA/26100H
1250 hours on the Hobbs meter.
Oil is changed regularly. There's less than 50 hours since the last change. Oil level is carefully monitored.
For the last three years I've driven this RV to work out of town and stay in it four days a week and run the genset three nights a week to cook dinner in the summer. In the winter it's run for a couple of hours so the furnace doesn't drain the coach batteries.
The fuel is shared with the chassis engine. The RV is driven 75 miles a week so the fuel is always fresh.
The fuel pump is working verified by disconnecting the hose and starting the unit. It's putting out about an ounce a second. I don't think it's a fuel supply issue. After it quits, disconnecting the hose shows there's fuel in the line and some also drips back out of the carb. nipple.
I changed the spark plug and set the gap to .025".
Recently (before this shutdown problem) there was more than the usual rpm fluctuations along with the voltage apparently since the lights would flicker once in a while. But after changing the plug this seems to have gone away although it's hard to say when running during the day.
From what I have read on the interweb this model doesn't have a low pressure/level sender but I haven't verified this yet. One guy on youtube (who really enjoyed hearing himself talk) said to take a half pint of oil out to trick the sender. This didn't make sense to me but with trepidation I tried it anyway. No luck.
I did find a dead mouse in the bottom of intake side of the cooling system that looked like it died fairly recently. Because of the limited access I can't see if there is a nest blocking air flow. I seems like there isn't very much air flowing out the exit but I don't know how much it should be because I've never had reason to check it before. I think I read that the unit will shut down if the windings overheat. Or does the engine have a sensor to shut it down if it's too hot? After the last shutdown I measured the cylinder near the head with an infrared thermometer and the highest reading I could get was 244 degrees. That seems kind of hot for ten minutes of running in 60 degree ambient air temp.
How long do the brushes last? Is 1250 hours on the clock a lot?
How is that for a data dump?
Does anybody have any clues or advice? HELP! PLEASE!
Lance
Update:
My wife suggested that I use compressed air to back-blow the airway to see if mouse nest stuff could be dislodged (she's a pretty danged smart woman, I don't know why she married me).
Sure enough, a couple bits of mouse bite-sized foam came out. I looked harder and that little bugger had chewed an area of the foam insulation. It looks like I might have to take things apart to clean it out.
I have an Onan Microlite 4000 genset in a 1999 Winnebago. It starts and runs fine but quits after about 10 minutes, under load or no load (maybe a couple minutes less under load). Just before it quits it will sort of miss once or twice and 5 seconds later it shuts down as if on command.
This problem has manifested itself in only the last hour or two of operation time.
Pertinent info:
Model KY-FA/26100H
1250 hours on the Hobbs meter.
Oil is changed regularly. There's less than 50 hours since the last change. Oil level is carefully monitored.
For the last three years I've driven this RV to work out of town and stay in it four days a week and run the genset three nights a week to cook dinner in the summer. In the winter it's run for a couple of hours so the furnace doesn't drain the coach batteries.
The fuel is shared with the chassis engine. The RV is driven 75 miles a week so the fuel is always fresh.
The fuel pump is working verified by disconnecting the hose and starting the unit. It's putting out about an ounce a second. I don't think it's a fuel supply issue. After it quits, disconnecting the hose shows there's fuel in the line and some also drips back out of the carb. nipple.
I changed the spark plug and set the gap to .025".
Recently (before this shutdown problem) there was more than the usual rpm fluctuations along with the voltage apparently since the lights would flicker once in a while. But after changing the plug this seems to have gone away although it's hard to say when running during the day.
From what I have read on the interweb this model doesn't have a low pressure/level sender but I haven't verified this yet. One guy on youtube (who really enjoyed hearing himself talk) said to take a half pint of oil out to trick the sender. This didn't make sense to me but with trepidation I tried it anyway. No luck.
I did find a dead mouse in the bottom of intake side of the cooling system that looked like it died fairly recently. Because of the limited access I can't see if there is a nest blocking air flow. I seems like there isn't very much air flowing out the exit but I don't know how much it should be because I've never had reason to check it before. I think I read that the unit will shut down if the windings overheat. Or does the engine have a sensor to shut it down if it's too hot? After the last shutdown I measured the cylinder near the head with an infrared thermometer and the highest reading I could get was 244 degrees. That seems kind of hot for ten minutes of running in 60 degree ambient air temp.
How long do the brushes last? Is 1250 hours on the clock a lot?
How is that for a data dump?
Does anybody have any clues or advice? HELP! PLEASE!
Lance
Update:
My wife suggested that I use compressed air to back-blow the airway to see if mouse nest stuff could be dislodged (she's a pretty danged smart woman, I don't know why she married me).
Sure enough, a couple bits of mouse bite-sized foam came out. I looked harder and that little bugger had chewed an area of the foam insulation. It looks like I might have to take things apart to clean it out.
