Onan LP Generator Problem

[rocking67]

I have a 3600 or 3500kw LP generator in my 2006 5th wheel.  We keep our 5th at our mountain property in the Sierra Nevada mountains, at about 5000 foot elevation.  It has been used on a regular basis, at least once a month sometimes twice or more per month.  I have a separate 100lb tank just for the generator.  It has run in the heat of summer and as low as 15 degrees in the snow and winter. 

I ran it for an hour on a Wednesday and we went to the trailer on Friday.  I started it at about midnight and it ran fine until about 4:30 am.  It did not hiccup or bog down,  It just stopped as if it ran out of fuel or when you shut it down.  It turns over and starts, but then immediately shuts down.  Oil is good, nothing different than any other trip.  The regulator is about a year old, the last time the regulator went bad, the generator just runs slow or bogged down.

Any suggestions would be great.  The local dealer said it was the carb.  My only issue is it did not act up, it just shut off.

Thanks.

 

[nbounder]

That kind of thing happens if you run low on oil, (among other reasons).

 

[Greg H.]

How full was your LP tank and how cold was it during the night? 

My Onan 2500 owners manual states: "On cold days the LPG container may have to be kept at least half full to provide the rate of vaporization necessary to keep up with genset fuel demand". 

 

[rocking67]

Tank was just filled.  It has been used in 15 degree weather.  It was only about 35-40 degrees that night.

 

[Icemaker]

Besides having an oil pressure switch it may also have an oil temperature switch..
My Generac has that...

George

 

[Lou Schneider]

The local dealer said it was the carb.

That's interesting - propane generators don't have a carburetor.

If your generator is an Onan, and it only runs as long as you hold down the "start" switch, that means the generator isn't putting out voltage.

All generators will shut down if they lose oil pressure.  Onan goes one step further and shuts off the engine if the generator stops producing voltage.

The most common cause is dirty slip rings in the generator, which blocks the voltage regulator voltage from getting to the generator field windings.  Or it could be a bad voltage regulator board.

 

[rocking67]

Ok.  The main fuel line comes out of the tank, through the regulator, into a round (lack of a better term) piece on top of the generator, then into a "carb" looking item (where the air filter is), obviously the air intake, goes into the heads, intake manifold or valves.  I do not know the flow or how the propane engines are set up.  All the lines look good and do not appear to be leaking.

I will head up with my gas generator to try and check all the parts mentioned.  Unfortunately, there are no good places to get replacement parts, at least not within an hours drive.

Thanks

 

[Foto-n-T]

Although it doesn't sound like it was that cold out, I'm wondering if you froze the regulator. It would be interesting to know if it starts when you go up there again after sitting for a few days.

 

[rocking67]

Lp flowed through the regulator and it is fairly new, I know that does not really mean anything.  But, I have used it continuously, for about 36 hours straight in 15-20 degree weather, snowing and 3 feet of snow on the ground without issue.

 

[Lou Schneider]

Check carefully the condition of the hose connecting the regulator to the venturi.  The vacuum generated by the venturi has to be applied to the regulator to unseat it and let gas flow into the engine and even a tiny leak will reduce or shut off the fuel flow because there won't be enough vacuum to activate the regulator flow.  Although this usually shows up as a failure to fire up during low speed cranking, not while the engine is at speed.

Again, if the engine stops when you release the "start" switch, it's either an oil pressure problem or the generator isn't producing enough voltage.  You can bypass the oil pressure sensor for testing by lifting the lead from it - it's the same screw-in round sensor used in car engines.

 

[rocking67]

Thank you all for the information.  I will let you know what is the final dispo.

 

[Cant Wait]

Had a gen that the low oil pressure switch went bad and acted same as yours, find the sw and try it with the wires disconnected, if no run then, try hooked together, not sure if your oil press switch is normally open or normally closed. If gen runs fine with wires disconnected or with wires hooked together then the switch is your problem