Hello,I have an onan 3600 LP generator. It has only 92 hours on it, very little use by me or the original owner. I originally tried to T into the propane line post crossover regulator and discovered that the gen set was being starved for fuel and ran it off of dedicated bottle. It runs intermittently. Once started it will run the water heater, microwave or AC. After about 20 or 30 minutes is bogs down and will begin to sputter and die. When restarted it will sometimes take the load of the AC and sometimes will not. It will take the load of just the fan without bogging down. Any ideas are welcomed.Thank you, Casey

I have a lp gen set never a problem, but guessing you have carb problems ,clean it and try it.

Sounds a bit like an overheat or low oil condition.Maybe a voltage sensor.I think you need the services of an Onan (Cummins) shop.While it's possible, an LP "carb" doesn't gum up like a gasoline one.

Sounds lean. The one element you mentioned is that you opened the system to try and run the other device. So did it run ok before you did this? If so what did you introduce that caused a problem? A spec of dirt? A metal shard of pipe thread? A piece of teflon tape? When having any problem it's best to first back track.It shouldn't be a regulator problem since the metering adjustment should not have changed and the hours are so low nothing should be gummed or dirty. Without looking at specific models I would assume like most propane equipment it possibly has 2 regulators. One at the tank and one on the generator. Contrary to what many believe propane systems do not inject or provide pressure to inject the fuel. They draw the propane in through the regulator. The primary regulator controls the amount of fuel but the engine regulator diaphragm is pulled on by engine vacuum and then opens a valve to allow propane to be drawn in. Its a safe design that lets the system not malfunction and continuously feed propane.So again, it sounds like you have a lack of fuel and a lean condition. If you had a rich condition you would get more of a blubbering sounding engine. I'm not going to tell you what to do as I dont know you abilities but what I would do is try to prove what the condition is. If I was running the generator and it starts to falter I would use an UNLIT propane torch to introduce a small amount of propane into the air cleaner intake. If the rpm recovers and it smooths out, that would prove that it's not getting enough fuel. When working on any fueled equipment think ahead and have fire extinguishers on hand. Keep the equipment away from buildings or other valuable items.It seems like there is are a good number of people having issues with cheap primary regulators.

First rule that suspected fuel starvation is not the issue. When the generator dies, is propane tank cold or frozen? What are outside temperatures at the time?

Thanks all. I was finally able to get out again this morning. It is in the 50s and. The gen set ran the heater and water heater fine from about 20 minutes. At that point it began stumbling. The bottle was cool as I expected. It was not frozen though. When it died it would restart but would not run, it would stumble until it died.

Onan LP Generator Problem UPDATE with new ? | Good Sam Community

alanmikkelsen
Explorer
Aug 29, 2016
I have the same generator and had problems all last summer. It runs off a dedicated bottle, also. The house bottle (furnace, etc.) ended up having a bad regulator, after I replaced a furnace circuit board (grr). After replacing the regulator on that bottle, I decided I'd replace the regulator on the generator bottle, and guess what? The generator runs fine! Regulators are cheap, you might try putting a new one in. These were about 10 years old and both had failed, apparently.
Sam_Spade
Explorer
Aug 28, 2016
You need to get the hot-restart current draw of your compressor tested.
The A/C may need service OR the gen may be a bit too small.

If the A/C is going bad, getting a bigger gen will just postpone the pain.
cahner
Explorer
Aug 27, 2016
I have everything set up and in place as it is designed with the on demand regulator. The gen set seems to run fine. It handles the load of the AC and water heater easily. After about an hour if the AC turns off it kills the gen set when it restarts. It handles the fan and then dies when the compressor kicks on. It will restart and do the same thing until it cools down completely.

I need your ideas please.
MEXICOWANDERER
Explorer
Aug 03, 2016
I used to pour boiling water over the vaporizer to determine if it is the problem. State law requires a shutdown switch chop gas when the engine fails to run in California. Some are oil pressure activated, others are vacuum activated. The shutdown safety is manually bypassed while cranking.
cahner
Explorer
Aug 03, 2016
Ok, I finally bypassed the KN on demand regulator and ran the fuel from the bottle to the fuel lock off and then directly to the carb. It runs great. The 2 stage regulator that comes off the bottle reduces the pressure to 10 lbs in the first stage and 11" water column in the second stage.

This makes me ask why is the on demand regulator needed, or is it?
cahner
Explorer
Aug 02, 2016
Okay, I played with it a little more tonight. It will start when primed with the prime button and then will run great with the prime button just barely pushed in. When pushed in it is over fueled and will die, when not pushed in a little it is starved. The new kn has a 7/16 office and is a 6 oz regulator

Any ideas?
cahner
Explorer
Aug 01, 2016
I do not believe that a safety is the problem. I bypassed the fuel shutoff and ran directly to the regulator and verified it has oil. I would think the murphy switch would shut it down, as is should, but would not let it continue to run although at lower speeds.

The only way it will continue to run is when the prime button is held in the entire time.
marcsbigfoot20b
Explorer
Jul 30, 2016
I just had the same problem on my Onan 2500LP.
It was hunting under no load and had trouble keeping up when the load was applied.

Used carb spray to verify while it was hunting under no load that it was running lean. A spray and it ran great.

I also have the SD demand regulator. I bought the rebuild kit on Amazon for $68 maybe 4 weeks ago. SD regulator kit
Installed it and it ran perfect, just had to adjust the gov linkage since I had messed with it during trouble shooting.
I think the spec says about 62.5 Hz and 123 volts at no load.
MEXICOWANDERER
Explorer
Jul 30, 2016
Did you verify the SAFETIES are not malfunctioning? LPG engines have either a vacuum or electrical valve fuel cutoff. The electrical usually runs through an oil pressure switch, the vacuum off the carb base port fitting.
cahner
Explorer
Jul 30, 2016
The problem was the regulator diaphragm. The sd regulator is no longer made and had to replace it with a kn model. Got it all hooked up and everything was great. Let it run for about a minute and then put it in the trailer. Now it will not run unless the prime button is held, even then it runs at only about half speed and acts as if it is starved for fuel and dies if prime button is not held. Took it back out and checked to make sure nothing in any of the lines and bypassed fuel shut off.

Now I am really baffled. Any ideas are appreciated.

Thanks,
Casey

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