Onan LP Generator Problem UPDATE with new ?

[cahner]

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

[Sam_Spade]

Kayteg1 wrote:

Sam Spade wrote:

Kayteg1 wrote:

If the generator restarts after like 20 minutes and runs fine for next few minutes - that would confirm it.

That would tend to confirm a fuel restriction of some kind.....including maybe a regulator failure.

Yes,
frozen tank = low pressure = fuel restriction or starvation.

Sigh. But that is not the ONLY thing that can cause low pressure and fuel starvation. Fuel starvation does NOT automatically mean a freeze up somewhere.

[Kayteg1]

Sam Spade wrote:

Kayteg1 wrote:

If the generator restarts after like 20 minutes and runs fine for next few minutes - that would confirm it.

That would tend to confirm a fuel restriction of some kind.....including maybe a regulator failure.

Yes,
frozen tank = low pressure = fuel restriction or starvation.

[wolfe10]

MEXICOWANDERER wrote:
You would need a LIQUID suction line and pots only have vapor valves. A permanent horizontal tank might have a liquid line. Unheated a liquid line would freeze in a minute or two.

As I recall, the liquid line on the Onan Liquid LP generator runs several loops over the exhaust manifold before entering the on-generator regulator.

[Sam_Spade]

Kayteg1 wrote:

If the generator restarts after like 20 minutes and runs fine for next few minutes - that would confirm it.

That would tend to confirm a fuel restriction of some kind.....including maybe a regulator failure.

[MEXICOWANDERER]

You would need a LIQUID suction line and pots only have vapor valves. A permanent horizontal tank might have a liquid line. Unheated a liquid line would freeze in a minute or two.

[Kayteg1]

Liquid gas feed is not the same what liquid running.
All propane systems have vaporizer.
When for normal use the tank works as one well, high draw like engine can froze the tank and that is why it draws liquid from tank, when vaporizer is mounted on the engine.
Air cooled engines simply have LPG metal tubing zigzagging over engine head.
I still think OP has tank freeze.
Maybe not to degree to have ice on it, but to degree that pressure drops and engine dies.
If the generator restarts after like 20 minutes and runs fine for next few minutes - that would confirm it.

[wolfe10]

Yes, some Onan LP generators did receive LIQUID LP and it was converter to a low pressure gas in the generator itself. Had one in our 1993 Foretravel. Converted it to high pressure vapor. Eliminated the on-generator regulator clogging.

[MEXICOWANDERER]

What it could do but not likely with an air cooled engine...

Run liquid through a vaporizer heated by water...

Small engines run on vapor so the "running out of fuel due to a hole" does not compute.

These engines also have a "safety" either an electric solenoid unlikely, or a vacuum switch (likely).

[Sam_Spade]

dirtroad2 wrote:
I to have a onan LP generator but mine runs on liquid propane not vapor.

I don't think you understand the situation correctly.
I'm sure that it doesn't "RUN" on liquid propane.

[dirtroad2]

I had a problem simaler to this. I to have a onan LP generator but mine runs on liquid propane not vapor. All my LP appliances worked but my generator would not run unless my Lp tank was above 3/4 full.When the tank got a round the 3/4 level the generator would starve for fuel. It turned out the liquid tube in the LP tank had a hloe in it and would not pull liquid LP through the tube once the LP level fell below the hole

[MEXICOWANDERER]

LPG screams for enough vaporization area. Before you do anything else, heat the jug with a heater. Do it slowly. Heat the tank to around 100F.

Now start it and load it. Has the run time before shutdown increaaed a lot? If so you need a horizontal not vertical tank.

Lots and lots of boiling water slowly will heat the liquidified gas. I prefer electric heat set under the tank a foot distant.

[azrving]

Engines need 3 things basically.

1. Compression- Unlikely problem for your gen but I have worked on small engines that had exhaust valves stick when hot. Gas engines with deposits.

2. Ignition- doesn't sound like yours but cant be ruled out until proven. Ignition problem usually but not always is more of a on/off condition.

3. Fuel supply- sounds closest to your problem. Lean fuel= surging, sputtering, loping, hunting, stalling, low power, white spark plug or very light color. Rich= blubbering, soot or black smoke with a gasoline engine, low power, fuel smell, black or dark colored spark plug.

Most small engine problems are fuel related. It doesn't mean that's what is wrong with yours.

[cahner]

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.

[Kayteg1]

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?

[azrving]

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.