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Racer_C · 07-12-2021, 12:01 PM

I have an Onan 6500 LPG generator running poorly. I could swear when I tested it in April, it ran fine. Haven’t really used it in the two years since had tune up, and voltage regulator replaced. This past weekend accidentally tried to start Gen with the LPG tank off. I don’t know if that did something to the gen (air in system?), but it runs like garbage now. Clearly not producing the electricity it should be (it barely runs one ac unit). It idles a little while, then it drops to like it’s barely running, wavers, then picks back up. It does this in about 10 sec intervals. LPG working fine for frig, hot water tank, and heater. Will upload audio when have correct file format.

Racer_C · 07-12-2021, 01:47 PM

It sounds like this:

Wadell · 07-12-2021, 02:14 PM

IF it got air in the lines the air should be out really fast. I would visually inspect the regulators and make sure there is not any debris clogging up the vent. A clog on the vent could cause the regulator to not move when needed.

A second possible cause could be some LP tank connectors, IF its a normal tank you are running it from, have a restrictor that if there is too much flow it will move a valve that will restrict the flow. I had this when replacing broken commercial grill tank connectors and the high demand of the large commercial grill flowed too much gas and stopped the flow. Lets say this is the system you have, turning the gas onto an empty line could cause the LP gas to woosh thru the piping can the gimmick restricted the flow. The remedy would be to turn the gas off, remove the regulator from the tank, let the gas bleed from the connector in hand, re connect to the gas, THEN turn the gas on slowly letting the line fill up slowly. Then it should run after that the restrictor was you problem

Racer_C · 07-12-2021, 02:42 PM

Quote:

Originally Posted by Wadell

IF it got air in the lines the air should be out really fast. I would visually inspect the regulators and make sure there is not any debris clogging up the vent. A clog on the vent could cause the regulator to not move when needed.

I am sorry if this sounds stupid, but where are the regulators I should be inspecting? Just because of where we live (mice are a consistent concern and headache), so debris definitely could be a problem. I will post a couple pictures of the generator in a moment. Thank you for your assistance!

Racer_C · 07-12-2021, 02:44 PM

Here are the pictures.

Wadell · 07-12-2021, 04:04 PM

is this running on a large coach mounted tank or portable ones? does the stove work, if that is running off the same tank?

wolfe10 · 07-12-2021, 04:16 PM

Good question about the regulator for the generator.

EASY to tell if it is a LIQUID or VAPOR generator:

Look at your propane tank. Is there a LIQUID tap with line going to the generator? If so, it is a liquid LP generator.

The regulator will be either in the generator housing (hard to service) or in the generator compartment.

OR, it will be fed from the vapor tap on the propane tank.

Let us know. We have had Onan propane generators on two of our coaches. Worked on them so more first hand knowledge than I really wanted.

Wadell · 07-12-2021, 04:31 PM

Racer C, in you first picture, the black line with the white dots looks like the fuel supply. zoomed in looks like the regulator is at the bottom of that. Look at the bottom of that for dirt dobber nest or something covering part of the regulator.

Racer_C · 07-12-2021, 08:13 PM

Big tank attached mid-coach; generator in the front. Attached are two pictures of the tank area. I didn’t test the stove, but I did test the heater, and the frig and hot water heater worked all weekend on propane.

Wadell · 07-12-2021, 08:34 PM

I kinda like your set up there. Easier to get to than mine.

Looking at the tank, I would guess you are getting liquid to the Generator. Is the tank full? IF the tank is running low, and the Generator wants liquid, could be running out. The other pieces, use gas vapor to run and will run fine till the tank is fully empty.

Wadell · 07-12-2021, 09:04 PM

Something else, LP gas is used because it is relatively low pressure, condenses into a liquid, and boils off and keeps a constant pressure. As the tank gets low there is less liquid and as the liquid boils off it gets cold and as the pressure drops the pressure drops it quits pushing the gas. you can put your hands on the tank as the Generator is trying to run, and if its cold mostly at the bottom, you are running out of gas.

Racer_C · 07-12-2021, 09:09 PM

I took a leaf blower to the generator. Nothing. Stove works fine. I looked at air filter, but it looks still brand new. Couldn’t feel anything under the Reg at bottom of black hose with lines.

Racer_C · 07-12-2021, 09:26 PM

Tank is 3/4 full

wolfe10 · 07-13-2021, 08:16 AM

If this is a liquid LP generator with the propane regulator inside the generator (should be able to confirm with Onan/Cummins from the generator model/serial number) it is quite likely that the propane regulator is clogged with some longer-chain hydrocarbons. Almost a light viscosity grease like substance.

The regulator is a common and very good one, but in the Onan, it is oriented on its side to the impurities can not pass through and be burned.

Very likely you will need to remove the generator to access the regulator. They can be overhauled (need the high temp silicone gasket set) or replace it complete.

I would probably do all the other troubleshooting first. Check plugs, wires, etc.