RV Onan Propane Generator troubles

[Fox]

Our generator quit working 4.0 BFA 4.0 Gen Set...will start but runs rough and eventually runs out, sputters HELP?!

 

[Racerham]

Hi, and Welcome to the forum!

Propane generators have advantages; the fuel system doesn't gum up with old gasoline, the fuel never gets old, and generally, they run trouble-free for several years.

The disadvantage is that they are harder to troubleshoot, especially when it comes to fuel issues, and the demand valves go bad after a few years leading to the type of trouble you are having.

Your case sounds like a fuel delivery issue.  Rough starting and running, not coming up to speed and quitting soon after starting would be symptoms of a bad demand valve, a low pressure in the fuel line (should be 11" of water column), maybe from a plugged line causing insufficient flow. VERY cold weather (below zero) or an empty tank will cause the same troubles.

Can you check the pressure in the line? some setups have a pressure meter that makes it easy. Is there fuel in the tank? Can you hear or smell fuel flowing when you press the purge button on the demand valve? How do other gas appliances work?

I know this is rather generic troubleshooting hints, but I don't have any specific information on your setup, so can't give any detailed information. Hopefully, others will come along with more ideas for you.

Anyway, Welcome.

HTH

Mike

 

[Lou Schneider]

Also carefully check the condition of the tube running from the regulator to the venturi (where the carburetor would be on a gas engine).  The regulator doesn't send fuel under pressure to the engine, it relies on venturi vacuum pulling on the regulator diaphram to meter the fuel.  No vacuum = no fuel.

Even a small leak in the tube, a loose clamp, etc. can reduce the amount of fuel getting to the engine, making it run lean.

 

[joey]

Absolutely agree with Lou, work on them every week and have seen loose connections or cracked hose create havoc on a propane gen. Also check air filter.

 

[fgruhl]

This lesson cost me $600, but my generator is running good as new now.
Onan propane generators have a small 'vent tube' that ensures that there is a good mixture of gas/air for combustion.  Unfortunately, propane has a sweet smell that tends to attract wasps and yellow jackets.  So they have a preference for building their nests in this vent tube.  If you take a pipe cleaner, you can clear this out.  It's good to secure a small screen over the vent tube to ensure that it remains clear.
I used to have to crank for 15-20 seconds or longer before it lit off.  However, now it starts right up.  The dealer had to drop the generator from my RV before they discovered this.  If the screen doesn't work at some point, I now know what to do.