Can I cut off my Onan regulator vent hose to blow out dauber nest, then replace

Hi folks, I have a 2004 Freightliner Sprinter RV with an Onan Propane Microlite 2500 Generator. The prior owner had the generator serviced about a year ago,....and the battery is fairly new.  It spins over or cranks very well, but does not fire or start.  I suspect that the regulator vent line is clogged with a mud dauber nest.  I have read that the tube should not be cut off...?.but wondering if the tube could be cut off, cleaned out, then reinstalled with a properly sized brass dual hose barb.  I cant imagine this would not work, unless the restriction of the slightly smaller diameter of the hose barb was somehow enough to create an issue in the proper air flow in the vent line.

Can you run a wire up the vent tube to see if it's clear? That would likely break up any nest it hit as well. If the tube is soft enough, gently squeezing along the length with a pair of pliers would also break up a nest so the pieces can be knocked out.

There s/b a "sock" over the end of the vent hose to prevent bugs from getting in there.  If it is missing, I highly recommend you get (or make) a replacement.  I believe this is the correct part.  As for cutting off, it appears this hose is called the 'pressure balance' hose and must be a specific length, although I'm not sure since the 2.5KW unit uses low pressure LP and does not have an actual regulator.  Here's a link to a service manual, although, the 2.5KW model isn't well addressed, at least, I didn't find it.  But, look beginning at page 8-23 for LP fueled units.  It appears the vent tube connects to the carburetor.  You may be able to disconnect it there and blow it out.


That said, I just had a similar starting problem.  I religiously started my generator every month over the winter.  But then, when I finally de-winterized and tried to start it, it would just crank and crank.  It turned out to be the little spring on the choke butterfly shaft.  It is supposed to return the choke to full choke when the engine is not running.  There is a vacuum diaphragm that pulls the choke open when it starts.  The spring had come loose and was not closing the choke.  I could manually close the choke and the generator would start right up and run fine after that.  I was able to reattach the spring and that fixed the problem.  The photo shows the springs circled in red.


Caution: Do not attempt to remove the carburetor to do this.  The throttle linkage cannot be disconnected and reconnected with the cover still on the unit.  The only way to do this is to drop the generator out from under the RV so you can remove the cabinet.  This is a VERY expensive operation at Cummins.  Don't ask me how I know.

Yeah, I called Onan yesterday and they quoted me an initial diagnostic fee of $350 and an additional $375 to check and clean the vent line,...?..I couldn't believe it.