Onan 4.0 BFA 1R 16020D Gas in oil tank

Started by RenoN8, July 02, 2014, 12:23 AM

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Tried to start generator on my 86 Sunflyer. Ran shortly then stopped. Unscrewed oil cap to check oil level and it overflowed, along with containing heavy gas odor. Any input on what cause could be? Hm?


One of two things, or possibly both.

Usually this can be caused by a bad float needle in the carburetor bowl not sealing properly allowing too much gas getting into the engine. I believe that's covered in the generator manual for your model.. Just need to find out which model it is.

This could also indicative of bad cylinder rings allowing blow by as well.  For this you can check your compression to see if it is within specs.  For the specs you will need to get your generator model number and research it.  I think that if you do the $5 membership here you get access to the manuals that may help you.
Captain of the Ground Ship "Aluminum Goose"
28' Holiday Rambler Imperial 28


A oil and filter change is first step.  I agree with Fredic.  Most likely stuck float needle.

4.0BFA Spec D.  Service manual 900-0337 in Free Manuals area.



Ok! I may get laughed off this site for this but here goes...
I drained the oil and was looking for oil filter. Most of the manuals show filter on front left. Mine has no filter on front left. Some of the other manuals I have come across and a sticker on the genset itself says change filter if so equipped. I have felt around the back of the gen ( as it is not possible to get my head in there to visualize) and can not find a filter. At the risk of being scorned...Does anyone know of another location the filter could be or does it not have one?


I can't help with the filter but do not worry about being scorned or ridiculed for asking what you may think to be a stupid question. This is not one of those forums where you will get laughed at or ridiculed.



Everything I have seen about a BFA says there is a filter.  Does not matter if it was the RV, AUX, or Utility version.
The 4.0 BF version did not have a filter

You have a picture of this beast?  Also a close up of the ID plate.