Recently noticed in the Onan 4000 manual that it has a carburetor gas drain valve below the front of the carburetor. The valve is adjusted using a phillips or slotted screwdriver. The gas drains on the front of the generator, but I found that a 1/4" rubber hose fits the drain port. I used a 1 foot hose to drain however an 18" hose would have allowed draining to a container on the ground. I got 1-2 oz of gas out.I had not been doing this before without issue. I run the gen once a month though and put Stabil in the gas.. Now I plan to drain the carb when not using it for awhile as further insurance against getting varnished.Any long term MH storers drain it also?

if you put stabil in why drain? for winter storage just double the dosage and leave the gas in it. Carburetors some times have oring's or gaskets that can dry out when no fuel is present. just my $0.02

Good point on gaskets and Orings, may be a trade off of draining.

stabil is good stuff. cheap insurance and engine is ready when you are.

I would expect Stabil to prevent fuel breakdown but not evaporation. I use Stabil preserved gas in our 5 year old Eu3000IS Honda generator and have for 5 years. I always drain that carb also after use and 4 months may go by before exercising it.

Do you drain the gas out of your Onan Carb? | Good Sam Community

19 Replies

Dusty_R
Explorer
Oct 28, 2015
Thirteen years ago we bought a new mh with the 4000 watt generator. I located the electric fuel on it and put a switch ahead of the pump. So then come fall when I used the generator for the last time, I would turn the pump off and let the generator burn all the fuel in the carburetor.
I like the idea of the drain on the carburetor but will the gas in the jets drain? If not will that very small amount of gas gum up the jet?
We just replaced that 2003 mh for a new 2015, and it also has the carburetor drain. How long has Onan been putting that drain on the carburetor?

Dusty
Cobra21
Explorer
Oct 28, 2015
I don't think the fuel evaporates very fast during a Minnesota winter, but Florida is most likely a different story. I don' drain.
Brian
jjrbus
Explorer
Oct 28, 2015
If using stabil and running occasionally no need to drain. If not using and you want, take a small amount of gas with Stabil in it in an open container and see how long it takes to evaporate. Then look at the film that is left in the container.

Next check and see how much it will cost to clean/rebuild your Onan carburetor. Your choice weather to drain or not.

I drain for storage. Jim
Robocop
Explorer
Oct 28, 2015
j-d wrote:
Exercise, StaBil, No Draining.

X2.

Going on 5 years no issues.
j-d
Explorer II
Oct 28, 2015
Exercise, StaBil, No Draining.
RambleOnNW
Explorer II
Oct 28, 2015
I would expect Stabil to prevent fuel breakdown but not evaporation. I use Stabil preserved gas in our 5 year old Eu3000IS Honda generator and have for 5 years. I always drain that carb also after use and 4 months may go by before exercising it.
lc0338
Explorer
Oct 28, 2015
stabil is good stuff. cheap insurance and engine is ready when you are.
RambleOnNW
Explorer II
Oct 28, 2015
Good point on gaskets and Orings, may be a trade off of draining.
lc0338
Explorer
Oct 27, 2015
if you put stabil in why drain? for winter storage just double the dosage and leave the gas in it. Carburetors some times have oring's or gaskets that can dry out when no fuel is present. just my $0.02

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Do you drain the gas out of your Onan Carb?

19 Replies

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