Hey guys,
I just want to understand this system a little better. I have read about the Cessna 180/185 having issues with drainage of tanks back and forth from L to R and vis versa when on an incline or one side is heavy. I was always under the impression based on what I have read and learned that this was an issue with the lack of a fuel tank selector and if your plane has a tank selector, when placed in the off position you do not have the flow of fuel.
If one looks at the schematic for the fuel system for these birds, there is a return line from the accumulator tank back to a line between the tanks. Is this line the real issue for flow between the tanks?
Reason I am asking is I have a fuel tank selector and it still moves fuel between tanks while I am filling the tanks.
Thanks,
Gypsy

I was under the impression that L or R on the fuel selector was the only way to eliminate crossfeeding in these Cessnas. I heard OFF will crossfeed between tanks.

I've never verified because I've never had any reason to need to check. Never been an issue for me.

There is no off position on the tank selector of the 185. The selector is left-both-right. Off is accomplished with a separate valve actuated with a push pull cable control that is located just forward of the tank selector.

When the tanks are full, they can still cross feed across the vent line according to the schematic, but I find that selecting one tank for parking or during refuelling helps reduce if not prevent cross feed.

As a matter of policy, I try to NEVER turn a fuel valve OFF in an operational aircraft. I know, I know, we do have check lists and all, but frankly, it's just too easy to forget, and there have been a number of engine failures right after takeoff, which are often fatals.

And, yes, the 185 will port fuel through the overhead vent line, but only if tanks are fairly full, or on a pretty severe slant.

With any airplane, it's best to park as level as possible or practical.

MTV

Mine does the same thing. As I interpret the drawings in the Maintenance Manual, it can always drain from one tank into the other, regardless of the position of the selector. Kind of annoying, really.

Agree with MTV....fuel selector never off...56 182 just out of Annual...re built the selector with new o rings and my A&P reinstalled...Routing problem...10 hours later the rudder cable had rubbed a hole large enough to allow a slow fuel drip...caught on the hanger floor on next flight...I want the system under head pressure when it’s parked...in my case if I had gone to OFF...I would have learned when the gas stopped flowing ...if your concerned about a full fuel load..top off and wait and re top off..

The standard tank 62 USG useable 185 might just have the ON-OFF switch? Presumably fuel OFF in the event of a forced landing, otherwise always ON.

Filling, and then re filling may not take into account fuel density change with temperature change. Typically a cold fuel refuelling to the brim is likely to cause spillage as the fuel warms in the wing?

180’s have an “off” position, and no shutoff valve, whereas 185’s have a shutoff valve and may have an optional left-right-both selector valve without an “off” position. The 180 selector valve will cross feed in either “both” or “off” positions, but does not cross feed in “left” or “right”, which is the same as the 185, with the exception of not having an “off” position.
From the 185F POH figure 2-3: “place the fuel selector valve in either “left” or “right” to prevent cross feeding”

fredy wrote:…. The 180 selector valve will cross feed in either “both” or “off” positions.....

In my experience, the fuel selector on my 1953 C180 doesn't cross feed in the off position.
I think the one in my old C170 did though.