When I was bringing my new 180C home fuel would burn out of the left tank much more than the right. It would even burn fuel out of the left tank when the selector was set to the right tank. Also I noticed a slight suction on the right tank when opening cap to refuel.

First, I switched the caps side to side with no difference.

Next I adjusted the fuel vent behind left strut to factory recommended measurements. It was lower than it was supposed to be by about 1/4". This made the suction problem worse! Suction in both tanks.

The plane had a new right bladder installed and the fuel selector overhauled two years ago. Vent tube seems to be clear as a little fuel will come out of it when tanks are fairly full and I turn hard right on the ground.

I'm thinking new caps to be sure they vent and move vent tube back lower like it was. I'd appreciate any other ideas of things to check or do. This makes me nervous as I don't want to be flying a glider.

Thanks for any help!

Had a 185 awhile ago that did the same thing . Never did figure out why . On a long x country it seemed to burn down to about 1/2 tank or less on left tank then it would start using the other side . Never became a glider . Just gave me something to ponder while cruising along. My old 180 did it as well , just not as much .

I had a problem on my 182 so bad it would collapse the right side and push the fuel out the left vent against the airstream at cruise at a high rate. It was a pain in the ass to get the bladder hooks back on each time. I adjusted the vent to the Cessna spec, and it fixed the collapse problem but still fed unevenly at cruise. I made a couple of adjustments of the vent downward in 1/8 inch increments until the feed rate was even from both tanks.

Check the right finger strainer. It likely got twisted during the new tank install and is not allowing fuel to flow as freely as the left. Since the tanks are tied together with the vent line, the much better flowing left tank is sucking on the right tank (vacuum effect).

If this proves to be the case, replace both strainers (I can't remember what year 180 you bought but I think you'll get lucky and have two single pickup point just fwd of the zipper in your headliner). Use these ones from Burls, the photo depicts ones for an Aeronca Sedan or some such… but you get the point. The C180 strainers are such a work of art I almost hated to put it inside the fuel tank


Incidentally, I discovered these when a similar scenario to yours occurred to me after a bladder replacement. Several mechanics suggested that that was 'just a Cessna thing' …. But running a bunch of gas through it (such as on take off) I could flip the fuel selector back and fourth and discover (on the engine analyzer) that the left tank was only capable of lowing something like 14 gph, while the right would flow 25+. I think one or two take offs with the selector inadvertently left on the left tank would be all it took to be shopping for a new top end (or worse).
Hooray for engine analyzers! With what some of these engines cost, I can't imagine having that technology so readily available and still flying with the old pull it till it stumbles routine.

Take care, Rob

On my 59' always had the same issue. Done everything except what Rob mentioned and will look into that. However, there is good/even flow out of both tanks. We have gone through the whole system finding everything to be up to spec, even replaced the fuel selector at last annual $$$.

After filling up full tanks it always burns out of left first (according to stock gauge), even with the selector on right tank. No matter what, the tanks cross feed (transferring to the right) and I get the suction you talk about too. Just shy of 2000 hours flying it that way and never a burble in the fuel flow. I just leave it on both all the time now.

Jacked with the vent tube a lot trying to find the sweet spot. Had Willie Stene adjust it last summer when we installed the Sportsman, and he got it the best it's been, but I always get a little blow by out of the vent and onto the wing. Always within .5 gallon on the fuel totalizer at fillup, so I just wipe the wing and fly-on. Not sayin you shouldn't look into it further, but I've gone down the rabbit hole trying to fix the fuel transfer/venting issue and have not been able to "cure" these symptoms...

Also, due to this pressurizing of the tanks, get erroneous readings below half tanks on the stock electric fuel gauges, giving low readings. Early on I installed a JPI 450 fuel flow b/c the stock gauges are just not accurate. Doing a lot of XC, it sucks to land thinking you need fuel (that your losing fuel rapidly?) and then watching the gauges go to half tanks upon landing or just slowing down to landing speed...Anyway, if you find a solution let us know!

I'll try to find a link to a write-up on this by Cessna Pilots association, or some group like that, which details the why's and how's of this issue.

Plus 1 on the Burl's---I have one and think it installs easier too.

Thanks for the replies. I've moved the vent back to where it was so I won't have a big vacuum on the tanks. Also took fuel caps apart to be sure they weren't clogged. I have a call in to Burls to get more info on the strainers. Hopefully this is a minor deal and can be fixed by going through the fuel system. Thanks again

BTV, does your left vent burble away after you land too? My 180 also sucks the left tank down a bit faster then the right. Never noticed a vacuum on the caps, but the left vent always burble away for a bit after landing. Not sure if it's because the tanks are evening out or what causes it...

I had the same problem on my C180B; I replaced the left fuel tank vent line with a McFarlane vent line:

http://www.mcfarlane-aviation.com/Produ ... %20Number&

which has an upswept portion, and adjusted the vent to the Cessna specification; no more wing stains and fuel feed is pretty close to equal.

HTH, Ron

A1Skinner wrote:BTV, does your left vent burble away after you land too? My 180 also sucks the left tank down a bit faster then the right. Never noticed a vacuum on the caps, but the left vent always burble away for a bit after landing. Not sure if it's because the tanks are evening out or what causes it...

Yes it did burble after I landed. Stopped when I opened the left gas cap and relieved the suction. Immediately went and opened right gas cap and it had a little suction as well. I didn't have this problem until I adjusted the vent tube height to factory recommended settings (higher than it had been).

I moved the vent back down where it was. I figure better to have positive pressure in tanks than negative and possibly not have enough fuel flow.

I've still got the snorkle vent out the top of the cabin that tee's into a cross line that connects the two tanks. Never had all the problems that the behind the lift strut vents seem to have. BTV, your two tanks still have the interconnect don't they. I don't see how you could relieve the vacuum on one side and not the other. I like my above vent but guess if I replace the left tank I'll have to install a behind the strut "problem type".

I once recovered a 180 from a paddock following a series of engine failures, the owner said it ran fine on the ground but kept stopping after a short while in the air. Turns out the bladder was recently replaced and I fished out a full roll of tank tape, a couple pieces of 4 x 2 timber and a length of aluminium tube. The fuel had dissolved the tape adhesive and loose ends were blocking the outlets. The maintenance shop was a little red faced. I always have a second set of eyes check a fuel tank before closing...

Interestingly, the very experienced owner hadn't thought to change tanks when the engine quit.. 3 times...

Experiment with the vent tube location and make sure the cap vents are open. You should never have suction when opening the caps. Put some vinyl tube over the vent and blow into it, check the caps are venting easily

My tanks have the interconnect. I put a hose over the vent and blew through it today. Could hear air coming through each tank with the cap off. Took the caps apart and they are clean and in good shape.

I have found the procedure to check fuel valve for problems and uneven flow from tanks. It is next on my list.

Here's a link, although about 182's, that gives a description about the uneven fuel feeding issue:

http://www.cessna.org/buyers-guide-182-excerpts

180Marty wrote:I've still got the snorkle vent out the top of the cabin that tee's into a cross line that connects the two tanks. Never had all the problems that the behind the lift strut vents seem to have...... I like my above vent but guess if I replace the left tank I'll have to install a behind the strut "problem type".

My 53 model has the original up-top vent also. Like Marty says, these don't seem to give the problems that the later lower vents do. That bit about revamping the vent if the RH bladder is replaced...the previous owner of my airplane mentioned that too. Is that an AD, a SB, or just what? Seems silly, after all "if it's not broke don't fix it". I believe Cessna changed to the low vent in 1956 to prevent icing over, but I dunno if that was ever actually a problem with the up top vent or a solution to a just-in-case situation.

Rob wrote:...replace both strainers (I can't remember what year 180 you bought but I think you'll get lucky and have two single pickup point just fwd of the zipper in your headliner). ....

I believe Cessna went to dual fuel tank outlets in the C180 starting in 1962.

Hotrod, for us it is the left bladder that needs to have a vent nipple up high forward left and then the vent tubing in the wing to the left strut. When I replaced my right bladder with an Eagle a few years ago, I decided that the job wasn't too bad and thought about the left since it has to be ancient. They said they couldn't send one out the door without the new vent nipple for legal purposes. What bugs me is look at a Cessna 195 and 170---vent out the top. I think Bellanca Scouts have a vent out the top and they put a streamline deal in front of the vent to block the ice and rain.

It sounds like the OP has some issues with the fuel system. A bit of asymmetric fuel feeding is pretty common, but you should NOT have a vacuum on a tank, like ever.

The reason the later Cessnas had the underwing vent tube located behind the strut was for ice protection. In my experience, if you're in that much icing, you've got a lot of problems. We typically tweaked the vents on our Cessnas to just a bit lower than Cessna recommends, to get a little more ram air on the vent.

MTV

I have zero Cessna experience but if it were me I'd chase the issue till I was satisfied that it wasn't a safety of flight problem. I flew a plane quite a bit that fed unevenly from each tank. I didn't think it was an issue till it became a glider with one tank still half full. I'm chicken, fuel system issue scare me.

If you are getting suction in the tank, keep an eye on the bladder. The suction will try to collapse the bladder causing folds and wrinkles. Those fuel gauges are not all that reliable either in my experience. Hard to tell if you are cross feeding, or the gage is acting up when you are in the air.