Uh-oh, while practicing emergency descents in my PA-22-150....

[Jaysmiths]

About a month ago, while flying down low looking at a field out in in the country, had some sputtering and rough running. Yikes, changed to the right tank and started looking for a place to put it down. It smoothed out after 30 seconds or so, I flew home, no longer in the mood to look at fields.

OTG, sumped the tanks, found a small amount of water, put her in the hangar and thought that must have been the problem. Couple of weeks later, flew around the pattern a couple of times, no issues.

Today, flew over to 4M3 for some 100ll, filled her up, then climbed to 3500 AGL to practice an emergency descent. On spiralling down, no sputters, no issues at all. After doing a touch and go, climbed back up, did some steep turns first on right tank, then switched to left....a couple of minutes or so later, sputtering returned, this time really running rough, perhaps some popping (hard to tell for sure with the headset on). So I went into another emergency descent, this time with more urgency! Switched to the right tank, landed long but got stopped before running out of pavement. About the time I started taxiing, engine smoothed back out!

I borrowed chocks from a cropdusting service there, powered her up to 2000 rpm on both left and right tanks, she ran fine. With some trepidation, took off and climbed to 5000, still at the airport "just in case' and she ran fine so nervously pointed the nose for home, about 20 miles away. No issues, no sputtering.

Both times the sputtering happened it was on the left tank. Today there was no water in the tank although there has been a little on from time to time, I guess my fuel cap on that side may let some rainwater in--she does stay outside after flights for a day or two (to let the belly oil drip off into the grass!) and it rains fairly often here.

Any thoughts on this would be appreciated. Intermittent magneto issues? Water in the tank that is only going through the system when turning?

What say ye?

Thanks in advance,

Jay

[Gilbert Pierce]

Select the left tank, put a bucket or can under you gas collator and open the drain valve. It should piss a solid stream.
Is your fuel selector valve detent good, does the detent have a positive feel. It could be it is not selecting the left tank completely. Check that while draining the tank at the gas collator by rocking the selector back and forth on either side of the detent while watching the fuel flow.

If it’s not that I would start looking for a blockage elsewhere. Drain the fuel in the left tank. I would remove the wing fairing start with the rubber hose between the tank outlet and solid line to the selector valve. Check the tank outlet screen. Others have those blocked wit trash.

Lastly, make sure gas cap vent is open.

see post #9 https://www.shortwingpipers.org/foru...ht=Tank+screen

[FarmerJoe]

What power setting does it seem to happen at? Aircraft attitude? Fuel starvation would tend to happen at higher power settings. If left tank isn't venting properly, it may take time to build up a vacuum that would reduce flow.

[Jaysmiths]

Thanks, this gives me something to go on. I replaced the fuel cap on one side, can't remember which at the moment with a used one from a boneyard, now I'm thinking that maybe it's not venting? Could be trash in the tank too, there is a little rust, etc that comes out in when I sump it too.

I'll check it out and report back.

Thanks again

[Jeff J]

Might not hurt to look inside the tank to make sure nothing is floating around and blocking the outlet.

[Gilbert Pierce]

There is no steel normally in the fuel system. If you are getting rust it’s come from an external source. Stick a magnet in it and see if it is steel. Not likely you will get rust from an airport fuel supply. Anyway, rust in the fuel would effect both tanks, not just the left.

I recently spent way too many hours purging a Champ fuel system of rust that got past the screens into the carb.
It came from the ethanol free fuel supply he was using.

[smcnutt]

Thanks, this gives me something to go on. I replaced the fuel cap on one side, can't remember which at the moment with a used one from a boneyard, now I'm thinking that maybe it's not venting? Could be trash in the tank too, there is a little rust, etc that comes out in when I sump it too.

I'll check it out and report back.

Thanks again

If you suspect the new gas cap you could simply switch them between tanks and see if the problem follows the cap. That would certainly be the easiest check to rule out one possibility. Start simple and work out from there.

We had an issue caused by using 5gal cans. Our situation might have been a bit more severe that what you're seeing.
20130613_125053_resized.jpg
One of the cans apparently had trash (leaves or something) in it that got poured into the tank. We initially tried just sumping the tanks but ended up unscrewing the sump out of the bottom of the wing before we got the trash to come out. Wouldn't suggest doing that with a full tank, rather only leaving a few gallons in there. We used a filter type fuel funnel we got from the autoparts store. It was a little messy pulling the sump drain but just be quick.

Other than this situation, we don't ever get any debris in the sample cup. If you're seeing something I would certainly chase that down.

[PA-16]

Heres an original gas cap, its stamped Eaton, and has two vent holes on the inside and 4 that vent to the outside. Harley and Piper got them from the same store in the 1940-50s. You have to have the vents. There is an AD to drill holes from the side strait into the inside of the dome top of the cap to prevent blocked vents, the 4 air inlets on the bottom edge have been blocked by those large filler neck gaskets some people use, you have to make sure those 4 inlets are not blocked. If you decide you are going to drill the holes in the original Eaton cap, you might try to sell them on ebay first, some of the bike buffs pay a lot to have original equipment on their early Harleys.

Wag Aero sells a repop for 7 bucks, I carry a couple spares https://www.wagaero.com/flange-vented-fuel-cap.html

https://www.ebay.com/itm/original-Harley-Davidson-Eaton-Gas-Cap-Knucklehead-Flathead-Panhead-Shovelhead/143123132230?hash=item2152cdaf46:g:5i0AAOSwHcdcXcM o

[FarmerJoe]

If you suspect the new gas cap you could simply switch them between tanks and see if the problem follows the cap. That would certainly be the easiest check to rule out one possibility. Start simple and work out from there.

We had an issue caused by using 5gal cans. Our situation might have been a bit more severe that what you're seeing.
20130613_125053_resized.jpg
One of the cans apparently had trash (leaves or something) in it that got poured into the tank. We initially tried just sumping the tanks but ended up unscrewing the sump out of the bottom of the wing before we got the trash to come out. Wouldn't suggest doing that with a full tank, rather only leaving a few gallons in there. We used a filter type fuel funnel we got from the autoparts store. It was a little messy pulling the sump drain but just be quick.

Other than this situation, we don't ever get any debris in the sample cup. If you're seeing something I would certainly chase that down.

If you are going to go out, and try to make your airplane quit in flight, stay in the pattern!! I had this discussion with a co-worker as we were taxiing out to do exactly that!!

[at7615]

https://www.ebay.com/itm/Hopkins-Mr-...rd!72938!US!-1

If you use gas cans, get this or something similar, or at the very least use cheesecloth!