Sticky Gas - What the Heck??

N962GT

Active Member
Joined
Oct 25, 2020
Messages
134
Location
orig Northville, Mich
Aircraft
YG4 Air Command Tandem
Total Flight Time
800 hrs
SO I flew 1:38 averaging 71 MPH (GPS) up to Wadesboro a couple of weekends back, hung out for a couple of hours, jumped in the gyro and taxiied down to the ramp to top up the front tank with 4-5 gallons of 100LL. Strapped in, took off and flew 1:23 back to CUB averaging 79 MPH (GPS). Made it back 1 minute before sunset. Parked the gyro, went home.

Yesterday I went out to the airport, cleaned off the bugs, did a decent pre-flight, still had 5-1/2 gal of gas in the rear tank so I hopped in and hit the starter. (My front tank feeds the rear tank, from there it goes through the gascolator and on into the carbs).

Now understand that every single time since I installed this engine in 2019 it has started on the first kick, even the very first time after sitting for years before the transplant was completed. This time, nada, zip, zilch. No matter what I did it would not catch. Pulled the intake cover off, turned the key on so the fuel pump was running and watched fuel pour out of two of the carbs. Two floats were stuck open.

Pulled the plugs and only one was wet. Drained the fuel with a jiggler, got gas all over my one hand. As it evaporated a very sticky residue was left behind all over my hand. Gas would not cut it. Go Joe had a hard time stripping it off, but eventually got my hands clean. Drained the gascolator, nothing much in there to write home about.

Put in a fresh load of gas, and eventually got the thing to start, clear, and run so I could fly. Which I did, staying in the pattern for an hour to try to clear the pipes. Seemed to run fine. Then, as the sun set, I did one last TO and the engine lost 1000 RPMs as I climbed out. The AFR showed too lean, into the 15's. Oh, well. I have two more carb racks, and a new set of jets to install anyways as I begin tuning for more HP with the new O2 AFR set up.

But what the hell was that crap in my fuel? And how did it get there?
 
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N962GT

Active Member
Joined
Oct 25, 2020
Messages
134
Location
orig Northville, Mich
Aircraft
YG4 Air Command Tandem
Total Flight Time
800 hrs
The fuel cells are rotational-molded plastic seat tanks popular for decades without problems, it's not the tanks.

Searched the web for ideas, came across the use of styrofoam for making napalm so I put a little gas in a small glass bowl and tossed in a few packing peanuts. They started dissolving instantly and were completely gone in seconds. Picked up a bit of the goo with my fingers before it was completely dissolved and it was similar to what I found yesterday, though that stuff seemed stickier. BTW, sugar does not dissolve in gasoline, the web said that's a debunked myth but I went ahead and tested it anyway just to see for myself and nope, sugar did not dissolve.
 

querist

Active Member
Joined
Oct 10, 2022
Messages
356
Location
Longview, Texas, USA
The fuel cells are rotational-molded plastic seat tanks popular for decades without problems, it's not the tanks.

Searched the web for ideas, came across the use of styrofoam for making napalm so I put a little gas in a small glass bowl and tossed in a few packing peanuts. They started dissolving instantly and were completely gone in seconds. Picked up a bit of the goo with my fingers before it was completely dissolved and it was similar to what I found yesterday, though that stuff seemed stickier. BTW, sugar does not dissolve in gasoline, the web said that's a debunked myth but I went ahead and tested it anyway just to see for myself and nope, sugar did not dissolve.
I never did investigate the sugar thing, so thanks for setting me straight on that one. It can still mess up your engine, but not in the way described in the original post.

Yep, polystyrene will dissolve quickly in petroleum products - learned that one the hard way as a kid.

(Chemistry was over 30 years ago...)
 

querist

Active Member
Joined
Oct 10, 2022
Messages
356
Location
Longview, Texas, USA
Did you save the stick residue? I think you could send it off to a lab to find out what it is.
I'm actually curious now... and I have access to labs at two different universities (one where I teach and one where my son is working on his PhD). My son could do the analysis himself (he's a chemist). I'd need help.
 

Aerofoam

Active Member
Joined
Dec 2, 2020
Messages
364
Location
Az.
Aircraft
Pteradactyl, AC 447/503, too many UAVs
Total Flight Time
Over 3k....(From the ground !)
Yep, polystyrene will dissolve quickly in petroleum products - learned that one the hard way as a kid.
This is actually a composite technique, carve a plug mold (Wheel pant for instance) from styrofoam, laminate it with fiberglass, or carbon fiber and epoxy resin.
After it cures, cut a hole in the skin and pour in gasoline to dissolve the plug mold.
 
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