Gascolator Screen

[N223JH]

Above is photo of screen from my gascolator after 20 hours of engine operation. I don't know if this is the cause of my engine power loss but I believe it qualifies as a "smoking gun." (That story was recounted in thread "Two Fuel Problems.") The accumulation is directly in front of the outlet to the engine-driven fuel pump. No other anomalies were found in a thorough inspection of fuel and electrical systems, including extensive ground running.

The spot seen on the screen consisted mostly of very short, very fine fibers, which appeared to be synthetic inasmuch as they were multi-colored. When examined under microscope, they were *exactly* like the fibers Pete found in his screen after over 100 hours and no power loss. (His posting has a much closer-up image.)

Every ounce of fuel used in this A/C has been run thru a Mr. Funnel. I was, frankly, surprised when I opened the gascolator to see how little filter surface there is with this "donut"-style screen, as compared to the woven brass cylinder screen with which I am familiar.

What is most peculiar is that the accumulation of "lint" was quite thick, 1/8" at the crown of the little hemisphere. It clung quite tightly and required a thumbnail to remove. And...there was no debris anywhere else in the screen. I will leave it to the hydraulic engineers among you to provide the answer, but my guess is that the design of this gascolator results in a direct pull in the immediate vicinity of the outlet port. If you have been inside the unit, you've seen the screen sits on a little ledge maybe 3/16" above the port.

I don't wish to start a controversy because there are perhaps thousands of planes flying--trouble-free-- with this gascolator...and this may have had nothing to do with my power loss on takeoff. But I will be inspecting that screen often, between oil changes, at least until I see a cessation of lint accumulation. (Shoot, I need the safety-wiring practice anyway.) Anybody got an easy retrofit of a conventional gascolator for the 12?
YMMV

Jim in South Texas
#120264

 

[Kyle Boatright]

I had red shop towel fuzz in my screen after 5 hour or so. No doubt it came from the red shop towels I used to wipe things down while building my fuel tanks. Never had any fuel flow problems, though and when I pulled the fuel-pick-ups for the SB several years ago, no fuzz had accumulated around them.

 

[noelf]

I had the exact same thing on my -6A ...

...show up on my gascolator screen during Phase I flight test. Tach time was about 5 hours when I opened up everything to check stuff.

When I built the tanks, fabricated and routed fuel lines, installed all fuel related items, I meticulously cleaned and sealed all fuel items as I went along.

Prior to first flight, I performed the fuel flow test using both tanks, and afterwords ran about 10 gal through each tank using the electric boost pump. I then opened up the gascolator and all looked good, the screen was clean. I do not know where this stuff came from, but my first guess was a spider web. The texture of the "whisker material" was not what I thought a spider web would be (altered by 100LL??), so I have no idea what it really is. The next 25 hour gascolator screen inspection was clean.

 

[Geico266]

You indicated you inspected the firewall forward fuel system right? Did you find anything in the carb bowls? Needle valves?

Did you flush the fuel tank after getting the plumbing done? I cleaned the fuel tank by filling it with 20 gallons (during tank calibration) then I removed the quick drain and used the electric fuel pump to force fuel out faster. I drained it into a MR. Funnel looking for stuff. There was "construction debris" in the Mr. Funnel so I kept adding fuel and draining it to flush the tank. I kept going 4-5 times until there was no debris.

The material looks like the "stuff" left over from Scotch Brite pads when cleaning stuff?

 

[Jack Tyler]

Related question, please...

For the RV-12 fuel system, is this mesh screen the only onboard filtering the fuel sees before hitting the carbs? If so, I can see why folks are funnel-filtering their fuel.

Just an aside: U.S. boat builders universally used a similar approach by using fuel supply standpipes in their fuel tanks which had a similar screen mesh over the pipe end - to 'screen' the fuel. Of course, the tank may then be buried in the boat somewhere with insufficient overhead clearance to remove the standpipe...which becomes necessary when debris in the fuel clogs the screen and starves the engine. That's why they all gave up that practice several decades ago and rely on downstream filtering.

Jack

 

[Tony_T]

Screen debris

For the RV-12 fuel system, is this mesh screen the only onboard filtering the fuel sees before hitting the carbs? If so, I can see why folks are funnel-filtering their fuel.

Jack

Jack, yes the screen is the only filter.

Larry, I agree that the debris looks like scotchbrite. I had my bottom cowl off to remote the oil pressure sender and decided to pull of the gascolator bowl and check the screen at 57 total hours. The bowl had been off before prior to first flight but not since then. Found was a screen that looks exactly like those pictured in the thread by others although in my case the build up was not enough to cause fuel pressure problems:

I had sloshed out my tank with a couple gallons of fuel after testing it and had run a couple more gallons thru to check fuel flow per the PAP, but apparently there was still stuff in there.

Based on what others have found and what I have experienced, it would be prudent to check the screen at short intervals after 1st flight. I anticipate the debris will not be significant at my next check.

Tony