If you're using a 'certified' a/c gascolator, there's a big risk of the rubber parts disintegrating in even low % gasohol. I've had it happen to me (too young & dumb at the time to check for ethanol in the gas).

Qualification: I'm a long way from flying; I'm working on the fuel system components now.

I rejected the disc type filters for the reasons others have mentioned: too little capacity. I considered the big remote oil filter-looking one, but it just looked big & heavy in the pics. After a long search, I ended up buying what's been proven to work: What Ed Did.
From Ed's web site:



Here's what Ed sent me (Thanks Ed):
>>
Fuel Filters:          OEM Auto Fuel Injector Fuel Filters (Two in Parallel)
Type:             AC GF - 481 Pkg: 25056052 OEM:25055129 (or equivalent)
            Replaced by GF652, NAPA FIL -3481
Fittings:         3/8 Saginaw to AN6 Adapter, "O" ring required

The 3/8" Saginaw to AN6 Adapters took a bit of effort to find - but they are out there.  Good Luck
>>

Now, when I searched the various suppliers, all the specs said that the threads on the filter are M16x1.5. Maybe GM didn't want to deal with telling its US customers that it was using Metric, so they made up the '3/8 Saginaw' name to hide the metric numbers. ;-)

My local NAPA parts house had them in stock for around $15 each; Autozone is around $3 cheaper:
http://www.napaonline.com/Search/Detail.aspx?R=FIL3481_0063493239


Size in inches:  4.29 H x 2.17 OD (roughly the same diameter as the Walbro pump, & a little shorter)

Most of the A/N fitting vendors have M16x1.5 (O-ring in the end) to A/N flare fittings listed, though I haven't managed to find one locally to screw into the filter to check it.
Earls # is 991955:


Ed, does that look right?

Charlie



On 1/19/2011 9:55 AM, Ed Anderson wrote:

Hard to be certain what is causing it Bill.

 

However, the use of ethenaol in gas always raises my concern about its effects of polymers used in fuel hoses and seals.

 

You indicated no/little of the particle in the secondary filter - it could be as you indicated  the small amount being due to lack of much use of the secondary pump  OR it could be it’s a pump failure indication in your primary line and that is why your primary filter is picking up the crud rather than your secondary. 

 

If impending pump failure - I would expect to see a drop in fuel pressure - so the question is whether the drop you were seeing is due to the filter clogging  or the pump failing (possibly both).  The point is that the crud could be coming from someplace other than your pump and simply clogging up the main filter because it’s the one used the most and your pump could be OK. 

 

 

Ed

 

. 

From: Bill Bradburry

Sent: Wednesday, January 19, 2011 12:33 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] MAP table corruption? Nope! fuel filters!

Well, the MAP table was ok.  The problem was my high pressure fuel filter on the primary fuel pump.  There were a lot of black particles in the filter that had it blocked.  The secondary filter was clean but had only been run for a few minutes.  This is the second time I found black material in this filter.  The first time was about 40 gallons ago.  This previous material was somewhat gooey and I thought that it may have come from not properly cleaning my hoses out after I made them.  This time the material looked like tiny black particles.  I don’t think they came from the hoses, but if not, they must have come from the pump itself.

 

My fuel system is ..from the wing tanks: a finger strainer in the outlet of the tank, then to a fuel selector valve, then thru a boost pump, then to a Gascolator, then to either of primary or secondary fuel pump, then a filter after each pump, then fuel rail, then fuel pressure regulator, then excess fuel returns thru the selector valve to the tank I am using from.

 

I haven’t yet checked my finger strainers because they are a bitch to get to, but my Gascolator did not have any of the black particles in it.  It had a small amount of white fuzz that is probably fiberglass dust from my fuel tanks in it.  This leaves me a section of -8 hose about 14 inches long or the fuel pump to be the source of the black particles.  Oh yeah, the finger strainers and the Gascolator are both able to move fuel.  I emptied both tanks of about 15 gal of fuel so that I could try and check the finger strainers.  The boost pump filled a 5 gal can in 2 or 3 minutes pumping thru the strainers and Gascolator.  My fuel lines up to the FI pumps are all either ½ inch or -8 in size.  After the FI pumps the fuel lines go to -6 to the regulator and -4 to return to the tanks.

 

Is anyone else seeing this kind of material in their filters?

 

Also, since this occurred with about a tank of gas since I last cleaned the filters, I am concerned about the capacity of the fuel filters I am using.  I am using Summit filters like the one here.

 

http://www.summitracing.com/parts/SUM-230105/

 

This filter has a small screen that is about ¾ inch in diameter and is 40 microns, so when it gets very little contamination, it plugs.  I am thinking it would be fine for a drag car, but not for hours of flight unless your system was so clean you didn’t need it in the first place.

 

I originally had one filter in the system, but became concerned and added another one.  Now I am wondering if I should go to the type of filter that looks like an oil filter and if I do, would one be sufficient or should I try and put in two filters of that type.  I have very little space to add this type of filter and I don’t know if it would even be possible to add two of them.  I would really appreciate any input you guys could give and possibly some pics of your installation if you are using the oil filter type.  Do these type have the capacity to flow fuel when they get contaminated or will they block like these small in line filters?

 

Fuel starvation is a major cause of experimental plane crashes and I am close enough to be thinking of flying.  :>)    Hep me!  Hep me!

 

Bill B

 

---

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Bradburry
Sent: Sunday, January 16, 2011 5:24 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Apex seals and MAP table corruption?

 

I may be taking it back what I said about the MAP table.  During my runup today, I noticed that the fuel pressure was dropping.  At full WOT, the pressure dropped to below 20 psi.  I engaged the secondary fuel pump and the pressure came back to the 40 lb range.  It appears that my fuel filter after the primary pump may be partially clogged.  I will clean them tomorrow and let you know what I find.

 

Bill B