PDA

View Full Version : Worm in my fuel system


frankh
04-25-2009, 01:36 PM
Hi Guys,

As you know I am the driving force behind the wingroot fuel pump system. Yesterday I had my first issue.

I thought I had a failed fuel pump after takeoff fom Hillsboro airport in Oregon. No problem as the sytem is designed with two independant fuel sources so I flew the half hour home on the one good pump. I climbed to 7500ft as this put in me gliding range of an airport for all of about 5 minutes on the trip and I loaded the tower/CTAF freq of each airport as I had it made dead stick if I had to.

Anway..I removed the fuel filter upstream of the offending pump and voila, the issue was a plugged filter from a length of proseal that had had flaked off, looked like where I had prosealed on the cover as it had that shape.

Interesting to me was that this "worm" of proseal was enough to plug the filter.

I remember I had changed to this sintered bronze in line filter at the same time I started using an E10 (ethanol blend) auto fuel. I was a little concerned at the time because the filter was much smaller than the paper disposable type I had been using before and the bronze element went almost up to the incoming tube of the filter housing..Good enough for fine particles, but not enough room to allow for a worm to enter the filter housing..I,e the worm really plugged the 3/8ths tube ahead instead of the filter itself.

So I am considering changing back to the paper disposable type...I only changed to the sintered bronze type because I read somewhere that water could cause a paper element to swell and cut off the fuel flow.

I can't seem to find a SB filter that has both lots of filter area and plenty of room to accomodate a worm (unless anyone can tell me where to get one) that will fit in the wingroot with all the other stuff.

So The next best thing is I am going to declare an experiment..Namely I am going to take the pair of old paper element filters that I kept and drop them into a bucket of water overnight and see if the pressure drop thru the filter goes up significantly. I will test the PD by the highly accurate method of blowing through the filter..:)


Any helpful comments..By which I mean not those like "You've modified the fuel system so your surely going to die" type coments are welcome..:)

Frank

Walt
04-25-2009, 02:17 PM
I would have thought the strainer on the fuel pick up in the tank would have caught something like this (assuming you are using one). I used the one that van's sells as they have about a 2" screen on the end that would stop big stuff but allows plenty of additional area to let the fuel keep flowing. :confused:

Ron Lee
04-25-2009, 02:26 PM
What Walt said. Please provide a better description of the in-tank screen if any and a picture of the proseal plug.

frankh
04-25-2009, 04:33 PM
I have flop tubes in both tanks which have 1/8th holes in the brass weights from memory.

Its amazing that a worm would find its way through those holes but it clearly did.

Frank

frankh
04-25-2009, 04:37 PM
I just looked at and it looks to be 1/16th in diameter and about 5 inches long..Clearly it bundled up into a ball as it couldn't enter the filter.

Frank

az_gila
04-25-2009, 05:52 PM
...fuel pre-filter might help before your sintered bronze one?

It's a screen type, with a mesh similar to a gascolator.

http://www.streetperformance.com/part/earls-performance-products/fuel-filter/226408-230206.html

http://www.streetperformance.com/ART/PRODUCTS/100625/230103_large.jpg

David-aviator
04-25-2009, 09:50 PM
...fuel pre-filter might help before your sintered bronze one?

It's a screen type, with a mesh similar to a gascolator.

http://www.streetperformance.com/part/earls-performance-products/fuel-filter/226408-230206.html

http://www.streetperformance.com/ART/PRODUCTS/100625/230103_large.jpg

I am using an Earl's screen filter before the electric pump, so far so good. I also have the AFP filter in the pump by-pass line which gets used when the electric pump is off, also so far so good.

Seems like a paper filter might be asking for trouble. Don at AFP says in the book don't do it. I nearly crashed a C150 once when a paper intake filter got wet....water may be reason paper is a no-no in the fuel system.

scsmith
04-25-2009, 10:00 PM
I would propose that you test a paper filter that has been exposed to water prior to any exposure to fuel, and then, test a filter that has been kept wet with fuel, then exposed to water.

My thinking is that if the paper element is wet with fuel, the water can't get to the paper and 'seal' it.

I remember these special funnels for filling camp stoves and lanterns. they had a brass screen in them, and if the screen was wet with water, fuel would not go through the screen. If you dried all the water out of it, then fuel would go through.

Operationally, I'm not sure if it is sufficient to be sure that the tank is never allowed to run out of fuel so the filter always stays wet with fuel? What do others think about this?

RVAddict
04-25-2009, 10:31 PM
I nearly crashed a C150 once when a paper intake filter got wet....water may be reason paper is a no-no in the fuel system.

Are you talking about the air filter on the front of the cowling? If so, why would it have a paper filter? Was the carb heat broken?

Thanks,
Josh

asav8tor
04-25-2009, 10:55 PM
This is the reason I am against running a tank dry. I want to have an option to switch tanks, to a tank with fuel, if fuel from one tank stops feeding for any number of reasons.

I think your worm is a first.... but perhaps not the last of such type events.

frankh
04-26-2009, 12:17 PM
It may not be the last worm..Certainly that is the fear.

I suspect that it is probably an extremely rare occuance and I can't see how it would happen with standard screened pickups, but with the flop tubes it certainly can.

A bit of a dilema..

Frank

frankh
04-26-2009, 12:22 PM
I did find a strainer that would fit in place of my filter with a 120 mesh screen..Ok so what does 120 mesh mean and is it fine enough to protect the rollervane pump??

Frank

frankh
04-26-2009, 10:04 PM
The filters can be installed either way..I flipped them round so the depression can catch the worm..Before it was the fact there was no room between the bottom of the element and the housing that allowed the inlet to plug.

Now I have over an inch between where the housing starts and the bottom of the filter screen. Should be ample to catch a worm.

I will look for a bigger filter housing before the next annual.

Thanks for your thoughts all.

Frank

Finley Atherton
04-27-2009, 02:42 AM
Hi Guys,


I remember I had changed to this sintered bronze in line filter at the same time I started using an E10 (ethanol blend) auto fuel.

Frank

Anyone know if there is any definitive information on the compatibility of proseal and ethanol?

Frank, Does your worm look healthy? Is it possible that the ethanol may have weakened/attacked/softened the proseal and caused the worm to come adrift?

Fin
9A

David-aviator
04-27-2009, 08:31 AM
I did find a strainer that would fit in place of my filter with a 120 mesh screen..Ok so what does 120 mesh mean and is it fine enough to protect the rollervane pump??

Frank

The 120 mesh probably means 120 microns. This should be OK. AFP recommends a 125 micron filter which is slightly more course.

The sintered bronze filters are generally very fine, the Earl's unit is just 35 microns vrs 85 microns with the stainless screen. Perhaps if you went with a larger micron filter, like the 120 you mentioned, a junk of proseal would not cause it to close completely.

chaskuss
04-27-2009, 09:31 AM
I did find a strainer that would fit in place of my filter with a 120 mesh screen..Ok so what does 120 mesh mean and is it fine enough to protect the rollervane pump??

Frank

Frank,
David is correct. The 120 means that the screen is sized to block anything larger than 120 microns. 1 micron is one thousandth of a milimeter or 25 microns = .001". Most modern auto fuel filters filter down to 25 microns. See

http://en.wikipedia.org/wiki/Micrometre

The fuel injection fuel filters sold by both Vans and AFP are made by Flow Ezy. They use a single model 6 ILA filter. I am using two filters, one in each wing root. I have selected Flow Ezy's slightly smaller model 4 ILA. These filters can be ordered with stainless steel screens rated from 238 microns down to 25 microns. RV9A builder, Chris Heitman's company, Pegasus Auto Racing Parts, sells the 4 ILA filters. See

http://www.flowezyfilters.com/image_assets/technicalinfo/HighPressureInlineFilterTechInfo.PDF

http://www.flowezyfilters.com/drawings/in-line%20filters/6IL%20series.pdf

http://www.flowezyfilters.com/drawings/motorsport%20filters/11697-09%204ILA%20series.pdf

http://www.pegasusautoracing.com/productdetails.asp?RecID=3469

Make sure you get the filter with Viton rather than Buna N O-rings. Buna N sometimes shrinks when used with unleaded gasoline.

I'm going from memory here, but I believe that Bendix called for filtration down to about 68 microns for their fuel injection systems.

Charlie Kuss
PS I'm not saying anyone is going to die from sealing their fuel tank access covers with ProSeal. However, the certified manufacturers don't do this. The real issue with fuel leakage at the access covers of RVs, is due to leakage of fuel between the retaining screws and the common K1000 style nut plates Vans supplies us with. I went with the NAS 1473-A08 nut plates that are used in the certified world. Other builders have chosen to stop this leakage using #8 pan head screws with Viton or Flourosilicone O-rings under the heads of the screws. Either method prevents fuel leakage from the access cover, without resorting to applying sealants to or in place of, the stock cork gaskets.
Frank, next time you remove those covers, I would suggest using the cork seal and the screws with O-ring seals. Don't use ProSeal.

https://i606.photobucket.com/albums/tt148/chaskuss/RV-8A/Left%20inner%20fuel%20tank%20rib%20with%20NAS1473% 20nutplates_zps3pbzfs7r.jpg (https://s606.photobucket.com/user/chaskuss/media/RV-8A/Left%20inner%20fuel%20tank%20rib%20with%20NAS1473% 20nutplates_zps3pbzfs7r.jpg.html)

Wicks carries the NAS1473-A08 nut plates. For those of you who have already built your fuel tanks, McMaster-Carr carries the #8 pan head screws with the O-rings on the under side of the head. These screws have a groove machined on the under side of the head, to hold the O-ring. Do a search on the subject. It's been discussed here on the list, several times in the past.

http://www.wicksaircraft.com/catalog/product_detail.php/pid=6653~subid=10146/index.html

frankh
04-27-2009, 09:35 AM
The 120 mesh probably means 120 microns. This should be OK. AFP recommends a 125 micron filter which is slightly more course.

The sintered bronze filters are generally very fine, the Earl's unit is just 35 microns vrs 85 microns with the stainless screen. Perhaps if you went with a larger micron filter, like the 120 you mentioned, a junk of proseal would not cause it to close completely.

Yes my sintered bronze filters are 40 microns and I don't like the pressure drop they cause (measured by blowing through them..Highly innaccurate). I will look for a more free flowing unit at the next annual.

The screen did not actually plug..the worm was about 5" long and 1/6th in width..it actually filled the space between the screen and the bottom of the fiter housing..sort of plugged the inlet pipe if you see what I mean.

I don't think the size of the mesh would have made any difference.

Flipping the filter round gives more "worm" space but a little less filter area.

It will do for now and I'll probably pull the filters at eeach oil change till I find a better solution.

frankh
04-27-2009, 09:41 AM
Anyone know if there is any definitive information on the compatibility of proseal and ethanol?

Frank, Does your worm look healthy? Is it possible that the ethanol may have weakened/attacked/softened the proseal and caused the worm to come adrift?

Fin
9A

Good question..Everything I read suggested that proseal withstood ethanol. The worm looked healthy in the that worm was like you would expect a strip of proseal to look like...I,e soft and rubbery.

I honestly thhink its where I perhaps over-applied it when putting on the cover as it had that "squeezed out between two flat plates" look to its cross section.

Frank

frankh
04-27-2009, 09:48 AM
Frank,
Make sure you get the filter with Viton rather than Buna N O-rings. Buna N sometimes shrinks when used with unleaded gasoline.

I'm going from memory here, but I believe that Bendix called for filtration down to about 68 microns for their fuel injection systems.

Charlie Kuss

Thanks Charlie..I think I might be able to get one of the smaller filters in there..Definately a good place to start some research.

I am surprised they come with Viton seals as i thought that Viton wasn't that great with ethanol and we need flourosilicone seals?..Probably not that hard to change but I can't believe they would sell a filter that is not ethanol compatible.

Will have to get my compatibility chart out.

chaskuss
04-27-2009, 10:48 AM
Thanks Charlie..I think I might be able to get one of the smaller filters in there..Definitely a good place to start some research.

I am surprised they come with Viton seals as i thought that Viton wasn't that great with ethanol and we need flourosilicone seals?..Probably not that hard to change but I can't believe they would sell a filter that is not ethanol compatible.

Will have to get my compatibility chart out.

Frank,
My understanding is that Flourosilicone resists ethanol better than Viton. Be aware that there are two flavors of Viton available. Both Viton and Flourosilicone resist unleaded fuel better than the older Buna N (aka Nitrile) O-rings. You might want to call Marco Rubber & Plastics to discuss that. See

http://www.marcorubber.com/material_chart.htm

Where did you get your compatibility chart?

I chose the 4 ILA to allow easier mounting in the wing roots. Pressure drop across a fine mesh screen will not have a great effect on fuel flow, providing you have a large enough surface area to the filter element. That is one of the advantages of larger filters over small filters.
Charlie

Lars
04-27-2009, 12:39 PM
(snip)

The real issue with fuel leakage at the access covers of RVs, is due to leakage of fuel between the retaining screws and the common K1000 style nut plates Vans supplies us with. I went with the NAS 1473-A08 nut plates that are used in the certified world. Other builders have chosen to stop this leakage using #8 pan head screws with Viton or Flourosilicone O-rings under the heads of the screws. Either method prevents fuel leakage from the access cover, without resorting to applying sealants to or in place of, the stock cork gaskets.
Frank, next time you remove those covers, I would suggest using the cork seal and the screws with O-ring seals. Don't use ProSeal.

Wicks carries the NAS1473-A08 nut plates. For those of you who have already built your fuel tanks, McMaster-Carr carries the #8 pan head screws with the O-rings on the under side of the head. These screws have a groove machined on the under side of the head, to hold the O-ring. Do a search on the subject. It's been discussed here on the list, several times in the past.

http://www.wicksaircraft.com/catalog/product_detail.php/pid=6653~subid=10146/index.html

I learn something here all the time. I'm well familiar with the o-ring'd screws that McMaster-Carr sells, but I'd never heard of the NAS1473-A08 nut plates. Thank you for posting this!

chaskuss
04-27-2009, 01:08 PM
For those wanting info on the fuel tank access screws with O-rings, I found the post below. The post mentions using Viton O-rings (this was before the advent of ethanol in widespread use in auto fuel). If you plan on using ethanol laced auto fuel, best to ask for Flourosilicone O-rings. See

http://www.vansairforce.com/community/showpost.php?p=83892&postcount=9

Charlie

frankh
04-27-2009, 01:28 PM
Thanks Charlie,

I was looking at the the pegasus site and saw a canton fuel filter that is square and uses a bottom inlet and a side outlet. It looks a little large for my application but the fittings would be in the right place to use something like this.

Then I thought, well there is no reason not to mimick this and reverse the flow on one of the inline screen jobs so the flow goes into the middle of the screen (to catch any future worms) and then I could weld a 1/4" alu fitting on the side of the body of the cartridge filter...this would reduce the overall length and I bet I could get something like that in with my wingroot pump.

About the only issue i can see is that there would be a slug of air at the top of the filter..Nothing that 30 seconds of inverted flying won't take care of..:)

And Lars your right..There are some very smart people around here.

Frank..Probably going back to cork gaskets with Oringed screws at next annual.

chaskuss
04-27-2009, 02:16 PM
Thanks Charlie,

snipped
Then I thought, well there is no reason not to mimic this and reverse the flow on one of the inline screen jobs so the flow goes into the middle of the screen (to catch any future worms) and then I could weld a 1/4" alu fitting on the side of the body of the cartridge filter...this would reduce the overall length and I bet I could get something like that in with my wing root pump.
snipped
Frank..Probably going back to cork gaskets with O-ringed screws at next annual.

Frank
The 4 ILA filters I got from Pegasus come with female 3/8" NPT on the end cap and housing. I used an AN816-6-6D from Aircraft Spruce. See

http://www.aircraftspruce.com/catalog/hapages/an816.php

Pegasus #3250-06-06 is the same thing.

You want to use 90 degree fittings, so Aircraft Spruce AN822-6-6D might work for you. If the fitting sticks out to far, just try running a 3/8 NPT tap a bit farther into the filter. This would allow you to screw the fittings farther into the housing and end cap of the filter.
Flow Ezy makes the 4 ILA with either female 1/4" NPT, 3/8" NPT or 1/2" NPT
Charlie Kuss
PS Using 90 degree fittings should be avoided if you plan on using auto fuel [E10] as they tend to cause fuel supply issues [vapor lock] when used upstream from the electric fuel pump. Better to use straight or 45 degree fittings and finish the bends with the aluminum tubing.

erich weaver
04-27-2009, 03:47 PM
Im curious - what feature(s) are unique to the NAS 1473-A08 nut plates that prevent leakage?

erich

Finley Atherton
04-27-2009, 03:54 PM
Good question..Everything I read suggested that proseal withstood ethanol. The worm looked healthy in the that worm was like you would expect a strip of proseal to look like...I,e soft and rubbery.

I honestly thhink its where I perhaps over-applied it when putting on the cover as it had that "squeezed out between two flat plates" look to its cross section.

Frank

Frank

Another thought on why the worm decided to go exploring. I have not seen the RV flop tube arrangement but is it possible that the flop tube could rub against the cover-plate area and perhaps have set the worm free?

Fin
9A

chaskuss
04-27-2009, 04:10 PM
Im curious - what feature(s) are unique to the NAS 1473-A08 nut plates that prevent leakage?

erich

Erich,
Perhaps if you followed the link I provided earlier to these items at Wicks, it would be apparent. The NAS1473-A08 nut plates offer a "blind" hole to the mounting screw. They also have an O-ring at the bottom to seal them against the doubler they mount on. You will also notice in the photo of my inner fuel tank rib, I have coated the nut plates with ProSeal. I did this on the advice of my RV guru, Jody Edwards. Jody told me that all the certified aircraft he had ever worked on, used these special nut plates inside the fuel tanks. He said that they were always coated on the exterior with ProSeal, as added insurance.
Standard nut plates, like the K1000 series, offer a "through" hole for the screw. This allows the fuel to slowly seep between the threads of the nut plate and the threads of the screws retaining the access cover. The fuel leaks past the holes in the cork gasket (provided for the screws to go through), and the fuel comes out from under the heads of the screws. Most people ASSume that the cork gasket is leaking - NOT!
The NAS1473-A08 nut plates are shaped like an acorn. There is no open back side to them for the fuel to enter into. I hope this explanation clears things up for you.
Charlie Kuss

chaskuss
04-27-2009, 04:19 PM
Frank

Another thought on why the worm decided to go exploring. I have not seen the RV flop tube arrangement but is it possible that the flop tube could rub against the cover-plate area and perhaps have set the worm free?

Fin
9A

Fin,
If the flop tube is built per Vans plans, the flop tube can not come near the sealing surface. You have to build two "anti-hang up" guides, to prevent the flop tube from getting stuck on either the inboard or second fuel tank rib. The intent is to keep the flop tube on the bottom of the fuel tank (during normal, level flight) so that you don't run out of fuel prematurely, due to the tube being caught part way up on a rib. Remember, the end of that flop tube is your fuel pick up point.
A secondary function of these guides, prevents the flop tube from contacting the access cover. I didn't like the way Van designed the guide protecting the inner rib, as it blocks easy access to the tank's interior. The guide is one piece and mounts vertically from 12 o'clock to 6 o'clock position over the access hole.
RV8 builder Steve Dixon came up with a two piece guide, which does not block access to the inner bay of the tank. I took Steve's idea and modified it a bit. The NAS 1473 nut plates are taller than the standard K1000 nut plates.
Charlie Kuss

erich weaver
04-27-2009, 04:58 PM
Erich,
Perhaps if you followed the link I provided earlier to these items at Wicks, it would be apparent.

Ouch! My bad - I googled the part number and checked a few of the listings but they had no description or picture. Should have done the obvious - the picture says it all.

Interesting info - even the guys at Vans will tell you to toss the cork gasket they just sold you and use proseal to avoid leaks. This is the first I have heard otherwise. Who wants to use proseal if you dont have to?

erich

Mel
04-27-2009, 05:09 PM
Interesting info - even the guys at Vans will tell you to toss the cork gasket they just sold you and use proseal to avoid leaks. This is the first I have heard otherwise. Who wants to use proseal if you dont have to?

I have removed MANY MANY cork gaskets that were totally saturated with fuel after a few years. I have NEVER seen a plate put on with pro-seal that leaked. I have heard of ONE "worm" (this one).

frankh
04-27-2009, 08:07 PM
This was the only worm in existance!..It is now on my hangar floor..:)

Well I just orderd the Flow ezy 4ila filter for both sides..it will be a squeeze getting them in there but there is just enough room.

I intend to reverse the flow direction in case another worm decides to come up for air..Should'nt be an issue...Normally filters are supported in the direction of flow so that if they become completely plugged they won't collaps.

I think it would be highly unlikely to ever get that far on an airplane that has its filters pulled once a year.

Thanks all

Frank

frankh
04-28-2009, 09:35 AM
What was the pressure drop through the 4ILA filter (with a 25 micron screen) by blowing through it..Noticable ot not?

Filters on order.

Thanks

Frank

chaskuss
04-28-2009, 07:29 PM
What was the pressure drop through the 4ILA filter (with a 25 micron screen) by blowing through it..Noticable ot not?

Filters on order.

Thanks

Frank

Frank
To be honest, I don't think I've ever blown into them. If you are pumping pressure through them, it's not really an issue. For me, (I still have a mechanical pump) the issue would be pressure drop with only the mechanical pump running. The filter is under suction with only the mechanical pump going.
If I ever run into a vapor lock situation (having to turn on the electric pump during cruise), I can always install a less restrictive screen. You could also order your filters with either 40 or 74 micron elements. The 74 micron unit is close to the 68 microns that Bendix recommended.
Charlie

frankh
04-29-2009, 12:28 AM
You mean your not protecting the electric boost pump with the filter??

Oh wait a minute..are you carburetted?..I.e using the Facet cube pump..they are very accepting of all kinds of dirt..the rollervane pumps have to be protected however.

Frank

chaskuss
05-05-2009, 05:06 PM
What was the pressure drop through the 4ILA filter (with a 25 micron screen) by blowing through it..Noticeable or not?

Filters on order.

Thanks

Frank

Frank,
I disassembled one of my 4 ILA Flow Ezy fuel filters (with 25 micron screen) Using your "blow through it" method, I felt no restriction to flow.

https://i606.photobucket.com/albums/tt148/chaskuss/RV-8A/Fuselage/Flow%20Ezy%204%20ILA%20Fuel%20Filter%20Disassemble d%203_zpslj5gev32.jpg (https://s606.photobucket.com/user/chaskuss/media/RV-8A/Fuselage/Flow%20Ezy%204%20ILA%20Fuel%20Filter%20Disassemble d%203_zpslj5gev32.jpg.html)

I hope this helps

Charlie

frankh
05-05-2009, 09:33 PM
yes mine arrived yesterday and I found the same thing.

Not sure when I'm going to have time to install them..I have decided to reverse the flow...should another worm appear it will drop into the middle of the filter with no problem..just a case of blowing any crud into the middle of the scree with an air hose.

If I can't fit them in lengthwise I may still weld a fitting to the outside and shorten them while Im at it (i,e cut the end off and weld a flat plate over it)

We'll see..I flipped my little filters round for the time being and may run them till the next annual..I don't have time to be messing with airplanes much as I'm doing some heavy studying till October.

Cheers

Frank