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Reusable AFP fuel filter and solvent

Kahuna

Moderatoring
Over the past 500 hours or so I have noticed a slow progressing need for the boost pump, culminating in fuel starvation and an uneventful landing on a recent cross country.

A check of the fuel line at the servo and boost pump on resulted in fuel shot across the ramp. Seemed fine. Test flight, and again fuel starvation.

A check of the fuel filter show nothing. Visually spotless. Until I tried to blow through it. Definite restriction. Cleaned filter with carb cleaner, and I could see a light yellow color in the solvent. Reassembled, and no restriction blowing through it. Problem solved. Flown another 10 hours until home with no need at all for the boost pump which is something I had not seen in years.

This is an AFP 40 micron filter. One of those 6ILA assemblies.
AO-8504-04-300x300.jpg

I checked the paperwork for cleaning instructions and "The filter element can be removed from the filter cap and cleaned in mineral spirits then blown dry with compressed air"

Hmm. "Can be"

Checked with a couple other high time experienced RV'ers, and they too had never run solvent through the filter.

With 2500 hours over 20 years on the filter, I have never done more than visual inspection, clean off any debris, and reinstalled. Never any solvent. I have no idea what had been building up in inside the element, but obviously something had. Also no indication in the docs about service life. Installed a new one.

Lesson?
1. Dont let a slow creeping issue go unresolved.
2. Clean the filter with solvent at annual.
3. After assembly, blow through the housing, it should blow quite freely.
 
Dissolve what gasoline won't.

Thanks for that information. The solvent should be more "aggressive" than mineral spirits or it may dissolve nothing.

Knowing that the spray carb cleaner works is my key takeaway.

This leaves curiosity about just what yellow substance/particles could exist in gasoline and plug this filter. Is it mogas fueled, 100LL or both?

The standard filter is 74 micron, any reason for the 40?

You say a new one was installed, was the carb cleaning solvent not satisfactory, or just precaution (nothing wrong with that).

Is there slosh or some regular use of ez-turn that might accumulate? ez-turn is a liquid polymer, polypropylene I think. Maybe it could shed and plate the filter. It could only come from caps, or limited sources to hit this filter.

Yes the final answer - is to clean and replace the darn filter !!
 
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This leaves curiosity about just what yellow substance/particles could exist in gasoline and plug this filter. Is it mogas fueled, 100LL or both?

I have never run mogas in it.
Coarse screen at the servo inlet was clean.
 
Back in the automotive days, I used to use alot of carb/injection cleaner. WE found that auto fuels, would leave some gummy residue, and color like Kahuna mentioned. Even soaking a carb in the those submersible cleaners didnt clean the residue like carb cleaner. Extra care to NOT get it in cuts, eyes etc!
Been doing it that way for +45 years. Works very well on stainless screens.

Tom
 
Is the just a screen or is there any other media. Can't tell from the picuture.

The "Cleaning" procedure from the OEM most certainly had to do with flushing particulate away. Your situation is different. BillL is probably correct regarding some substance is being suspended and depositing on the element parent material. Filters are areas of relatively low fluid velocities so that doesn't help. I'd bet slosh if no corresponding fuel system maintenance has been done in this timeframe.

Also, double check the required filter beta rating. Finer (higher number) isn't necessarily better. It can be acceptable but typically you'd want to increase filter media surface area; bigger canister.
 
Anyone know what the filter size is at the fuel station pump? I guess there must be a standard, and I'm guessing it's bigger than 40 micron.

We had a presentation from a guy from Total at our chapter meeting a couple of years ago, and it kind of scared the çrap out of me. He had some horror stories that he used to emphasize how they (Total) take extra precautions to not have problems with their fuel.
 
Is the just a screen or is there any other media. Can't tell from the picture.

There is multiple media in the filter. An outer screen mesh, and something else inside. Some kind of fine woven mesh, hard to discern.
 
The standard filter is 74 micron, any reason for the 40?

You say a new one was installed, was the carb cleaning solvent not satisfactory, or just precaution (nothing wrong with that).

Is there slosh or some regular use of ez-turn that might accumulate? ez-turn is a liquid polymer, polypropylene I think. Maybe it could shed and plate the filter. It could only come from caps, or limited sources to hit this filter.

Yes the final answer - is to clean and replace the darn filter !!

Years ago, I had a 6a that i put ~2k hours on. I had problems with the pumps every 500 hours getting really noisy. One failed. I believe it was Charlie Kuss that was knowledgeable on them and suggested a finer filter. So I went to 40. That stopped the pumps getting eaten. I ran the pump mostly always due to the flying environment it was in mostly. Low level with other planes.

No, no slosh in this plane. Yes EZ lube used as rarely as maintenance seemed necessary. Nothing I would deem as excessive. But of coarse that lube is going somewhere.

Yes the carb cleaning solvent did work. In fact very well as I mentioned. I replaced the filter just cause I didnt trust it.
 
"Cleaned filter with carb cleaner, and I could see a light yellow color in the solvent. Reassembled, and no restriction blowing through it. Problem solved."

Kahuna, wondering if you submerged the entire filter with the o-ring on it. If so the yellow discharge may have come from the o-ring. Carb cleaner is a very aggressive cleaner and can attack rubber compounds.
 
There is multiple media in the filter. An outer screen mesh, and something else inside. Some kind of fine woven mesh, hard to discern.

You'd be wise to replace it, IMO. None of us know the exact fouling agent; however, the Vegas odds are not in your favor regarding returning the element to a condition of any long term serviceability. Whatever it is, it's already displayed an affinity for the media (probably the fibrous one) which probably can't be entirely removed with a reasonable solvent flush. Subsequent accumulations will occur quicker and without real predictability.

Replace it with an element of proper beta IAW the fuel system OEM's recommendation. If you can get a properly rated one with a single stainless media, I would. You ultimately need to determine the source/identity of the fouling agent. Sounds like you may have already dodged a couple of bullets. Keep us informed.
 
Kahuna, wondering if you submerged the entire filter with the o-ring on it. If so the yellow discharge may have come from the o-ring. Carb cleaner is a very aggressive cleaner and can attack rubber compounds.

No not submerged, spray carb cleaner. I could see the light yellow tint initially during spray flushing. Then clear.

Just to be clear, Im not recommending carb cleaner. It is just what was available at a remote field doing a repair.
 
This is an AFP 40 micron filter. One of those 6ILA assemblies.
AO-8504-04-300x300.jpg

Time out.

Yes, AFP sells a 40 micron filter, and a 74, but the recommended inline filter prior to the boost pump is a 125 micron unit. The servo inlet has a small 75 micron filter, as does the flow divider. It's right there in the manual.

AFP sells stuff for all kinds of systems. The fact that they sell it doesn't make it right for every application.

The 40 micron has a place. For example, a builder might install a 40 micron filter in the line between the engine driven pump and a Silver Hawk fuel control, as Precision specifies fine filtration just prior to their unit. Note that in this application the 40 is a push-through filter, downstream of the pumps.
 
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Back in the automotive days, I used to use alot of carb/injection cleaner. WE found that auto fuels, would leave some gummy residue, and color like Kahuna mentioned. Even soaking a carb in the those submersible cleaners didnt clean the residue like carb cleaner. Extra care to NOT get it in cuts, eyes etc!
Been doing it that way for +45 years. Works very well on stainless screens.

Tom

+1

We called it varnish and is very common in lawnmower and other engines that are not used much. It usually is a darker yellow to tan color. I assume it is not the gas, but one of the additives. Unsure if those same additives are used in 100LL.

This stuff if the reason that a lawnmower needs it's carb torn down and cleaned after sitting a few winters. They are small carbs with tiny jet sizes. In my experience, only carb cleaner or equally strong solvent will remove it without mechanical support.
 
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I cut the filter. There is no mesh inside. The only filter is the outside screen. The rest of the filter is designed to maintain the outside screen structure. Couple of pics attached.
 

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Thanks!

I cut the filter. There is no mesh inside. The only filter is the outside screen. The rest of the filter is designed to maintain the outside screen structure. Couple of pics attached.

Thanks for doing that!! As I was reading though this string and there was mention of a secondary media, bells were going off that Carb Cleaner can be so aggressive so as to dissolve polymer binders in a media and really cause problem and/or result in much poorer than spec filtration. Glad to see this unit is all metal.

Carry on!
 
Dont use a paper or sintered metal filter. Stainless filters are the way to go. Easily serviced, rugged and reliable, and most cleaning solvents wont hurt them.

Larry ===varnish was the word I was looking for. Thanks!! I dont know what chemicals are in fuel and I do know that they change. Some do attack rubber parts, like O'rings. So yes, Mark--remove all rubber, neoprene, viton etc parts before cleaning---you never know what may not be compatible. ( Ever put an autmotive master cylinder diaphram in varsol? LOL----watch it expand!)

Tom
 
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