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AFP inline fuel filter or gascolator?

G

gh6gh6

Member
I am wondering about the AFP inline fuel filter. Cleaning it annually without spilling and stinking up the cockpit and the lack of water seperation. I am thinking about plumming it out of the system and installing a gascolator on the firewall which solves both problems. Any thoughts?
 
I put that filter on the forward side of the firewall, but I got my kit before the "package" of spaghetti was offered. Water separation is not really an issue with FI. Water is an issue for carbs because the driving pressure differential in a carb is very low, and the higher viscosity of water as compared to fuel might be enough to stop the water from being pulled through the jet. However, in a FI system, water will be pushed right through the system.
 
I mounted an in-line (AFP) filter on the engine side of the firewall of my -4. It is a pain to access and makes a mess every time I open it to check for debris. When I built the plane, I considered a gascolator and bought the Andair unit, but elected to go with the in-line filter. I like the gascolator, but, ideally, the filter should be before the boost pump. I did not do this in my plane and regret it. I have considered using a pair of in-line filters spliced into the fuel lines that go to the selector, but can't stand the thought of grounding the plane long enough to make the change.

Good luck,

Dean Pichon
RV-4/400 hrs
Bolton, MA
 
I was talking to the tech help at Vans Friday about this. My RV-8 has an 180 hp IO-360 and does not have a filter but does have a gascolator. He says that as long as you have one or the other you're ok, but with the higher boost pump pressure in a FI application, the gascolator is an opportunity for a leak. If it doesn't leak with the boost pump on he said it's fine.

The higher pressure boost pump is apparently why Vans and Airflow Performance prefer a filter on the low pressure side of the pump. The connections and assembly are therefore exposed to only atmospheric pressure and are less likely to leak.

What others have said about water being less a problem with FI is also true. A little water will go right on through. Dirt is the bigger problem. Something has to be in the system to keep dirt from clogging something up.
 
Filters Only

I have a filter in the line from each of four tanks, no gascolator, no problem in 400 hours.

Bob Axsom
 
AFP Filter

Gascolators and/or the pic up screen are no comparison to the AFP filter. Perhaps the AFP folks who cruise this forum can chime in, but the AFP filter is extremely fine and has a huge surface area. The pic up tube is very course in comparison and most gascolator filters have very little surface area for filtering and are designed so if they plug up, they still will pass fuel with no filtering.

I disconnect the fuel hose at the Servo, hit the boost pump until the fuel in the line is expelled, you can hear the pump when it starts to go dry. You might spill a drop or two, but very little fuel spills in the cabin from my experience.

As always, my two cents.
 
JonJay said:
Gascolators and/or the pic up screen are no comparison to the AFP filter. Perhaps the AFP folks who cruise this forum can chime in, but the AFP filter is extremely fine and has a huge surface area. The pic up tube is very course in comparison and most gascolator filters have very little surface area for filtering and are designed so if they plug up, they still will pass fuel with no filtering.

I disconnect the fuel hose at the Servo, hit the boost pump until the fuel in the line is expelled, you can hear the pump when it starts to go dry. You might spill a drop or two, but very little fuel spills in the cabin from my experience.

As always, my two cents.
Click to expand...

Not all gascolators are the same! Those from Andair outperform the others and make checking/cleaning the filter easy.

Pete
 
You must put the filter on the low pressure side of the pump. The filter is as much for the pump as it is the injectors. The pump will fail MUCH sooner with no filter and will last much longer with a replacement filter element to a finer mesh. I have been around this bush more times than I care to remember.

The 25 micron ( 0.001") filter element for the Flow Ezy Model 6 ILA
filter (as supplied by AFP and Vans) is part number 8504-05. Price on Flow
Ezy's web site shows a price of ~$40. This is a direct replacement for
the stock 174 micron element. FYI Bendix mandates a filter element of no
more coarse than 74 microns. Want to do it right? Get the 25 micron filter element replacement and put the filter on the low pressure side of the pump. I know $40 seems like a lot. But it wont when your pump fails in the field.
You can find the 6 ILA filter here.

http://198.170.245.162/flowezypagehydraulicfilters.html#HIGHPRESSUREIN-LINEFILTER
FE-page_2901.jpg




To add to the information, a direct replacement fuel pump when your on the road to the AFP pump is a Carter fuel pump part number P74015. You can pick these up at your local auto parts store and should be around $120 in the field. It will get you back in the air.

Best
 
Very impressive and usefull information. Should be included and supplied by AFP and/or Vans when we buy these things. I intend to print this out and add it to my OM.
 
A little more info please...

Since my -8 does not currently have a filter, just a gascolator, I would need a filter with bracket, either:

6ILA-03-25-U for Buna seals, or
6ILA-03-25-F3-U for Viton seals

What seal material is best for av gas?

I assume I need a 3/8" NPT port? (the "03" in the code above) and would use two AN 816-6-6D aluminum flared tube and pipe thread nipples to connect the filter to the fuel line.

Does it sound right or am I missing something?
 
Is pressure drop an issue?

I'm planning to re-locate the fuel filter in my -4 and have followed this thread with interest. According to my AFP manual, the filter supplied is 125 micron. I am concerned that a 25 micron filter could generate more of a pressure drop than the pump can handle and reduce flow to the engine. Has anyone been running a 25 micron filter?

Thanks,

Dean Pichon
 
Pressure drop was my concern too...

Even though I have a carb, I installled a 74 micron prefilter after the selector to keep trash out of the pump and fuel flow sensor. I'm not sure it's a great idea to install too fine a filter in the suction line and 74 is the recommended size from what I could find out. I also have an Andair gascolator on the firewall.
 
Dean Pichon said:
I'm planning to re-locate the fuel filter in my -4 and have followed this thread with interest. According to my AFP manual, the filter supplied is 125 micron. I am concerned that a 25 micron filter could generate more of a pressure drop than the pump can handle and reduce flow to the engine. Has anyone been running a 25 micron filter?

Thanks,

Dean Pichon
Click to expand...

Yes, and on an IO-540.
 
I talked with AFP several years ago about this.

They were comfortable at the time with the Andair gascolator (which has a much finer screen) as the only filter in the system.

In my -8, I put the gascolator in the left wing root, after the fuel selector but before the boost pump. This has worked well to date and is trivial to service.
 
Last edited:
Bubblehead said:
Since my -8 does not currently have a filter, just a gascolator, I would need a filter with bracket, either:

6ILA-03-25-U for Buna seals, or
6ILA-03-25-F3-U for Viton seals

What seal material is best for av gas?

I assume I need a 3/8" NPT port? (the "03" in the code above) and would use two AN 816-6-6D aluminum flared tube and pipe thread nipples to connect the filter to the fuel line.

Does it sound right or am I missing something?
Click to expand...

Viton seals. And the rest is correct.
Sorry for not replying back sooner.
I do not recommend gascolators.
Best
 
LP side leaks?

Kahuna said:
You must put the filter on the low pressure side of the pump. The filter is as much for the pump as it is the injectors.
Click to expand...

Thanks for this post. Very good info and a bit contrary to my prior thinking. I see your point about pump protection.

I originally wanted to install one filter in each wing root for servicability, but then was concerned about leaks. I thought it might be best to have as many couplings (read potential leak paths) on the HP side of the pump. In this manner, a leak would be noticed. If you get a leak on the LP side, you will be sucking air into the system and would not likely find it the easy way.

Thoughts?

Also, can you (or anyone) comment on suitability of Viton o-rings for use with Mogas with alcohol. Not that I plan on burning such, just wanting to cover all potential emergency fuel options.

Regards,
 
Last edited:
Thanks for the added info, Kahuna.

I checked for the fuel pump you mentioned Here is a like to one place that sells it. It looks like the one from Vans.

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=CTR&MfrPartNumber=P74015

Their price is $72.99. Note that it is just the pump, not the other parts that come with it from Vans but if all you need is the pump, this might save a bunch of money.

The fuel pump system looks like it has three parts. I think the large cylinder is the pump itself. Then a smaller gold anodized part, and then a smaller still blue anodized part. Can someone fill me in on what the gold and blue parts are?
 
I thought the fuel filter was a separate unit. And which is which (gold, blue). By pressure return valve I assume that's a check valve?
 
Yes, the filter is separate.

I am not sure which item is which by color as i am not at home to check, but there is a Relief Valve and a Bypass Swing Check Valve that are part of the assembly.

As with all of Vans pre-assembled parts, they are usually a pretty good value for the money. By the time you end up with the pump, valves, tubing, mount, and other supplies, plus your time to source and fiddle, you might be into this more than you think.
 
I agree. I'm not trying to assemble a complete unit - I already have one working fine in my RV-8. I'm just trying to better understand the innards.

Here's a picture to help everyone's memory.

 
Fuel system parts

The blue part is a check valve. This keeps the high pressure fuel pump on the engine from pushing fuel back through the electric fuel pump. The gold part is a relief valve. It allow continuous flow through the pump when little on no flow is going through the firewall. The fuel just recirculates through the pump and a short amount of plumbing. The fuel filter in Van's setup is in a gold anodized cylinder nearly the size of the fuel pump. But it is not shown in your picture.

-rob
 
Boost Pump Operation

rvermeland said:
The blue part is a check valve. This keeps the high pressure fuel pump on the engine from pushing fuel back through the electric fuel pump. The gold part is a relief valve. It allow continuous flow through the pump when little on no flow is going through the firewall. The fuel just recirculates through the pump and a short amount of plumbing. The fuel filter in Van's setup is in a gold anodized cylinder nearly the size of the fuel pump. But it is not shown in your picture.

-rob
Click to expand...

If you describing the Airflow Performance pump, you need to get the correct information, which by the way, is with every pump we send to Van?s or provide with pumps that are shipped from our facility. The blue valve is the relief valve. This sets the pump out put pressure when the pump is running. Since the pump ?acts? like a positive displacement pump (it?s not really) the excess fuel that the engine is not using gets circulated back to the inlet of the pump. With out this valve the pump will generate around 125 PSI; also fuel is necessary to cool the motor so the re-circulating fuel accomplishes that. The gold valve on the assembly is a swing check valve. Its purpose is to allow free flow to the engine driven fuel pump when the boost pump is off. So when the pump is on the swing check valve closes to keep the pump output from short-circuiting back to the inlet of the pump. If you need the installation and operation manual for this pump assembly P/N 3090050 or the filter assembly P/N 1090079, contact me by email and I can send you a copy


Don
 
Don:

Do you have any comment regarding the previous recommendation (see post #11 on this thread) to change the filter element to a 25 micron screen?

thanks

erich
 
erich weaver said:
Don:

Do you have any comment regarding the previous recommendation (see post #11 on this thread) to change the filter element to a 25 micron screen?

thanks

erich
Click to expand...

I certainly don?t want to step on Kahuna?s toes, and everyone is entitled to their own opinion. We based the filtration size of the P/N 1090079 filter on flow capacity, and the partial size that would lock up the boost pump. Based on the filter area and the amount of debris that could be absorbed by this filter element and pass until it restricted the flow to a point that vapor was possible were the parameters that we used to come up with the filtration rating. Other factors were the filtration down stream in the fuel injection unit and in our case the flow divider. So when people arbitrarily install finer filters, they may get by with it if their fuel is always clean. If 25 microns is good, why not put in 5 microns to be sure. If you had unlimited filter area this would be the way to go. I don?t know what his issue was (may have been installation related that lunched the pump) but we have found that the filtration rating we designed for this filter works in 99.9% of the installations. It?s flown around the world in a Long EZ and has accumulated over thousands of hours without problems. So for what it?s worth that?s our story.

Don
 
Not stepping on my toes and Im glad you jumpped in. In my case for my rv-6 4 banger, I was burning up pumps ~250 hours. Pump would make strange noises for ~50 hours then stop working. I think I burnt up 3 pumps. Filter was part of the pump assembly right before the pump. At the recommendation of I cant remember who from the RV-List, I tried the 25 micron. It lasted 750 hours before I sold the plane.

With those limited data points, I put the 25 micron in my Super 8. It has been working fine for ~600 hours. Based on my data, if the 25 flows enough for the 6cyl lyco, then an even finer mesh would flow enough for the 4 cyl. I would say you would want the absolute finest mesh possible that still gives you the maximum flow needed and not a drop more, at some % of clogged up. Need to max flow with debris in there. Based on my limited experience over ther years cleaning fliters, that percentage would be less than 5% but thats a SWAG. Just my 2 cents.

Best,
 
I used Earl's Perfomance inline filters from each tank before the selector. They use AN6 flare fittings and are easy to change. About $25.00 a filter, ouch.
 
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