Air Flow Performance electric fuel pump filter

penguin · #1 11-04-2005, 05:29 PM

I wonder if those of you who have an injected engine and use the Air Flow Performance electric fuel pump (as supplied by Van's) can answer a couple of questions?
Has anyone mounted the pump forward of the firewall? and
Has anyone ever found any debris in the filter supplied with the pump?
I am considering not fitting this filter (as it seems rather coarse and expensive), and using an Andair firewall mounted gascolator instead. That means I will either have to fit the pump after the gascolator (forward of the firewall), or fit the pump in the Van's suggested position but with no upstream filter. Any thoughts?

Pete

dan · #2 11-04-2005, 05:33 PM

My AFP pump/filter is mounted in front of the spar in my RV-7. I have found debris in the filter the 4 or 5 times I've cleaned it. While there wasn't much found in there, it's enough that I don't want that crud gumming up my $500+ pump. Given the price of the pump, I would not want to have the upstream fuel supply unfiltered. Just my 2 cents!

I don't know much about the internals of the AFP high pressure boost pump. Maybe it can tolerate some amount of gunk. I'm not in the mood to find out where that threshold is. I want my high pressure pump to last at least as long as my engine's overhaul cycle.

)_( Dan
RV-7 N714D (662 hours)
http://www.rvproject.com

penguin · #3 11-04-2005, 05:39 PM

Thanks for your input, Dan. Definitely agree that it's not worth taking a chance on whether the pump can tolerate debris or not.

Pete

DanH · #4 11-06-2005, 07:49 AM

The system needs a water trap. Install a gascolator on the firewall where you can access the drain during preflight through a 1.125" cowling hole. Installing the AFP screen filter before the electric pump is fine, but try hard to locate it in a place that is easy to access....or you won't check it on a regular basis. Better none than a filter not maintained.

BTW, the Bendix throttle body has an inlet screen, but it is lightly spring loaded. If it gets even slightly clogged it will lift off its seat and bypass a lump of garbage into the TB and spider. Don't depend on it for any gross filtering.

Dan

dan · #5 11-06-2005, 07:18 PM

Needs a water trap? Why?!

A little water to a fuel injected engine (and I'm talking about a LITTLE here) ain't so bad imho.

)_( Dan
RV-7 N714D (670 hours with no gascolator)
http://www.rvproject.com

Tandem46 · #6 11-06-2005, 08:48 PM

Pete,
I have same setup as DanC. I definitely wouldn't substitute gascolator for filter. I've cleaned mine several times and always find a little something each time. As for watertraps, I don't have a gascolator. I religiously sump the tanks via the drain before each flight. I have my doubts about how effective gascolators work. Read too many stories of engine stoppage due to water contamination on aircraft equipped with gascolators. Best thing is always sump the tanks, then you know.

Tobin

mlw450802 · #7 11-07-2005, 08:51 AM

Agreed!

The tank is an excellent water trap.

-mike

DanH · #8 11-07-2005, 05:59 PM

<<Needs a water trap? Why?!>>

Sumping the tanks rarely gets ALL the water. Steel fuel system components (like line fittings) corrode and throw rust flakes into the system. Some of those components are well downstream of any filter. The one-way valves in the engine driven fuel pump are also steel; a failed valve means replacing the pump. Water tends to collect in that pump, as well as inside the throttle body. Water in the line but not yet up to the engine pump runs downhill and collects in the system low spot. Without a gascolator, the low point will likely be your electric pump assembly....you know, the $500 one.

Corrosion damage aside, yes, an engine will swallow a little water. More than a teaspoon and less than 3 or 4 ounces is gascolator territory. Without one you may get an engine stoppage, with one you probably won't notice. A gascolator won't help if you have enough water to fill the bowl, but that is why we sump the tanks. Sumping is reduce quantity. A gascolator gets the rest.

Your airplane, your choice <g>

Dan

n250jg · #9 11-09-2005, 07:41 AM

My choice was no gascolator. No matter which end you install the extra wheel, on the ground the plane sits tail low, making the sump on the tank the lowest point of the fuel system. I thought this was reason enough, but when the 1-24 tsp range of the gascolator was mentioned I got out the calculator to see if I was still alright with the decision or if a gascolator would be justifiable.

If you religiously sump the tanks before every flight like Tobin, myself, and I?m sure thousands of other people, you would be fine even if the tanks were half full of water. Once all the water is removed via the sump, or at least enough to leave the water level below the fuel pickup, you?re only left with water in the pickup line itself. Assume a builder cut half way through the 3/8in line when making the ?screen? and there was 6in of line level enough to collect water to fill that entire cross section (ours is sloped so it would be much less than that) and what?s left is less than ? tsp.

Other than the reasoning above, I didn?t want to complicate the system and add more failure points or spend an extra $150-200 on parts that I felt weren?t needed. I?ve already got enough unnecessary junk in our plane.

Or if you?re still worried about sucking water into the engine ? don?t put water in your tanks.

To answer Pete?s original post: Our AFP filter is mounted on the first bulkhead aft of the FW and yes, you will find debris in the filter, especially in the early hours. If you do decide to go with a gascolator, you should still use a filter as well.

Good luck,

osxuser · #10 11-09-2005, 10:46 PM

Sorry, but I have to agree, there is no real drawback to having a gascolator, and it can save your life. I'd have to go for one.