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Fuel Line Cleaning

sglynn

sglynn

Well Known Member
Any body cleaned their fuel lines just before completion? I'm thinking there might be dust in the lines because I've working on this for 10 years and now almost done seems like I should blow out the fuel lines before running fuel thru them and thru the filter and pump. My fuel lines are all hooked up from engine thru aux pump, filter and out to the wings. Wings are not on yet.

Can I blow from the firewall back thru the aux pump and filter and out the wing connections? Or is the pump/filter a stop so that I need to clean them from there in both directions? I'm assuming air will blow thru the valve one side at a time. Right? Will blowing air thru this break something? Perhaps better question is will blowing air thru the lines do any good?
 
I've had the same thought. My solution was to get everything hooked up, then run fresh gas from the tanks all the way though the AUX pump, then take the gas that come out and put it in my lawn mower. Thats my plan, but I havent done it yet.
 
Robin8er said:
I've had the same thought. My solution was to get everything hooked up, then run fresh gas from the tanks all the way though the AUX pump, then take the gas that come out and put it in my lawn mower. Thats my plan, but I havent done it yet.
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And that can simply be part of the fuel flow test recommended by the FAA before first flight. :)
 
Robin8er said:
I've had the same thought. My solution was to get everything hooked up, then run fresh gas from the tanks all the way though the AUX pump, then take the gas that come out and put it in my lawn mower. Thats my plan, but I havent done it yet.
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Have the 100LL go through the system with a cheap see thought filter before collecting in your multiple 5 gallon cans. Use the collected fuel to repeat if needed. If you have an inline filter, don?t forget to remove, inspect and clean if needed when done.

As mentioned before, this is the time to do the fuel tank sender calibrations and fuel flow tests.

Carl
 
filter

If I run fuel thru from tank to engine will the Andair filter possible plug up if there is dust in the lines? Better to remove that for first couple of flushes I guess.
 
az_gila said:
And that can simply be part of the fuel flow test recommended by the FAA before first flight. :)
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I couldn't agree more.

As a Technical Counselor, I'm amazed at the percentage of builders that I've talked with hadn't even considered doing fuel flow tests, even though its highly recommended. Unfortunately, I've had to document that conversation more than once of the Technical Counselor form.

Be sure to test normal ground attitude, level flight attitude, and a normal climb attitude. Depending where your third wheel is located, some of these may be the same or close to each other.

These test should flush any debris out of the fuel lines. Be sure to check the screen in your fuel filter right after the tests too. If you fail the test, you'll know that you have some blockage somewhere. While there may be one out there, I've yet to see a RV that didn't exceed the fuel flow requirements.
 
rleffler said:
I couldn't agree more.

As a Technical Counselor, I'm amazed at the percentage of builders that I've talked with hadn't even considered doing fuel flow tests, even though its highly recommended. Unfortunately, I've had to document that conversation more than once of the Technical Counselor form.
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What is the best method for the fuel flow test? Disconnect the fuel line from the Injection servo and run the pump and measure gallon per minute?

If that is the correct method, what are the numbers that we are looking for an IO-390? I am sure this got to be a lot more than what the engine can burn when is all connected and at full power.
 
I believe the fuel pump should be capable of providing 150% of max fuel flow at takeoff power, std. day seal level. For my IO-360 I figured max fuel flow to be 18gph (I'm showing about 16.5 gph on t/o). My Andair pump put out 35 gph during my fuel flow tests. If you figure 0.9-1.0 gph/ per 10 hp. you will be in the neighborhood.
 
While building my plane (or later whenever removing and/or replacing a hose), just before assembling a hose into the airframe, I'd run a small wire through each tube/hose, and pull a solvent soaked swatch of cloth through. It was amazing how much crud would come out. I'd repeat this until the cloth came out clean. Then I'd blow them out and immediately assemble the hoses, and cap off any open ends which may exist. Blue masking tape from 3M works for this as it comes off without residue if one doesn't have a true cap.
 
Blow through with foam ear plugs.

AlexPeterson said:
While building my plane (or later whenever removing and/or replacing a hose), just before assembling a hose into the airframe, I'd run a small wire through each tube/hose, and pull a solvent soaked swatch of cloth through. It was amazing how much crud would come out. I'd repeat this until the cloth came out clean. Then I'd blow them out and immediately assemble the hoses, and cap off any open ends which may exist. Blue masking tape from 3M works for this as it comes off without residue if one doesn't have a true cap.
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If the tubes/hoses are not assembled, you can take a foam ear plug and stick in one end and blow it through three times. For larger hoses a similar wad of open cell foam will work. Add some solvent or wd-40 if you wish, but a mechanical wall scrub is better than just some air. This is done for miles of hydraulic hose in machinery production plants for contamination control, and is well proven to reduce warranty.

If all is assembled, then purge the system tank to servo and discard the first two quarts of fuel. i.e.a fuel test, as posted.

EDIT: Dont forget to run a wing-root-to-servo-pressure (air) test for leaks before filing with fuel. Then run a flow test at max pressure needed for the engine, measuring with your flow transducer.
 
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Before my first engine start, i pulled the fuel line at the carb and ran the boost pump to push 2 gallons through. I ran it through a filter before the gas jug and had a decent amount of junk.

Larry
 
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