What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

ALERT! - Fuel hose obstruction!

BSwayze

Well Known Member
So... I'm working on my firewall forward tasks, and I'm at the point where it's finally time to install the fuel hoses to the engine. So the first one is the short foot-long hose that goes from the firewall fuel outlet to the engine-driven fuel pump. So I grab the hose that's been sitting on my shelf for several years now. I bought it new from Vans, and it's still shiny, clean, and brand new. Perfect.

Just before threading it on to the fittings for a trial fit, almost as a casual afterthought, I lifted it up and stretched it out straight to look through it. I could barely see a bit of light coming through it. Hmmmm... seems to me there should be more light coming through. Maybe I don't have it straight enough. So I try it again. Same thing. I wasn't sure if this was really unusual or not, having never done it before. I shrugged and reached in again behind the engine to install it. It had to be okay, it's still brand new. Then, I thought, maybe it wouldn't hurt to run a long pin or something down through it, just to make sure.

So I grabbed one of my cowl hinge pins and ran it through the hose. WHOA!!! It hit something inside, then punched through it, and all this hardened dirty debris came out!

Here's a picture of my nice new hose, and the mess that came out of it:

IMG_0872(medium).jpg


Here's a closeup of the debris:

IMG_0872(cropped).jpg


WHOA again!!

After poking the pin through and getting all of this out, I held it up again and looked through it. Wow! What a difference! I could clearly see right through it. To make sure it was truly clean, I dropped a string through and pulled a fuel-soaked small rag through it a couple of times to make sure I got it all out.

In retrospect, here are some thoughts, and some lessons learned.

Obviously, during all that time it sat on my shelf, some bug or insect had crawled in there and made this mess.I would have never guessed because my shop was always clean and immaculate. I never saw bugs or insects in there. But you know what? That doesn't matter. It happened anyway. It may have even come to me that way. Who knows. I never looked through it before.

This really shook me up, the more I thought about it. This is all downstream of the fuel filter! Had I not looked, I can only imagine how this dirty mess would have gone through the hose into my fuel pump, and the red cube fuel transducer, then right into my fuel injection system. I can see how easily it could have messed up any of those components, or clogged a fuel injection nozzle. Or maybe all of them.

I shudder to think of how close I came to installing this hose, without looking through it first. It was almost like an afterthought or a casual thing, that I just happened to take a look. I could have so easily not done it. After all, I bought it brand new and it still looks like it did the day I brought it home. DON'T be fooled by the shiny new-looking external appearance of parts like this! Danger may lurk inside.

So I wanted to share my experience, with the hope that it may help someone else. Check those fuel hoses before installing them! I don't care if they're right out of the box.
 
Dang! glad you found this. all my fuel lines and connection received JIC cap and plugs after verifying all clean and clear during the build.
 
clogged fuel line

A couple years ago a builder asked me to close & pressure test his tanks that had sat around for a few years. One tank had a flop tube in it & just before I sealed the access plate on the tank, I thought that I should blow thru it to insure it was clear of sealant. It was obstructed, so I tried to suck on it. What a MISTAKE that was! I got a mouth full of bug debris & stuff! Much hacking & a can of beer (medicinal mouth wash) later, I pulled the tube out of the tank & found half the length caked in this stuff.
I replaced the hose with new as I wasn't satisfied I was able to totally clean all the bug stuff out.
Interestingly the other tank with a standard pick-up was clean. Bugs must like that rubber material.
 
Maybe I am the only homebuilder that does it, but I have an assortment of these caps in my shop and any fitting that is not connected has one on it.

Not the only one. I kept all tubes closed during construction to prevent this exact malady. Keeping a good selection of AN tube caps is a good thing.
 
Keeping hoses sealed until installation is great and I do it , but it is still no excuse not to "flush/purge" immediately prior to installation.
 
I spend a lot of time on my daily commute thinking about things like this, I haven't done the fuel lines yet but I have read many places that fuel systems are the biggest problem in the experimental world. I'm assuming flushing is good practice as Mel mentioned but what do you flush with? Also, thanks for posting this Bruce, points out another reason to treat the fuel system like it is made of gold.
 
Maybe I am the only homebuilder that does it, but I have an assortment of these caps in my shop and any fitting that is not connected has one on it.

You're not the only one :)

ETA: to the OP...you mentioned poking a hinge pin into the tube to break up the obstruction. I'm not sure but that I wouldn't just toss that hose now...I don't know what the effect of scratching the inside of the tube with something sharp (like the end of a hinge pin) might be.

That might be overly cautious, but unless someone can chime in here and give some advice on how to inspect it, or that it's okay and can tolerate scratches, I'd err on the side of being extra careful with my fuel system.
 
Last edited:
You're not the only one :)

ETA: to the OP...you mentioned poking a hinge pin into the tube to break up the obstruction. I'm not sure but that I wouldn't just toss that hose now...I don't know what the effect of scratching the inside of the tube with something sharp (like the end of a hinge pin) might be.

That might be overly cautious, but unless someone can chime in here and give some advice on how to inspect it, or that it's okay and can tolerate scratches, I'd err on the side of being extra careful with my fuel system.

I sort of had the same thought, although I have no data to say whether "scratching" the teflon liner may be a problem. Perhaps Tom From TS Flightlines can weigh in?
 
I'm assuming flushing is good practice as Mel mentioned but what do you flush with?

Fuel?

It's a solvent, and it's guaranteed to not damage the fuel line.

The suggestion of dragging a fuel-soaked bit of rag (ghetto pipecleaner!) through the length of the hose is a good one too.

- mark
 
Absolutely!

Keeping hoses sealed until installation is great and I do it , but it is still no excuse not to "flush/purge" immediately prior to installation.

+1 - take a piece of foam, stuff in the end and blow through, wet with wd40 , mineral spirits do it 3 times. Then install. Ear plugs work well. Open cell foam is best to collect internal debris. This is standard QC process at hydraulic assembly plants where miles of hose gets installed weekly.

Who knows where the hose has been.
 
Last edited:
ETA: to the OP...you mentioned poking a hinge pin into the tube to break up the obstruction. I'm not sure but that I wouldn't just toss that hose now...I don't know what the effect of scratching the inside of the tube with something sharp (like the end of a hinge pin) might be.

That might be overly cautious, but unless someone can chime in here and give some advice on how to inspect it, or that it's okay and can tolerate scratches, I'd err on the side of being extra careful with my fuel system.

I appreciate this very much, Joe. The hinge pin I used had been rounded on the end and polished on my wheel, to make it easier to insert into the cowl hinges. There are no sharp edges at all, so I'm not too worried about it. Thanks for the suggestion!
 
Good catch Bruce! As far as the hinge pin is concerned, its probably just fine. I'd retest the hoses, just to make sure that the liner didnt get nicked in the process. Flush the hoses, and re-cap them until ready for install. UH----same for the filter, pump, etc, anything that has been left open.
Mud daubers, dirt, RTV, loctite, anything that could possibly create a restriction.
One of our local clients had a very small piece of something that restricted a port in the flow divider. AND all of his stuff was capped off----so definitely check things.

Tom
 
Message received loud and "clear"

Guess I better go check my flop tube that has been sitting on the shelf for - well - let's just say a lot longer than I care to mention. Both ends have been wide open the whole time. This even makes me wonder about the metal fuel and vent line tubing, and other NPT fittings that have been tucked away in my plastic storage drawers along with all the rivets, etc. for a very long time. You know, the ones where I periodically find dead spiders and such in the bottom of the drawer......

I've got plenty of ear plugs laying around doing nothing, so that will change. Maybe it's time to order some caps too.

Thanks for the warning and the wake up call Bruce!
 
Caps

For those who do not want to chase down the caps, a double layer of aluminum foil wrapped around the end and secured with rubber band or wire tie works well. For the shorter hoses wrap the entire hose or put it in a zip lock bag.
The cleaning brushes for the old fashioned coffee makers are probably very hard to find these days. They make an excellent cleaning brush for the -4 and larger hoses. Dish soap and lots of hot water. Stick them in the oven at around 200 degrees to get rid of any trapped water.
 
LARGE zip plastic bags, like the 2 1/2 gallon size is great for storing things like hoses, fuel pumps, filters, selector valves, etc. that have been flight ready.

Oh and the idea of sealing the fuel hoses also pertains to the brake hoses too--pitot lines, your coiled up aluminum tubing too.

Good idea that even after you remove the cap plugs use your air compressor to blow through them, just to make sure. Because, if youre like me, you may have checked them several years ago and put caps on them. Or did you? Memory gets hazy after a while. Dont guess, check it.

Tom
 
Back
Top