Recently purchased “newly built” Model 3. Fuel tank epoxy woes.

[KenLee777]

Here is a cautionary tale! In May this year I bought a pristine looking Kitfox model 3. It was a 1992 project with Rotax 912,that was only completed in 2018. When I purchased it, the engine had been through a thorough inspection and all new hoses, rubber etc. Airframe had been stripped and recovered. Fuel Tanks had been sloshed and sealed with “fuel resistant” epoxy. I had an AnP friend check the plane out. It was just out of Phase 1. Apparently flew very nicely. I bought this for my son to build some time and have fun. I work in China so I thought that I would also enjoy flying it when I come home every six months. The airplane was trailered home to Arizona by the AnP. Upon receiving it there began a series of problems with rough running. My son and a friend started troubleshooting. Checked all the usual suspects, carbs, ignition, air. All fuel lines from gascolator back were checked. They found that fuel flow was very poor. The fuel shutoff valve was in quite a sorry state. Have a look at the picture I’ve attached. The seller had been using 91 octane auto gas. I’m really disappointed and concerned. I don’t think that anything made it past the gascolator. Wondering if I should remove the fuel tanks and install new fuel tanks? I think yes! After reading some of the older threads on this very helpful forum, I suspect that the fuel tanks will be the source of the problem. They are the small 6 gallon tanks. This means opening up the wings. I would probably install the larger tanks 13 gallons and increase endurance. Of course this would have implications to weight and balance, but I suspect there are a few model 3s flying with 13 gallons aside? Does anyone have any advice? I’ll attach some pictures.

[bbs428]

I would flush those tanks with fresh fuel and put it thru a stainer to see how much debris is still in the tanks. If they start to run clean the I'd be tempted to put two larger style filters coming down out of the wings and monitor them/change them frequently. I didn't see any fiberglass strands in your pic like I've seen in others.
I can't comment on the model III and the larger 13 gal. tanks - no experience with it. I know the model IV wings are different and the bigger tanks were designed for that wing so,

Hope it all works out for you and your son.

[avidflyer]

I would agree with trying to wash out the tanks with fresh fuel, but I would not put fuel filters between the wing tanks and header tank. That is a gravity feed situation, and it doesn't take much to stop fuel flow when it's just gravity feed. I have had an unplanned off field landing because of this. After the header tank, the fuel pump is providing suction, and will have a much easier time getting fuel through a partially plugged filter in that location. And for that mater, the header tank is really a large gascolator, so it should stop most stuff coming through. Just my 2 cents worth, and worth every penny you paid for it! :-) JImChuk

[bbs428]

"I would not put fuel filters between the wing tanks and header tank. That is a gravity feed situation, and it doesn't take much to stop fuel flow when it's just gravity feed. I have had an unplanned off field landing because of this...."

Agreed - haven't thought of that. Makes me rethink that using a fuel pump might be a wise choice after the header tank.

[KenLee777]

Gentlemen,
Thank you for the advice. I’ll let you know what we find. Regarding filters between the wing tanks and header tank, I agree on not putting them there. I do like the idea of having an electric boost pump or back up pump after the header tank. Any thoughts on adding Marvel mystery oil into the fuel to aid in cleaning up any crud. I will burn avgas and add decalin to deal with lead. Looking forward to departing cold Shanghai in December and heading home to clean air, blue skies and getting this airplane flying safely. I sincerely appreciate the resources on this forum. Once the fuel problem is managed, I have a set of grove gear that I need to install. The airplane currently has the tubular gear with bungee. I also would like to either fit a trim tab to the elevator, or install a detent to hold the flaperon lever in place. When we did manage a brief flight, the flaperon lever would not stay put and this meant we had to maintain forward stick pressure to fly level. The current friction system to hold the flaperon lever in place is not very effective. That’s a discussion for later.

[sturdee]

I would agree with trying to wash out the tanks with fresh fuel, but I would not put fuel filters between the wing tanks and header tank. That is a gravity feed situation, and it doesn't take much to stop fuel flow when it's just gravity feed. I have had an unplanned off field landing because of this. After the header tank, the fuel pump is providing suction, and will have a much easier time getting fuel through a partially plugged filter in that location. And for that mater, the header tank is really a large gascolator, so it should stop most stuff coming through. Just my 2 cents worth, and worth every penny you paid for it! :-) JImChuk

That’s interesting I have two 13gal tanks with 5/16 pipes and 5/16 stop cocks and glass see through filters down to the aluminium header tank and never had problems with restricted flow. The taps allow me to select either side which when departing with full tanks I run off the right first to allow a space for the vapour return too go , otherwise you could over flow the right tank. After the Fuel shut off valve I have the standard gascolator before the fuel pump, no electric back up. 80hp Rotax
mike