markhamregular

I always start my engine after I empty my tank to burn the rest of the fuel. Two of my planes will run for only a couple of seconds and die, but one of them run for a good 4 to 5 minutes each time. I figured that maybe my clunk line in the tank is too short but if the fuel pump cannot pull the fuel, the engine would not either. I guess. Any idea? Thanks.

Gray Beard

My Feedback: (-1)

Install a longer line would be my first answer but I have one plane with the line back far enough but due to the way the plane is sitting on the ground I have to lift the front of the plane to get all the fuel out. Take a look, that could be your problem too and not just a short line.

Lnewqban

Harry,

The difference is that the pump sucks a big volume of fuel and the exhaust pushes a low volume of fuel through the pick up line and clunk.

I can also be that the clunk sucks against the back wall of the tank.
For that to happen, the line have to be too long and the clunk has to not have the transversal groove.

Check if your problematic clunk is not like this one:

http://www3.towerhobbies.com/cgi-bin...&I=LXAHE9&P=RF

markhamregular

Taking out that tank could be a lot of work. I will try to pull the plane's nose up while using the pump, because as you said I think I have a long line and the clunk is against the back wall.

Thanks for your input. So, ideally, for when I am building the next plane, the cluk should be in the middle of the tank?


BTW Newban, I like your quote, can you forward it to all the extreme right anfd left people of this country?

JohnBuckner

My Feedback: (1)

No you do not want to end up with the clunk in the middle of the tank. Ideally the the clunk type tank system should have the clunk near the bottom rear corner of the tank but not touching the rear/bottom wall which can cause an insufficient flow of fuel and can also stop the clunk from doing its job of moving from the bottom/rear wall when inverted to the top/rear wall and even the sides.

What you don,t want is the clunk stuck in the same position. Its likely the discrepancy in fuel residue left in you tanks if the airplane has tricycle gear is as simple as the tank just positioned a bit front low. Many times on many airplane just sitting there to completely empty that tank as much as possible it is of course neccessary to hold the tail down or the nose up slightly.

John

Gray Beard

My Feedback: (-1)

My clunks are about 1/8 or 3/16 from the back of the tank. When I put one together I have a bright light on my bench and I rotate the tank in front of the light and watch what the clunk is doing, it must move freely like John said or it will stick and not get into the fuel at all angles.

TedMo

Reading your post with the bright light used to see through tank just has me thinking- why don't they make these tanks clear enough to see through them? Some aren't
too bad others are impossible.