shawntoast

I have an os .46 on a Nexstar select and when I crank it, it fires right up, but it acts like its sucking air through the fuel lines out of the tank, (well you can see it coming through the lines) and it of course stutters and tries to die. I have replaced all the fuel lines and landed it dead stick twice since. It will run sometimes but the more juice you add, the more air you also get. any suggestions?

bassmanh

My Feedback: (5)

shawn,

a couple simple things to check first, are the fuel lines connected right ? clunck line going to the carb vent line to exhaust ? clunck stuck in the front of the tank ?

make sure all lines are tight with no leaks. is the fuel tank rapped in foam rubber so the fuel doesnt foam and get airbubbles in the lines ?




bassman

draftman1

welcome. first, which engine is it, AX, FX, LA or other? second has this plane had a hard hit to the ground? sometimes an impact will make the tnk clunk bend and get kinked. check all bolts on the back of the engine. the LA series backplate is plastic and it does leak air. clean it up good and reseal back plate with some RTV silicone on the backplate. check the carb for leaks. the needle valve can leak also, take out the needle valve, put a short piece, about 3/16" long, fuel hose on the needle valve and screw it back in. after youdo all that, then if your a club member, have your best engine tuner get the mixture right.

shawntoast

Thanks Bassman,
I've checked it all once and replaced all the lines, I had just put the tank back in and pulled it towards the rear a little so I wouldn't kink the lines. I also had the cap off the tank, and made sure the klunk was free............I guess I'll go take it all apart again the air has to be getting in somewhere huh.....
Thank alot for the suggestions though. by the way, I've just joined so maybe I'll catch up w/ ya later. shawn

shawntoast

it is the FX

bassmanh

My Feedback: (5)

shawn,

also check the O rings for carb and make sure the carb is seated well and tight. and as suggested check all the bolts to make sure they are tight.

along with the remote needle valve be sure the nut is tight there also.

now if its not any of those you might just need to get it tuned right.



bassman

shawntoast

I appreciate all the replies, I don't think it is at the carb or the back plate on the engine. You can actualy see the bubbles coming from the tank through the remote needle valve and to the carb. can anything you guys mentioned cause this? I'm not an expert (or I wouldn't be flying a nexstar LOL) I don't see how it could be the seat under the carb. The particular tank I'm using came with the plane and the hole in the firewall that the fuel lines come through matches the neck on the fuel tank, (it only fits one way) It is a 3 tube setup and the klunk is on one and the other two have metal curved lines that curve to the sides of the tank.( top and bottom) it shouldn't matter which one goes to the muffler for pressure, and which one gets plugged during flight for fuel fill should it? or does it? I have the tank back out and plan to pick up another gallon of fuel and run it on a test stand later this week. Unfortunately, I'm one of the redheaded step children who refused to join a club (due to bad experience when I was younger with a particular club) and have learned what little I know by reading books, and well Surfing the internet! so Iguess what I'm trying to say is that my help resources are limited. I appreciate it guys........ shawn

bassmanh

My Feedback: (5)

shawn,

first thing is see if you can find someone that can help you tune your engine. i know you dont belong to a club but you cant let 1 bad experience keep you from meeting a good group of people who can and will help you fly. now with that said see the below

yes it does matter what line goes to the muffler if you have it hooked up to the in tank line that goes to the bottom, that is the fill line and if you have it hooked to the muffler you will be adding air bubbles to the tank (back presure from the muffler) .

you want it hooked to the line that curves to the top of the tank. also if you are using a plug to plug the fill line off make sure it is sealing good and not sucking air.



bassman

shawntoast

10-4 ...I'll make sure I've got it right when I put it back in. and by the way, you're right about the bad experience thing. I live in a small town and the club operated flying fields are limited and all are associated with the bad experience, except for one small grass field nearby and I have been meaning to stop by and introduce myself, but when I have time nobody is there, and when someone is there I don't usually have the time. But I do need too, hell its less than 5 miles from my place. I just have plenty of room to fly over my hayfield and keep a grass runway mowed here at the house! I'm just a very independent person, and don't normaly like to ask paople for help. Although I could've saved myself thousands of dollars by not being so stubborn.(I also fly helis) thanks again man, I'll keep you posted.

dbacque

My Feedback: (3)

You said you checked all the lines but have you opened the tank and checked the fuel line to the clunk?

shawntoast

yeah, I'v had it all apart, and it all looks ok. I bet I had the wrong line on the muffler like bassman said, I haven't taken it back apart since he mentioned it, but I bet thats the problem. I'll try it again later in the week. Thanks for the reply though.

shawntoast

Hey bassman, You were right, the lines were plumbed wrong on the tank! I switched them around like you said and she runs fine, just have to get it tuned back in. I broke the manuals back out and found the ball park starting point for te needle valves, I think I can get there from here! You've been a great help man. thanks again

submikester

My Feedback: (6)

Did you check the tank for leaks? Pinch the fuel feed line and blow into the vent - see if air leaks anywhere. The lines can leak, the button on the front of the tank and leak or it can even split.

bassmanh

My Feedback: (5)

shawn,

glad to hear you got it fixed, now get it tuned and think about getting on the buddy box with someone and so you can get soloed and have fun flying





bassman

jaka

Hi!
If you see bubbles coming in the fuel line it is sure sign of a tank leak! That simple!
Some advise.
Use a use a 8-10oz tank and a 11x6,11,5x6 or 12x4 even a 12x6 APC prop.
Glow plug: OS 8 or Enya 3.
Fuel: 5-10% nitro and be sure to padd that tank with lots of soft foam.
And last ...be sure to use a 2-clunk system, that's "Uni-Flow ", which is the next best tank system for sport flying, next to the Tettra "Bubbleless" tank system.
Good luck!

pt19 flyer

My Feedback: (1)

hi
going to ask you a dumb question OK? have you balanced your prop? what you describe leads me to believe it is a vibration problem or tank not padded enough to avoid bubbling in tank. wrap tank with a couple layers of foam padding, check prop balance and I t hink you said you had replaced all fuel lines. also I had a plane with a thin bulkhead where the motor was mounted which had enough flex to cause enough vibration to cause foaming fuel. epoxyed a 1/8 inch plywood plate to firewall and solved problem.

try these and hope it helps

good luck and happy flying

pt19 flyer

TedMo

Bassman: You have me perplexed on this tank problem. You are saying that if the line from muffler is going to bottom of tank he is adding air bubbles to tank (back pressure from muffler) I agree. However, that is what he wants in tank,pressure. I also agree the one from muffler should be the one that goes to top of tank. However, what is going into tank through that one, back pressure from muffler, same think. Only difference is one is creating bubbles in fuel because it is immeressed in fuel but those bubbles should not be going into fuel supply line. If that were so we would have that problem when we were inverted. Anyway That's my consensus.