Last weekend I flew a flight and landed and then tried to take off and the engine would die when I would advance the throttle and get up to speed. After that I wouldn't be able to start it. I changed the fuel tank nozzle because the pressure hose wasn't any good in the old one. Today I went flying again and I took off fine and flew around for about 10 minutes and the I went into a climb and slammed the stick to full throttle and the engine died. I landed and tried to start it again and it wouldn't start. I lessened the needle valve and it started up but it would surge. I then tried to advance the throttle and it died instantly. I tried to start it again and the same thing happened. Then I tried to start it again and it wouldn't start so I increased the needle valve and it started and sounded good. I then advanced the throttle and when I got up to flying speed it died. The same thing happened again. I'm dumbfounded on what to do so I thought i'd ask on here. Would the engine run if the fuel lines got crossed? Would that be possible.

Which engine?

have you adjusted the low speed needle?

Certainly the engine will not run if the fuel lines get mixed up. Here's a good diagnostic: Start the engine. Hold the plane upright -- pointed straight up into the air. Advance the throttle to full open. Watch the fuel line going into the carburetor. You should NOT see any air bubbles going from the tank into the carb. Also, by pointing straight up, you are testing the needle valve setting. If the needle valve is too lean, the engine may run allright, but when you point it up, it may sag and quit. this is telling you to open the needle valve. But you have already tried that, so I suspect you may have air leak problems. One of the most common problems is getting air leaks in either the fuel line or the carburetor or around the cylinder backplate or head. Sometimes, after a hard landing or crash, the fuel pickup clunk inside the tank gets forced into the front of the tank. this clunk should always remain in the back of the tank.

Sounds like you may be a bit lean on the low end. Is the engine excessivly hot after it stalls (too hot to touch)?

Steve

P.S. Nope. It wont run if the lines are crossed, not for 10 minutes anyway.

I agree with the previous suggestions about your low-end needle. I had exactly the same behaviour with my first engine - it started promptly, idled smoothly and throttled well in the pit. Then, after taxiing out to the runway, waiting at the hold point for the guy in front, and then moving to the take-off point, I would advance the throttle and it would surge and die.

Sometimes, just to be obnoxious, it would let me get airborne and then die. I got pretty good at dead-stick maneuvering and landing, for a newbie and it's a miracle my trainer was not smashed (it is an LT-40, so that huge wing and the wonderful glide came in handy).

A couple of the "old hands" in my club spent a lot of time over several attempted flying sessions working on the needles, but couldn't get it settled down. It was obvious to everyone that the engine was "loading up" while running at low throttle, and this left it way too rich so the burst of fuel when the throttle opened just killed the engine.

Finally, I found some instructions on RCU from a member called "Dauntae" about [link=http://www.rcuniverse.com/forum/m_694681/anchors_694681/mpage_1/key_tuning/anchor/tm.htm#694681]low-end needle adjustments[/link]. I took the engine off the plane and bolted it to a test stand, and spent about an hour carefully and systematically tuning the low end needle (and the high end too, of course) according to Dauntae's instructions.

When I put the engine back, it ran sweet and smooth and has given no dead-stick landings since then.

So, why did the "old hands" fail to get it adjusted? Well, I found it needed quite a LOT of low-end adjustment and it didn't show much improvement over the first half- to 3/4 turns. The "old hands" had assumed that the low end needle was pretty close, and of course were hesitant to keep turning it when small adjustments gave no obvious improvement or degradation of performance.

From now on, every new engine is getting the treatment BEFORE it goes on a plane. Maybe this is the problem with your plane too. FWIW.

I had this problem today. The engine would run fine then die on lift off. My problem was a loose muffler so check that out.

asuming that this engine is broken in and has been running fine for awhile before acting up ,several things could be the cause.
1.crossed fuel lines.
2. new tank fuel pick up too close to rear of tank should be about 3/8 inch away from rear wall.
3.clogged fuel filter if used.
4.dirt or forien matter in spray bar.
5.loose rear and/or rear cover screws.
6.pinched fuel/pressue line
7.foaming fuel tank.
8.bad fuel/alcohal absorbs water like crazey so if jug was not kept capped tightly in a humid/damp area could be contaminated.
9.bad glow plug/just because it glows does not mean it is good,element could be covered with a clear glaze preventing proper ignition or element could be deformed slightly.
10.if muffler pressure is not used vent line could be plugged.
long list but there are alot of other things that could be the cause,listed the most common and some of the easiest fixes.let us know what you find.

The engine is an O.S. 46 LA. Where is the low-speed needle and the high-speed needle? I looked in my manual and it said that if you tilt it up while holding it and it quits then tighten the air-bleed screw half a turn.

Frager,


More likely than not, you have a fuel tank installation problem; not an engine problem.

A low fuel tank, long fuel lines, clunk at the front, vibration transmitted to the tank and other problems will 'advertise' themselves in what you are experiencing.


First, make sure the fuel tank's center-line is level with the carburettor's jet (+ 9 mm, or 3/8" ), with the model in level flight attitude.
If not, correct this before going any further.

Also, make sure the tank is as close as possible to the engine; the fuel line from the tank to the needle should not be more than 2.5-3" long.

After that, you can adjust your engine perfectly.

I think DarZeelon has given you the best advice. Since it was once running correctly until you made some pluming changes, chances are your problems are fuel delivery problems, not needle valve adjustments.

I've been running the engine and it seems as though I have the problem solved. I guess i'll have to take it out and fly it to see for sure. I tightened up the air-bleed screw a couple of turns. My engine is having some bad vibration problems when it's at idle. When I increase the throttle the vibration stops. How can I help this? I have the engine on an Aircore kit and if any of you have experience with those they have the engine, tank and all the other onboard gear on one long piece of would inside the fuse so i'm worried about the vibration damaging my radio gear.

balance the prop ans spinner,should help to eliminate the vibration.could also be you are running the engine a bit rich open the air bleed 1/8 of a turn and see if that helps but ballance the prop first