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Old Jan 21, 2013, 01:29 AM
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Joined Jun 2007
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Help!
Evolution PTS is haunting me..

Hi guys, I have a problem with my little pts trainer engine. It's very strange to me, I can get it to start cold and run pretty well for a little while but then it dies like it is too rich. When you try priming the engine at first by putting your finger over the carb and turning the prop it does this weird thing when trying to suck the fuel up into the carb... It will start going up the line, maybe an inch or so, then drop straight back down into the tank! The fuel will never get all he way to the carb and stay, it always slowly goes back to the tank.. It causes the engine to take forever to start and I find myself blowing into the vent line until the carb is full and then pinching off the vent line until I can start it. I've looked at all of the lines and the tank itself and didn't see any holes, so I don't know where the loss of suction would be, I can make the engine run really well though, for a little while.. It's been crashed one time a long time ago and never put in a plane since. Could it be the gasket between the engine and the muffler? Or one of the o-rings in the HSN or carb? I'm willing to try anything, I'm going to make my own design plane once I get this thing running consistently. I'm a novice at best at nitro engines so I don't know too much, but I understand the mechanics Thanks for any input! Wishing you all the best
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Old Jan 21, 2013, 02:31 AM
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DarZeelon's Avatar
Israel, Ramat HaSharon
Joined Nov 2003
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FC,


Your engine is behaving perfectly normal (fuel flowing back and forth...)...
All engines do that.

Prime your engine instead by opening the throttle fully, plugging the exhaust outlet with your finger and turning the prop over rapidly, until after the fuel reaches the carburettor inlet.
Doing this has the exact same affect as blowing into the vent-line.

After that, flip the prop several times, close the throttle to idle (about 1-1.5 mm open), hook-up the glow clip and back-flip the prop against compression, or use an electric starter to start the engine.

It is a glow engine, or a methanol engine (nitro engine is a misnomer, which names the engine after one of the additives of its fuel).

If the engine dies after a little while, it is either too rich, or too lean.

Run it at high RPM and pinch the fuel-line. It it speeds up and then dies, it is much too rich.
If it dies outright, it is too lean.
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Old Jan 21, 2013, 09:48 AM
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Quote:
Originally Posted by DarZeelon View Post
FC,


Your engine is behaving perfectly normal (fuel flowing back and forth...)...
All engines do that.
Just wondering though, is it normal for the fuel to flow back out of the carb once it's in it? It would be primed and then slowly make its way back to the tank.. I'm only asking because I didn't think that it did it before.

Thank you!
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Old Jan 21, 2013, 10:41 AM
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FC,


Only fuel that is still in the fuel-line or in the nozzle can flow back.

The carburettor does not have any 'chamber' in which fuel is kept...
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Old Jan 21, 2013, 10:43 AM
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Israel, Ramat HaSharon
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Open the high-speed needle one turn, to see if the engine keeps running after it starts.

It sounds lean from your description.
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Old Jan 21, 2013, 11:17 AM
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United States, MI, Macomb
Joined Apr 2009
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Check to see if your pressure nipple on the muffler is not plugged. Use a piece of wire to make sure its open.

Just a thought.
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Old Jan 21, 2013, 11:35 AM
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United States, Mt, Bozeman
Joined Jan 2012
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My EVO 61 has a habit of doing the flowback trick as well. I just keep the tx handy, prime, then throttle down (idle ish) while still holding finger on the exhaust. The fuel will no longer flow back into the tank. Always fires by the third flip this way.

*The problem is exaggerated if the more open the high speed needle is.
(not to say you are too rich or lean)
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Old Jan 21, 2013, 01:23 PM
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Thanks everyone. All very good ideas and I will be sure to keep them in mind. I will give it a try and get back to you.

Ps I don't have an electric starter, and it's on a test rig that is throttled my hand, so it makes things a little more...interesting lol
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Old Jan 21, 2013, 04:10 PM
The Prez....... again
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United States, IA, Rockwell
Joined Jul 2011
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I see your tank level is way low and the fuel level is even lower.

If you raise the center line of the tank to about 1/4 inch to 3/8 inch below the needle valve you will much better luck. Best is to duplicate the position of the tank as it would be installed in the plane. Then you can set your low and high speed mix very close to the final position as everything will be very close to the final installation in the airframe.

ken
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Old Jan 22, 2013, 12:47 AM
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Makes sense. I'll try that too!
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Old Jan 22, 2013, 03:00 AM
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Quote:
Originally Posted by kenh3497 View Post
i see your tank level is way low and the fuel level is even lower.

If you raise the center line of the tank to about 1/4 inch to 3/8 inch below the needle valve you will much better luck. Best is to duplicate the position of the tank as it would be installed in the plane. Then you can set your low and high speed mix very close to the final position as everything will be very close to the final installation in the airframe.

Ken
++1

The center-line of the fuel-tank should be the same height to 3/8th inch lower than the carburettor.
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Old Jan 22, 2013, 08:40 AM
The Prez....... again
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United States, IA, Rockwell
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Forgot to mention. The tank should be horizontal instead of vertical.

Ken
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Old Jan 22, 2013, 10:05 AM
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Quote:
Originally Posted by kenh3497 View Post
Forgot to mention. The tank should be horizontal instead of vertical.

Ken

++1

Of-course.
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Old Jan 25, 2013, 12:24 AM
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Joined Jun 2007
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Ill make a new motor mount that will work right! Thanks guys, im excited to get this thing running!
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