What are the standard techniques and/or checks to be applied on a glow/nitro engine that refuses to start ?  What is the step by step diagnosis procedure to handle them ?

PS: The question was purposefully posed as "glow or nitro" engine (even though they are called one or the other interchangeably), since it would help people search using either of those words.

Let me start off with some categories of problems/issues that may cause this condition. 

1) Fuel supply related issues: Like a broken or disconnected clunk line in the tank, a carb with dust in it, lack of priming etc. 

2) Tuning and usage issues : Incorrectly setup main or low speed needles, incorrectly setup throttle servo endpoints, not enough charge in the glow ignitor etc

3) Engine health issues :  Bad glow plug, lack of compression etc.

There are many more, others may please pitch in. Each category has many issues that fall under it.  If someone can post a generic step by step procedure for diagnosis, that will be great.

In general, I have noticed that car engines tend to be a bit wild in terms of such issues.  Is that a generally true assessment ?

I have tried to summarize a list of symptoms I have seen when learning how to tune nitros. I am still learning by trial and error. If there is anything wrong in the below, please correct. This is from a beginners perspective. Experts may find this silly.

This is something I have learned after hours of reading and interacting with experts like Aravind and other chennai flyers.

If you are having issues with your nitro engines, these are the symptoms you need to look out for. These are for car engines, but guessing its same for aircraft as well

1. High speed needle - lean

Symptoms: Overheating, engine cutting out at full throttle.

2. High speed needle - rich

Symptoms: Boggy performance. lots of smoke. sluggish high speed throttle response

3. Low speed needle - rich

Symptoms: Sluggish acceleration, excessive unburned fuel spitting from the exhaust, engine cutting off when glow ignitor is removed

4. Low speed needle - lean

High idle. The vehicle will try to move while sitting still.

Always start tuning with the High Speed needle and then move to the Low speed needle. You lean the HSN, its also leans the LSN like a garden hose.

Some engines like Thunder tiger have a mix metering or change over screw. It doesnt require any change after default setting.

To set idle, I usually tune it last. I press the brakes and turn out the screw till the engine stalls, then turn it back a bit. If you engine is cutting when applying brakes, increase idle.

Please add if you have any other indicators to help tune better and faster.

Thank you Ajo.

Can someone post details on how to detect if an engine has been over-primed / flooded, and the solutions for the same. 

Quote from: anwar on September 26, 2009, 08:17:35 PM
Thank you Ajo.

Can someone post details on how to detect if an engine has been over-primed / flooded, and the solutions for the same.  

Simple in Cars.

Symptom:
Engine will refuse to turn over, if you have pull start, it will be very hard and refuse to move.

Solution
Remove glow plug and pump out excess fuel by turning the engine by pulling or roto start. I sometimes turn the car upside down to shake out the excess fuel.

My Method
Always carefully watch the fuel move thru the line and reach the carb while priming the engine. I have installed this cute blue primer bulb on my nitros to help prime better.

Cool gadget just for priming    And your car looks very clean ! Is it fairly new, or you take care of it meticulously 

When you turn engine upside down, does the extra fuel exit via the muffler ? In other words, can fuel already in the chamber, of say a 2stroke glow engine, exit back via the carb or does it have to exit only via the muffler ?  As that would determine how you should hold the engine (like with the muffler hole of the engine pointing downward).  How about having the throttle fully open, and hold it with the carb pointing down ?

So is removing the glow plug sort of the the only sure fire fix for a flooded engine ?  Is there a way "that works most of the time" to get the extra fuel out without opening/removing the glow plug ?

Turning the engine upside down and then rocking the prop(dunno what it would be in car) back and forth ensures that the fuel is in the combustion chamber. Thereafter turn the engine to its side so that when the piston is lowered the fuel comes to exhaust outlet and then turn it in a manner that the muffler outlet is pointing down, This will help in draining out the fule. Repeat this process till the time you do not get the locked feeling and then close the needle/disconnect the fule line and start once started the engine would die out soon as it will run dry.

Another method is to backflip the engine while pointing the exhaust down and then turing the muffler outlet down does a good job of draining the excess fuel.

Procedure one works like a charm for all two and four strokes. The second one I have not tried on 4T so opinions are welcome.
But the easiest way it to take off the plug and spin the engine. But then too much of screwing in and out of parts certainly is not good as you are likely to screw up during one such procedures 

Very useful information ! 

If ones notices the glow engine does not start, one of the things they need to check if fuel is coming into the carb/engine.  Let us say that they noticed no fuel inflow into the engine when they turn their props with a starter.

As this point, what all should we investigate ?

Also, how does this troubleshooting work for "pumped" versus "non-pumped" engines ?

When on the first start of the day. Open the venturi completely and choke with finger while rotating the prop. One should see the fuel being sucked into the engine. (Do this with glow disconnected). If you can not reach the venturi, choke the muffler outlet while rotating the prop does the same thing. Do not over do this as this would lead to engine going rich. The moment you see fuel entering carb give one more turn and no more. Remove your finger from venturi/exhaust hole and turn over two-three times to distribute the fuel charge. Now you are ready to connect glow and flip/whirl the prop for a start.
If the fuel is not coming in to the engine check the following

1. Check that your fuel lines are connected to the engine
2. See that needle is open appropriately
3. Check if the line is connected to the tank
4. Check for any severe kinks in the line (if the kink is not severe fule may flow but the engine would starve of fuel when started and die but still suck in fuel under choke)
5. Check that you have no pin holes in the line (if you have you will see bubbles in the fule line)
6. Check for block in your pipe line
7. Check for blocks in your carb (to do this and 6 above, remove the needle out of housing, and blow in from the pressure pipe, you should see fuel gushing out of needle housing and be careful of the fuel sparying in your eyes/body do this at your own risk and no liabilities are accepted. if it does, fuel passage upto this point is clear, if not you need to investigate the block. Put the needle back open up two three turn and repeat the process and fuel should now come out of carb venturi, if it does the entire fuel passage is clear. But this will also certainly lead to your engine being flooded so you now have to remove the excess fuel.)  
8. Above all did you check that you have fuel in the tank???

9, Make sure that you have the engine muffler/exhaust open... 

Usually there are 3 (some times 2) inlets/outlets to the fuel tank.  How should they be connected and if the engine is not starting because somebody connected them wrong, how to diagnose the right connections without removing the whole tank assembly ?

Ye who knowth about nitro engines, please pitch in this thread.  It would be great to see this thread become a one-stop resource for all nitro engine starting problems ! 

Ye who obviously knowth the answers to thy own questions, please answer 

With a three or two line setup and tank full to the brim it is pretty difficult to tell what's wrong. As all line will suck in fuel. The pressure line will be in fuel, and so will be the fill and clunk. So the best way to check is fill half or less. You have to play the elimination game.

With two line setup here is how you go
With the plane upright and fuel tank half filled check which lines suck in fuel if out two. If both are sucking in you have the pressure tube upside down in the tank to confirm this invert the plane and check again only one should do and that is your feed line the other is pressure line.

With the three line set up here is how you do it
Same process but now two lines should draw fuel if all three do you need to take out the tank and thereafter it is easy to determine with the tank held against a bright light.

If only two do your non drawing line is the pressure line. Mark it for identification.
Now to seperate feed from fill line invert the plane and only one line should draw fuel. Which ever does is your feed line.

The same exercise can be performed with all lines disconected from engine and hanging free. Empty the tank and when you fill from pressure line fuel will flow out from feed and fill lines, but while filling from feed or fill line it will not from pressure line till the time the tank is full. So you now have pressure line identified. Invert the plane and do the same exercise and you now have the dry line as your feed line. Oh BTW while doing this exercise one of the two line free (the ones from which you are not filling) has to be blocked one by one. 

Quote from: RotorZone on September 30, 2009, 09:03:21 PM
Ye who obviously knowth the answers to thy own questions, please answer  

You do have to play spoil-sport, don't you  

Just play along....    It is good for the RC masses !

My Ki-100 had a 46FX engine which was worn out and it always used to deadstick after a couple of circuits. I then replaced the tank with a uni-flow setup and it worked fine. I was able to fly it for longer duration but then it used to deadstick again. Nevertheless, the uniflow setup has worked well.

Here is an explaination of the uniflow tank setup -> http://www.fraserker.com/heli/uniflow/how_uniflow_works.htm

Cool info on the uniflow setup 

My brother ran into a pressure problem on his first 4 stroke pumped engine. Since it was pumped, there was no feedback from the muffler into the tank. So all he had was one line to refuel (which was shut during flight), and the line that feeds the carb/engine. During flight as fuel was being sucked out, a vaccuum started forming in the tank (there is no route for air to come in), and he ran into multiple issues.  Finally, he added a third line, with a small aluminium (or may be copper, can't remember) tube inside the fuel line, and left it open all the time. It was bent with a sharp angle, in order to discourage the fuel from coming out. Worked fine after that, and no fuel ever escaped through it, as there was always more fuel being sucked into the engine, and all the open pipe ever did was to supply air into the tank.  I will try to get a photo of the setup.

Moving on.....  so let us say I have ensured that fuel is coming into the carb, and the carb is free of dirt.  I have also established that the plug and hotshot/ignitor are working fine (if you take the plug out, insert it in the igniter, and it glows reddish orange with some strength, it should be OK).  I have ensured that the low speed and high speed needles are not fully closed. But the engine still refuses to start. 

Where do we go next ?

Oh! That brings us to the question. Who is/are the RC elite?

With a two line  set up you would know the moment you started to fuel. It would - immediately - start to spill out of the "pressure line.

Quote from: flyingboxcar on October 01, 2009, 05:55:31 PM
Oh! That brings us to the question. Who is/are the RC elite?

http://dictionary.cambridge.org/define.asp?key=25209&dict=CALD     

I couldn't explain it any better     Everyone on this forum are part of the "RC masses", that is what "I personally believe" (which is a phrase immortalized by a certain "Miss South Carolina" as shown in the clip below).



We still need to get back to the original/real topic though ! 

The question which was asked was "who are the elites of this forum" not "what is elite"
And Anwar never knew or even suspected that you openly/secretly considered yourself to be equivalent to a beauty contestant. But alas your comparision on "I personally beleive front" forces me to come to this conclusion.

Wish you had clarified the "of this forum" part    And even then, I inadvertantly replied to that also, that there are no elites here, as "I personally believe" !

You should see "Miss Congeniality"   I am certainly among the "light-hearted masses", not in any uptight group. "Quoting someone" and "equating of personality" are pretty unrelated concepts to the masses, but do those mundane details matter among friends !?!?

Now back to the question at hand    If fuel is coming in, the needles are open and the plug is fine, where does one look when the engine still doesn't start ?!?!? Any takers ?

If the plug is lit right, fuel is flowing in and the engine still refuses to start (that is starts speeds up and shuts down or yuu get uneven and jerky running) now is th time to check for appropriate high speed needle opening. Keep it in between 1 1/2 to 2 turns from fully closed and it should start.
If not you need to check for proper compression. Your cylinder and piston should not have any deep scoring and scrtaches if you have a ringed engine you may not be able to feel the compression on a cold engine here you also need to check if the psiton ring is not stuck or broken which is best done with engine dismantled.
  If even compression is right and all the above steps have been carried out you have one really sick engine which needs to be dismantled to check for real cause   

Thanks again Captain for one of the most useful threads on this site 

You mentioned that 1.5 to 2 turns open (from the fully closed position) is a good default to start with on the main needle (except for an engine that is brand new and not broken in, closer to 3 turns may be better). What would be a good such default on the low speed needle ?  Or is it dependent on the brand in any way ?