Although it's mostly about car engines this technique can be applied to other nitro powered models also. For airplanes a common practice is to prime by closing the air inlet on the carburetor instead of the exhaust. That is a better method but on cars the air filter is in the way.
What you'll need
(note: you can support this blog by buying from the provided links)
A nitro rc car (or other nitro powered rc model). An affordable way to start this hobby is to get a first nitro car form Hobbyking. They have a very small 1:16 scale model and a 1:8 scale nitro model from the international warehouse. The local warehouses also have 1:5 scale models but you really shouldn't get started with these monsters.
Transmitter: You'll need a transmitter and receiver and a lot of batteries. Also for safety reasons don't forget to set your failsafe and get one of these electronic protectors in case your batteries run out.
Nitro fuel: This you'll have to buy at your local hobby shop. This is flammable stuff so won't be shipping from international sellers. 18% nitro or anything around that will do.
Glow plug lighter: These ones from hobbyking only need a single AA battery. You can also get a starter kit that comes with a rechargeable lighter in most cases. The kits often have a bottle to transfer fuel into the fuel tank. A quicker alternative is a fuel pomp like these.
Let's get started with a picture to mark some parts.
green is where the glow plug should go
blue is where you fill the fuel tank, to close properly after filling
red is the exhaust pipe, to cover while primiing
yellow is the carburetor covered with an airfilter and the high speed needle sticking up (the low speed is on the side and the idle screw is the small one around the air inlet of the carburetor, I'll get that covered in the tuning article)
Before you do anything you should always check your electronics. Always use fully charged batteries for both receiver and transmitter! You don't want to see your model crash into something totally out of control just because you forgot to charge your batteries. And thats without any third party damage in the best case!
Always power up your transmitter first and then you receiver on the model. This way you'll have control when needed. Check that the servo's turn in the right direction and step away from the model to check range.
Next step is to fill the fuel tank. A brand new engine should run idle and rich for about 4 to 5 tanks. This is called breaking in an engine. This allows for the moving parts to get used to each other. So that is what well do for no, you can use factory settings in most cases. More information about tuning the engine will follow in another post.
Make sure to close the fuel tank tight when done so no air can escape. All the fuel lines and the engine itself should also be checked for any leakage. Otherwise you won't be able to prime the engine or it will run badly or not start at all. Air can escape through an open fuel tank, a glow plug not screwed in tight and leakage in the fuel lines. Other leakages are less common on a brand new engine.
Prime the Engine
To be able to start a cold engine you should get some fuel into the combustion chamber first. Otherwise the glow plug won't have anything to ignite. This is called priming. Older full scale engines used to have buttons for this also.
Now on our models some have a button but in most cases you'll have to give slight throttle, cover the exhaust pipe with your finger and pull the starter cord a few times. If done properly you should see the fuel travel to the engine.
If not check that you don't hear any sisssss like sounds since that would indicate loss of compression. Also don't forget to open up the throttle. And the biggest screw on top of the carburetor can also be closed.
You'll have to pull the starter cord a few times for the fuel to reach the engine. Knowing how much fuel is required for the first start is something you'll learn by practice only. If too much fuel got in the engine will be flooded, more about that later.
Light the Glow Plug
OK you're ready to lit the glow plug now. Close the throttle completely (that is the idle stand) and put the glow plug lighter on top of the glow plug. Make sure it's properly charged. Easiest way to check is to put a glow plug in it and see if the plug glows properly.
Glow plugs won't work for a lifetime. When wear out is visible just replace it. It's a good idea to replace the glow plug if you tried everything else and still don't have a properly starting engine.
And this is when you should pull the starter cord to get the engine started. Don't pull the cord all the way out so you don't damage it. Instead pull short and hard to get a proper revolution.
If you primed the engine well and the glow plug is glowing the engine should start in 3 pulls at max. If not there are a few things you can check.
- Sisss sounds are an indication of loss of compression, check for leaks
- No smoke or puffs at all are a sign that the glow plug is not glowing, get it out and check by putting it in the lighter
- Nitro flying around is an indication that you flooded the engine. Take the plug out and pull a few times more to get excessive nitro out (be careful for your eyes). Also waiting a few minutes can help
- In some cases a little throttle is required to start properly