ENGINE RUNNING Part 2&3

Why Won’t My Engine Run? Part 2.

 

Part 1 contained a series of quick checklists, which could help to solve your engine problems. Part 2, again taken from the original by Alex Whittaker, considers some of these problems in more detail.

 

Fuel. There are generally less problems with a good quality commercial fuel, however it is possible to get satisfactory results by mixing your own provided the manufacturers recommended mix is used. This is usually 16-20% oil/methanol mix. Smaller engines, less than 25, can benefit from an     addition of 5-20% nitro. This aids prompt starting, keeps them running cooler and improves throttling. Larger engines are often less critical about needle valve setting with the addition of a small amount, up to 5%, of nitro.

Is the fuel fresh? Methanol is hygroscopic, (absorbs moisture from the atmosphere) and a poorly sealed container will enable water to get into the fuel.

Don’t mix 2-stroke with 4-stroke fuel.

Is the fuel clean and free from debris and is there a filter on the container delivery line? Both are essential.

 

Fuel Tank. The relative position of the tank is critical. Most experts suggest the tank centre line and carb’ jet should be in line, but anything up to 1/2 inch lower is usually acceptable. The tank should be supported by insulation to reduce vibration/fuel foaming when the engine is running.

Is the internal pipe-work correct? Assuming a two-line system (fill and vent) the fill is connected to the carb and the vent to muffler pressure nipple. The two bent metal tubes through the bung have to be correctly orientated, the vent tube should face upwards, to just underneath the top of the tank and the fill tube horizontal or slightly down.

The fill metal tube should have a fuel pipe with clunk attached. The clunk should be free to move in all directions without restriction. However heavy arrivals or other incidents can cause the clunk to fall forwards and become trapped. To avoid this a short length of metal tube can be included in the internal fuel pipe.

Once the internal pipe-work has been completed it is often prudent to complete a pressure/leak test before the tank is installed. This can easily be carried out by connecting a football inflator/pump to one of the inlet fuel lines and blocking off the other. Light pressurising with the tank held under water should reveal any leaks, but don’t over pressurise.

 

Fuel Lines.

These need to be of the correct bore for the engine size and muffler/carb nipples and free from any dirt or silicon blockages.

Fuel lines should not be too long or have sharp bends between tank and engine.

In line filters. There is considerable debate whether these are desirable. If your fuel has been filtered before it goes into the tank and the tank/pipe-work has been cleaned there should be no need for an in line filter. A blocked filter at this point will cause the engine to stop or behave erratically.  

 

Carburettor.

Major carb issues causing poor starting or running usually fall into three categories i.e. blockages, settings or leaks.

Blockages can usually be cleared by removing the needle valve, attaching the football inflator/pump and a short length of pipe to the carb inlet nipple and pump away. 

Always start of with the manufacturers recommended settings and make adjustments in small increments allowing time for the engine to settle down before making further adjustments. Too rich is usually better than too lean.

Often the main problem with an erratic carb is unwanted air leaking into the atomised fuel destroying the correct mixture. A thorough inspection when the engine is running may indicate air bubbles or fuel leaks due to loose unions or nuts. If the problem is leakage in the barrel of the carb, then substitution may be the only answer.

A loose needle valve clip may be allowing the valve to rotate when the engine is running.

If the problems can’t be solved try using a carb from a different engine or ask someone who knows!!

 

Plugs and Glow Starters.

Flat glow start and power panel batteries are the most common culprit for poor starting. Glow start batteries should be recharged before each session. Winding up the amps on the glow panel isn’t the answer. A cherry reddish/orange glow is what is required not a searing white element.

Some glow starts don’t fit correctly on the glow plug.

Changing the plug is always a good first option. Some old plugs can have a good glow but won’t start the engine.

Most engines will start/run better on a certain type of plug. The difficult part is finding which one!!

 

The real answer is there are no short cuts to success. Careful preparation and systematic fault-finding should help. If all else fails you may have to splash out and buy a new engine.

 

 

 

 

 

Why Won’t My Engine Run? Part 3.

 

The final part in this series has again been taken from the RCM&E magazine but this time the article was by the ‘Wizard of Oz’.

 

Keeping It Clean.

Having now got your engine starting easily and running reliably it is equally important to retain this by keeping the engine clean.

An engine corrodes inside due to heat and moisture. Overloading and lean tuning is the catalyst for chemical corrosion attack. The by-product of combustion is an acid soup mixed with water and this is the problem causing agent in four-strokes and, to a lesser degree, two-strokes. After flying your model you idle down and the engine cools. Moisture and soup are in the crankcase and stays there until you next use the engine.

To avoid prolonged corrosion, as you finish flying run your engine up to full operating temperature at full throttle and while it is running disconnect or block off the fuel pipe. The engine will use up the fuel and will then dry out using the residual heat.

To improve the process further squirt a good dose of synthetic oil (as used in the fuel mix) or commercial after-run oil into the breather of a four-stroke or the carb of a two-stroke. Give the engine a few spins and it should last for ages.

If you are not intending to use the engine for some time, remove the glow plug and squirt synthetic oil or 3in1 into the cylinder again giving the engine a few spins.