ENGING RUNNING Part 1

Why Won’t My Engine Run? Part 1.

 

The following is a series of diagnostic checklists, prepared by Alex Whittaker and published in the RCM&E Magazine during 2005. If these don’t help your engine to start and run smoother I suggest you go electric. If this is unthinkable then take up golf or gliders. Golf is probably more fun!!

 

1. Pre Start Checks.

 

Propeller.

- Check for correct size and pitch from engine manufacturers recommendations

Note

- A heavier prop will often run better than a light one due to the flywheel effect as will a prop that has the same pitch and diameter but a broader blade.

- A balanced prop will out perform an unbalanced one and is safer.

- A larger dia prop will often run more smoothly and quietly but will rev more slowly.

- The prop must exactly match the engine crankshaft. Do not be tempted to run a prop that wobbles.

 

Glow Plug.

- Plugs come in three types ’hot’, ‘medium’ and ‘cool’. You may need to experiment to get best performance but start with the manufacturers recommended plug.

- A plug that glows may not necessarily give a good start.

- 4-Stroke engines usually need a special plug.

 

Fuel Tank and Lines.

- The centreline of the tank and the carb main jet to be approximately at the same height.

- Positive pressure from the muffler will usually give better running but make sure the air can get in to push the fuel out.

- Is the clunk line (fuel in) the correct length and is the clunk free to move to the top and bottom of the tank?

- Check all lines are free from small debris and small leaks. You may need to carry out a pressure test to confirm the latter. A filter on the fuel line in the container is a good start.

 

Fuel.

- Use the engine manufacturers recommended formulation.

- Is the fuel fresh, clean and filtered?

- Poor engine starters may benefit from a ‘shot’ of nitro’ fuel primed into the carb.

- 2-Stroke engines should not be run on 4-Stroke fuel.

 

2. Basis Starting Procedure.

 

Propeller.

- Ensure the prop is secured at the 2 o’clock pos’n (when viewed from the front) as it comes up to compression. Is there compression?

- If fitted, is the spinner secure and correct to take an electric starter?

- Check the rubber snubber on the starter is the correct way round.

 

Fuel Tank and Lines.

- Fill tank and check for leaks, loose connections or blockages and ensure lines are correctly connected to the muffler and carb.

 

Needle Valve.

- Start with manufacturers recommended setting. If this is not available try between 2-1/2 and 3-1/2 turns open (anticlockwise) from the closed position.

- Choke the engine with a finger sealed over the venturi for two or three full turns of the prop.

- Check that fuel is reaching the carb, if not try opening the needle valve a further half turn.

 

Setting the Throttle Position.

- This can vary but try 1/3 to 1/2 open.

 

Locked/Flooded Engine.

- Remove plug and turn prop to remove excess fuel. Replace plug and washer.

 

Glow Starter.

- Using a glow starter, with a recharged battery, make sure it is secure on the engine and not wobbly.

 

Starting.

- Unless you’ve got a strong wrist and a ‘chicken stick’ an electric starter is the easiest provided the battery is charged!!

 

When Running.

- Peak the engine out by turning the needle valve slowly clockwise and then richen the fuel by turning the valve anti-clockwise 2 or 3 clicks.

- Don’t run the engine too lean. This causes most of the performance problems.

 

Inverted Engines.

- From time to time these can cause problems. If so try the following technique.

With the plane parked on its wheels.

- Set the needle valve for a normal slightly rich start.

- Remove the glow plug to drain out any fuel, which may be wetting it.

- Close off the fuel line to the carb with a clip or long-nosed forceps.

- Fill the tank with the plane still standing on its wheels.

- Re-fit and energise the glow plug.

- Remove the clip/forceps and apply the starter.

 

3.Troubleshooting.

 

Engine Won’t Start.

- Duff glow plug.

- Too few amps on panel or flat glow battery.

- Insufficient fuel in tank or fuel blockage. Check fuel lines/carb and flush out.

- Engine flooded. Remove plug and expel excess fuel.

- Crank speed too low. Check starter battery.

 

Engine Starts, Burps but Won’t Run.

- Poor glow or flooded engine.

 

Engine Starts but Fades.

- Mixture too rich. Adjust by turning needle valve clockwise in small increments.

 

Engine Starts but Stops Abruptly.

- Fuel starvation. Check fuel tank and fuel lines/carb for blockages. Check needle valve setting. Adjust anti-clockwise.

 

Engine Stops When Glow Start Removed.

- Duff glow plug.

- Mixture too rich. Adjust needle valve clockwise.

- Cold Engine. Leave glow plug connected a little longer.

 

Engine Hunts/Wavers.

- Air leak in carb or fuel lines. May need a pressure test to confirm.

- Variable blockage. Check carb, fuel tank and fuel lines. Flush out.

 

Engine Won’t Pickup.

- Slow running needle. Refer to manufacturers handbook for adjustments, with engine stopped.