Aviation Engines: Design—Construction—Operation and Repair

by Victor Wilfred Pagé

Broken Magneto Carbon Brush.
Broken Lead Wire.
Broken Ground Wire.
Battery Ignition Systems.
Water on High Tension Magneto Terminal.
Main Secondary Cable Burnt Through by Hot Exhaust Pipe (Transformer Coil, Magneto Systems).
Particle of Carbon Between Spark Plug Points.
Magneto Short Circuited by Ground Wire.
Magneto Out of Time, Due to Slipping Drive.
Water or Oil in Safety Spark Gap (Multi-cylinder Magneto).
Magneto Contact Breaker or Timer Stuck in Retard Position.
Worn Fiber Block in Magneto Contact Breaker.
Binding Fiber Bushing in Contact Breaker Bell Crank.
Spark Advance Rod or Wire Broken.
Contact Breaker Parts Stuck.

Motor Runs Irregularly or Misfires

Loose Wiring or Terminals.
Broken Spark-Plug Insulator.
Spark-Plug Points Sooted or Oily.
Wrong Spark Gap at Plug Points.
Leaking Secondary Cable.
Prematurely Grounded Primary Wire.
Batteries Running Down (Battery Ignition only).
Poor Adjustment of Contact Points at Timer.
Wire Broken Inside of Insulation.
Loose Platinum Points in Magneto.
Weak Contact Spring.
Broken Collector Brush.
Dirt in Magneto Distributor Casing or Contact Breaker.
Worn Fiber Block or Cam Plate in Magneto.
Worn Cam or Contact Roll in Timer (Battery System only).
Dirty Oil in Timer.
Sticking Coil Vibrators.
Coil Vibrator Points Pitted.
Oil Soaked Magneto Winding.
Punctured Magneto or Coil Winding.
Distributor Contact Segments Rough.
Sulphated Storage Battery Terminals.
Weak Magnets in Magneto.
Poor Contact at Magneto Contact Breaker Points.

DEFECTS IN ELECTRICAL SYSTEM COMPONENTS

To further simplify the location of electrical system faults it is thought desirable to outline the defects that can be present in the various parts of the individual devices comprising the ignition system. If an airplane engine is provided with magneto ignition solely, as most engines are at the present time, no attention need be paid to such items as storage or dry batteries, timer or induction coil. There seems to be some development in the direction of battery ignition so it has been considered desirable to include components of these systems as well as the almost universally used magneto group. Spark-plugs, wiring and switches are needed with either system.

SPARK-PLUGS
DEFECT		TROUBLE CAUSED	REMEDY
Insulation cracked.		Plug inoperative.	New insulation.
Insulation oil soaked.		Cylinder misfires.	Clean.
Carbon deposits.		Short circuited spark.	Remove.
Insulator loose.		Cylinder misfires.	Tighten.
Gasket broken.		Gas leaks by.	New gasket.
Electrode loose on shell.		Cylinder misfires.	Tighten.
Wire loose in insulator.		Cylinder misfires.	Tighten.
Air gap too close.		Short circuits spark.	Set correctly.
Air gap too wide.		Spark will not jump.	Set points 1⁄32′′ apart.
Loose terminal.		Cylinder may misfire.	Tighten.
Plug loose in cylinder.		Gas leaks.	Tighten.
Mica insulation oil soaked.		Short circuits spark.	Replace.
MAGNETO
DEFECT		TROUBLE CAUSED	REMEDY
Dirty oil in distributor.		Engine misfires.	Clean.
Metal dust in distributor.		Engine misfires.	Clean.
Brushes not making contact.		Current cannot pass.	Strengthen spring.
Distributor segments worn.		Engine misfires.	Secure even bearing.
Collecting brush broken.		Engine misfires.	New brush.
Distributing brush broken.		Engine misfires.	New brush.
Oil soaked winding.		Engine misfires.	Clean.
Magnets loose on pole pieces.		Engine misfires.	Tighten screws.
Armature rubs.		Engine misfires.	Repair bearings.
Bearings worn.		Noisy.	Replace.
Magnets weak.		Weak spark.	Recharge.
Contact breaker points pitted.		Engine misfires.	Clean.
Breaker points out of adjustment.		Engine misfires.	Reset.
Defective winding (rare).		No spark.	Replace.
Punctured condenser (rare).		Weak or no spark.	Replace.
Driving gear loose.		Noise.	Tighten.
Magneto armature out of time.		Spark will not fire charge.	Retime.
Magneto loose on base.		Misfiring and noisy.	Tighten.
Contact breaker cam worn.		Misfiring.	Replace.
Fibre shoe or rolls worn (Bosch).		Misfiring.	Replace.
Fibre bushing binding in contact lever (Bosch).		Misfiring.	Ream slightly.
Contact lever return spring broken.		No spark.	Replace.
Contact lever return spring weak.		Misfiring.	Replace.
Ground wire grounded.		No spark.	Insulate.
Ground wire broken.		Engine will not stop.	Connect up.
Safety spark gap dirty.		No spark.	Clean.
Fused metal in spark gap.		No spark.	Remove.
Safety spark gap points too close.		Misfiring.	Set properly.
Loose distributor terminals.		Misfiring.	Tighten.
Contact breaker sticks.		No spark control.	Remove and clean bearings.
Magneto switch short-circuited.		No spark.	Insulate.
Magneto switch open circuit.		No engine stop.	Restore contact.
STORAGE BATTERY
DEFECT		TROUBLE CAUSED	REMEDY
Electrolyte low.		Weak current.	Replenish with distilled water.
Loose terminals.		Misfiring.	Tighten.
Sulphated terminals.		Misfiring.	Clean thoroughly and coat with vaseline.
Battery discharged.		Misfiring or no spark.	New charge.
Electrolyte weak.		Weak current.	Bring to proper specific gravity.
Plates sulphated.		Poor capacity.	Special slow charge.
Sediment or mud in bottom.		Weak current.	Clean out.
Active material loose in grids.		Poor capacity.	New plates.
Moisture or acid on top of cells.		Shorts terminals.	Remove.
Plugged vent cap.		Buckles cell jars.	Make vent hole.
Cracked vent cap.		Acid spills out.	New cap.
Cracked cell jar.		Electrolyte runs out.	New jar.
DRY CELL BATTERY
DEFECT		TROUBLE CAUSED	REMEDY
Broken wires.		No current.	New wires.
Loose terminals.		Misfiring.	Tighten.
Weak cell (7 amperes or less).		Misfiring.	New cells.
Cells in contact.		Short circuit.	Separate and insulate.
Water in battery box.		Short circuit.	Dry out.
TIMER
DEFECT		TROUBLE CAUSED	REMEDY
Contact segments worn or pitted.		Misfiring.	Grind down smooth.
Platinum points pitted.		Misfiring.	Smooth with oil stone.
Dirty oil or metal dust in interior.		Misfiring.	Clean out.
Worn bearing.		Misfiring.	Replace.
Loose terminals.		Misfiring.	Tighten.
Worn revolving contact brush.		Misfiring.	Replace.
Out of time.		Irregular spark.	Reset.
INDUCTION COIL
DEFECT		TROUBLE CAUSED	REMEDY
Loose terminals.		Misfiring.	Tighten.
Broken connections.		No spark.	Make new joints.
Vibrators out of adjustment.		Misfiring.	Readjust.
Vibrator points pitted.		Misfiring.	Clean.
Defective condenser	} rare.	No spark.	Send to maker for repairs.
Defective winding
Poor contact at switch.		Misfiring.	Tighten.
Broken internal wiring.		No spark.	Replace.
Poor coil unit.		One cylinder affected.	Replace.
WIRING
DEFECT		TROUBLE CAUSED	REMEDY
Loose terminals anywhere.		Misfiring.	Tighten.
Broken plug wire.		One cylinder will not fire.	Replace.
Broken timer wire.		One coil will not buzz.	Replace.
Broken main battery wire.		} No spark.	Replace.
Broken battery ground wire.
Broken magneto ground wire.		Engine will not stop.	Replace.
Chafed insulation anywhere.		} Misfiring.	Insulate.
Short circuit anywhere.

Carburetion System Faults Summarized

Motor Starts Hard or Will Not Start

No Gasoline in Tank.
No Gasoline in Carburetor Float Chamber.
Tank Shut-Off Closed.
Clogged Filter Screen.
Fuel Supply Pipe Clogged.
Gasoline Level Too Low.
Gasoline Level Too High (Flooding).
Bent or Stuck Float Lever.
Loose or Defective Inlet Manifold.
Not Enough Gasoline at Jet.
Cylinders Flooded with Gas.
Fuel Soaked Cork Float (Causes Flooding).
Water in Carburetor Spray Nozzle.
Dirt in Float Chamber.
Gas Mixture Too Lean.
Carburetor Frozen (Winter Only).