BRIEF SUMMARY OF HINTS FOR STARTING ENGINE
First make sure that all cylinders have compression. To ascertain this, open pet cocks of all cylinders except the one to be tested, crank over motor and see that a strong opposition to cranking is met with once in two revolutions. If motor has no pet cocks, crank and notice that oppositions are met at equal distances, two to every revolution of the starting crank in a four-cylinder motor. If compression is lacking, examine the parts of the cylinder or cylinders at fault in the following order, trying to start the motor whenever any one fault is found and remedied. See that the valve push rods or rocker arms do not touch valve stems for more than approximately 1⁄2 revolution in every 2 revolutions, and that there is not more than .010 to .020 inch clearance between them depending on the make of the motor. Make sure that the exhaust valve seats. To determine this examine the spring and see that it is connected to the valve stem properly. Take out valve and see that there is no obstruction, such as carbon, on its seat. See that valve works freely in its guide. Examine inlet valve in same manner. Listen for hissing sound while cranking motor for leaks at other places.
Make sure that a spark occurs in each cylinder as follows: If magneto or magneto and battery with non-vibrating coil is used: Disconnect wire from spark-plug, hold end about 1⁄8 inch from cylinder or terminal of spark-plug. Have motor cranked briskly and see if spark occurs. Examine adjustment of interrupter points. See that wires are placed correctly and not short circuited. Take out spark-plug and lay it on the cylinder, being careful that base of plug only touches the cylinder and that ignition wire is connected. Have motor cranked briskly and see if spark occurs. Check timing of magneto and see that all brushes are making contact.
See if there is gasoline in the carburetor. See that there is gasoline in the tank. Examine valve at tank. Prime carburetor and see that spray nozzle passage is clear. Be sure throttle is open. Prime cylinders by putting about a teaspoonful of gasoline in through pet cock or spark-plug opening. Adjust carburetor if necessary.
LOCATION OF ENGINE TROUBLES MADE EASY
The following tabulation has been prepared and originated by the writer to outline in a simple manner the various troubles and derangements that interfere with efficient internal-combustion engine action. The parts and their functions are practically the same in all gas or gasoline engines of the four-cycle type, and the general instructions given apply just as well to all hydro-carbon engines, even if the parts differ in form materially. The essential components are clearly indicated in the many part sectional drawings in this book so they may be easily recognized. The various defects that may materialize are tabulated in a manner that makes for ready reference, and the various defective conditions are found opposite the part affected, and under a heading that denotes the main trouble to which the others are contributing causes. The various symptoms denoting the individual troubles outlined are given to facilitate their recognition in a positive manner.
Brief note is also made of the remedies for the restoration of the defective part or condition. It is apparent that a table of this character is intended merely as a guide, and it is a compilation of practically all the known troubles that may materialize in gas-engine operation. While most of the defects outlined are common enough to warrant suspicion, they will never exist in an engine all at the same time, and it will be necessary to make a systematic search for such of those as exist.
To use the list advantageously, it is necessary to know one main trouble easily recognized. For example, if the power plant is noisy, look for the possible troubles under the head of Noisy Operation; if it lacks capacity, the derangement will undoubtedly be found under the head of Lost Power. It is assumed in all cases that the trouble exists in the power plant or its components, and not in the auxiliary members of the ignition, carburetion, lubrication, or cooling systems. The novice and student will readily recognize the parts of the average aviation engine by referring to the very complete and clearly lettered illustrations of mechanism given in many parts of this treatise.
Ignition System Troubles Only
Motor Will Not Start or Starts Hard
Loose Battery Terminal.
Magneto Ground Wire Shorted.
Magneto Defective (No Spark at Plugs).
Broken Spark Plug Insulation.
Carbon Deposits or Oil Between Plug Points.
Spark-Plug Points Too Near Together or Far Apart.
Wrong Cables to Plugs.
Short Circuited Secondary Cable.
Broken Secondary Cable.
| Dry Battery Weak. | ⎫ | Battery Systems Only. |
| Storage Battery Discharged. | ⎬ | |
| Poor Contact at Timer. | ⎮ | |
| Timer Points Dirty. | ⎭ |
| Poor Contact at Switch. | ⎫ | Battery and Coil Ignition System Only. |
| Primary Wires Broken, or Short Circuited. | ⎮ | |
| Battery Grounded in Metal Container. | ⎬ | |
| Battery Connectors Broken or Loose. | ⎮ | |
| Timer Points Out of Adjustment. | ⎮ | |
| Defects in Induction Coil. | ⎭ |
Ignition Timing Wrong, Spark Too Late or Too Early.
Defective Platinum Points in Breaker Box (Magneto).
Points Not Separating.
Broken Contact Maker Spring.
No Contact at Secondary Collector Brush.
Platinum Contact Points Burnt or Pitted.
Contact Breaker Bell Crank Stuck.
Fiber Bushing in Bell Crank Swollen.
Short Circuiting Spring Always in Contact.
Dirt or Water in Magneto Casing.
Oil in Contact Breaker.
Oil Soaked Brush and Collector Ring.
Distributor Filled with Carbon Particles.
Motor Stops Without Warning
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.