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.
| LOST POWER AND OVERHEATING | |||
| PART AFFECTED | NATURE OF TROUBLE | SYMPTOMS AND EFFECTS | REMEDY |
| Water Pipe Joint. | Loose. | Loss of water, heating. | Tighten bolts, replace gaskets. |
| Spark Plug. | Leakage in threads, insulation, or packing. | Loss of power. Hissing caused by escaping gas. | Replace insulation if defective, screw down tighter. |
| Compression Release Cock. | Leak in threads. Leak in fitting. | Loss of power. Whistling or hissing. | Tighten if loose. Grind fitting to new seating in body. |
| Combustion Chamber. | Crack or blowhole. Roughness. Carbon deposits. Sharp edges. | Loss of compression. Preignition. | Fill by welding. Smooth out roughness. Scrape out or dissolve carbon. |
| Valve Chamber Cap. | Leak in threads. Defective gasket. | Loss of compression. Hissing. | Remove. Apply pipe compound to threads and replace. Use new gasket or packing. |
| Valve Head. | Warped. Scored or pitted. Carbonized. Covered with scale. Loose on stem (two-piece valves only). | Loss of compression. | True up in lathe. Grind to seat. Scrape off. Smooth with emery cloth. Tighten by riveting. |
| Valve Seat. | Warped or pitted. Covered with carbon. Foreign matter between valve and seat. | Loss of compression. | Use reseating reamer. Clean off and grind valve to seat. |
| Valve Stem. | Covered with scale. Bent. Binding in guide. Stuck in guide. | Valve does not close. Loss of compression. | Clean with emery cloth; straighten. True up and smooth off. free with kerosene. |
| Valve Stem Guide. | Burnt or rough. Loose in valve chamber. | Valve may stick. Action irregular. | Clean out hole. Screw in tighter. |
| Valve Spring. | Weak or broken. | Valve does not close. | |
| Valve Operating Plunger. | Loose in guide. Too much clearance between valve stem. | Valve action poor. Lift insufficient. | Replace with new. Adjust screw closer. |
| Valve Lift Adjusting Screw. | Threads stripped. Too near valve. Too far from valve. | Poor valve action. | Replace with new. Adjust with proper reference to valve stem. |
| Valve Lift Cam. | Worn cam contour. Loose on shaft. Out of time. | Not enough valve lift. Will not lift valve. Valve opens at wrong time. | Replace with new. Replace pins or keys. Set to open properly. |
| Cam-shaft. | Sprung or twisted. | Valves out of time. | Straighten. |
| Cam-shaft Bushing. | Worn. | Not enough valve lift. | Replace. |
| Cam-shaft Drive Gear. | Loose on shaft. Out of time. Worn or broken teeth. | Irregular valve action. | Fasten securely. Time properly. Replace with new. |
| Cam Fastenings. | Worn or broken. | Valves out of time. | Replace with new. |
| Cylinder Wall. | Scored, gas leaks. Poor lubrication causes friction. | Poor compression. Overheating. | Grind out bore. Repair oiling system. |
| Piston. | Binds in cylinder. Walls scored. Worn out of round. | Overheating. Poor compression. | Lap off excess metal. Replace with new. |
| Piston Rings. | Loss of spring. Loose in grooves. Scored. Worn or broken. Slots in line. | Loss of compression. Gas blows by. | Peen ring or replace. Fit new rings. Grind smooth. Replace. Turn slots apart. |
| Carbon in grooves. Insufficient opening. Binding on cylinder. | Overheating because of friction. | Remove deposits. File slot. Grind or lap to fit cylinder bore. | |
| Wristpin. | Loose, scores cylinder. | Loss of compression. | Fasten securely. Replace cylinder if groove is deep. |
| Crank-shaft. | Scored or rough on journals. Sprung. | Overheating because of friction. | Smooth up. Straighten. |
| Crank Bearings. Main Bearings. | Adjusted too tight. Defective oiling. Brasses burned. | Overheating because of friction. | Adjust freely, clean out oil holes and enlarge oil grooves. |
| Oil Sump. | Insufficient oil. Poor lubricant. Dirty oil. | Overheating. | Replenish supply. Use best oil. Wash out with kerosene; put in clean oil. |
| Water Space. Water Pipes. | Clogged with sediment or scale. | Overheating. | Dissolve foreign matter and remove. |
| Piston Head. | Cracked (rare). Carbon deposits. | Loss of compression. Preignition. | Weld by autogenous process. Scrape off carbon accumulations. |
| NOISY OPERATION OF POWER PLANT | |||
| PART AFFECTED | NATURE OF TROUBLE | CHARACTER OF NOISE | REMEDY |
| Compression Release Cock. | Leakage. | Hissing. | Previously given. |
| Spark Plug. | Leakage. | Hissing. | Previously given. |
| Valve Chamber Cap. | Leakage. | Hiss or whistle. | Previously given. |
| Combustion Chamber. | Carbon deposits. | Knocking. | Previously given. |
| Inlet Valve Seat. | Defects previously given. | Popping in carburetor. | Previously given. |
| Valve Head. | Loose on stem. | Clicking. | Previously given. |
| Valve Stem. Valve Stem Guide. | Wear or looseness. | Rattle or clicking. | Previously given. |
| Inlet Valve. | Closes too late. Opens too early. | Blowback in carburetor. | Previously given. |
| Valve Spring. | Weak or broken. | Blowback in carburetor. | Previously given. |
| Cylinder Casting. | Retaining bolts loose. Piston strikes at upper end. | Sharp metallic knock. | Tighten bolts. Round edges of piston top. |
| Cylinder Wall. | Scored. | Hissing. | Previously given. |
| Valve Stem Clearance. | Too much. Too little (inlet valve). | Clicking. Blowback in carburetor. | Previously given. |
| Valve Operating Plunger. Plunger Guide. | Looseness. | Rattle or clicking. | Previously given. |
| Timing Gears. | Loose on fastenings. Worn teeth. Meshed too deeply. | Metallic knock. Rattle. Grinding. | Previously given. |
| Cylinder or Piston. | No oil, or poor lubricant. | Grinding. | Repair oil system. |
| Cam. | Loose on shaft. Worn contour. | Metallic knock. | Previously given. |
| Cam-shaft Bearing. | Looseness or wear. | Slight knock. | Previously given. |
| Cam Fastening. | Looseness. | Clicking. | Previously given. |
| Piston. | Binding in cylinder. Worn oval, causes side slap in cylinder. | Grinding or dull squeak. Dull hammering. | Previously given. |
| Piston Head. | Carbon deposits. | Knocking. | Previously given. |
| Piston Rings. | Defective oiling. Leakage. Binding in cylinder. | Squeaking. Hissing. Grinding. | Previously given. |
| Wrist-pin. | Loose in piston. Worn. | Dull metallic knock. | Replace with new member. |
| Connecting Rod. | Wear in upper bushing. Wear at crank-pin. Side play in piston. | Distinct knock. | Adjust or replace. Scrape and fit. Use longer wrist-pin bushing. |
| Crank Bearings. | Looseness. Excessive end play. Binding, fitted too tight. | Metallic knock. Intermittent knock. Squeaking. | Refit bearings. Longer bushings needed. Insert shims to allow more play. |
| Main Bearings. | Looseness. Defective lubrication. | Metallic knock. Squeaking. | Fit brasses closer to shaft. Clean out oil holes and grooves. |
| Connecting Rod Bolts. Main Bearing Bolts. | Loose. | Sharp knock. | Tighten. |
| Crank-shaft. | Defective oiling. | Squeaking. | Previously given. |
| Engine Base. | Loose on frame. | Sharp pounding. | Tighten bolts. |
| Lower Half Crank-case. | Bolts loose. | Knocking. | Tighten bolts. |
| Fly-wheel. | Loose on crank-shaft. | Very sharp knock. | Tighten retention bolts or fit new keys. |
| Oil Sump. | Oil level too low. Poor lubricant. | Grinding and squeak in all bearings. | Replenish with best cylinder oil. |
| Valve Plunger Retention Stirrups. | Looseness. | Clicking. | Tighten nuts. |
| Fan. | Blade loose. Blade strikes cooler. | Clicking or rattle. | Tighten. Bend back. |
| Exhaust Pipe Joints. | Leakage. | Sharp hissing. | Tighten or use new gasket. |
| Crank-case Packing. | Leakage. | Blowing sound. | Use new packing. Tighten bolts. |
| Water Pipe. | Leaks. Loss of water. Clogged with sediment. | Pounding because engine heats. | Previously given. |
| Water Jacket. | Clogged with sediment. Walls covered with scale. | Knocking because engine heats. | Dissolve scale and flush out water space with water under pressure. |
| “SKIPPING” OR IRREGULAR OPERATION | |||
| PART AFFECTED | NATURE OF TROUBLE | SYMPTOMS AND EFFECTS | REMEDY |
| Compression Relief Cock. | Leak in threads or spigot. | Dilutes mixture with air, causes blowback. | Screw down tighter. Grind spigot to seat with emery. |
| Spark-Plug. | Leak in threads. Defective gasket. Cracked insulator. Points too near. Points covered with carbon. Too much air gap. | Dilutes mixture. Allows short circuit. No spark. | Screw down tighter. Replace with new. Set points 1⁄64′′ apart for magneto, 1⁄32′′ for battery spark. |
| Valve Chamber Cap. | Leak in threads. Defective gasket. | Dilutes mixture by allowing air to enter cylinder on suction stroke. | Previously given. |
| Combustion Chamber. | Carbon deposits. | Preignition. | Scrape out. |
| Valve Head. | Warped or pitted. Loose on stem. | Dilutes charge with poor air or gas. | Previously given. |
| Valve Stem. | Binding in guide. Sticking. | Irregular valve action. | Previously given. |
| Valve Seat. | Scored or warped. Cracked. Covered with scale. Dirt under valve. | Gas leak, poor mixture. Poor compression. Valve will not close. | Previously given. |
| Induction Pipe. | Leak at joints. Crack or blowhole. | Mixture diluted with excess air. | Stop all leaks. |
| Inlet Valve. | Closes too late. Opens too early. | Blowback in carburetor. | Time properly. |
| Exhaust Valve. | Opens too late. Closes too early. | Retention of burnt gas dilutes charge. | Time properly. |
| Valve Stem Guide. | Bent or carbonized. | Causes valve to stick. | Previously given. |
| Inlet Valve Stem Guide. | Worn, stem loose. | Air drawn in on suction thins gas. | Bush guide or use new member. |
| Valve Spring. | Weakened or broken. | Irregular action. | Use new spring. |
| Valve Stem Clearance. | Too little. Too much. | Valve will not shut. Valve opens late, closes early. | Adjust gap.009′′ inlet,.010′′ exhaust. |
| Valve Spring Collar Key. | Broken. | Releases spring. | Replace. |
| Cam. | Worn cam contour. Loose on shaft. Out of time. | Valve lift reduced. Does not lift valve. Valves operate at wrong time. | Previously given. |
| Cam-shaft Bearing. | Looseness or wear. | Valve timing altered. Valve lift decreased. | Replace. |
| Cam-shaft. | Twisted. | Valves out of time. | Previously given. |
| Cam Fastening. | Worn or broken. | Valve action irregular. | Replace with new. |
| Valve Operating Plunger. | Loose in guide. | Alters valve timing. | Replace with new. |
| Valve Plunger Guide. | Wear in bore. Loose on engine base. | Alters valve timing. | Replace or bush. Fasten securely. |
| Timing Gears. | Not properly meshed. Loose on shaft. | Valves out of time. Valves do not operate. | Retime properly. Fasten to shaft. |
| Piston. | Walls scored. | Leakage of gas. | Smooth up if possible. |
| Piston Head. | Carbon deposits. Crack or blowhole (rare). | Cause premature ignition. | Previously given. |
| Piston Rings. | No spring. Loose in grooves. Worn or broken. | Leakage weakens suction. | Previously given. |
| Cylinder Wall. | Scored by wristpin. Scored by lack of oil. | Gas leaks by. Poor suction. | Previously given. |