If the machine will not start the trouble, can only be located by a systematic search. It is always best to look over the ignition system first, then see if there is any gasoline in the carburetor. It will often take some time to find the trouble. However, if the engine once starts there is little difficulty in locating the trouble as there will always be an indication which should point to the source of trouble. The great difficulty with inexperienced drivers is that they do not reason out the matter carefully before attempting to remedy it. Also an inexperienced man usually looks for trouble in the same place no matter what the indication may be. Nearly all difficulties arise from one of three sources, ignition, carburetion, or engine. These are outlined in the following table. The trouble is located by the trouble it gives the driver. =I. Engine misses=: A. Ignition. 1. Plugs. a. Short circuit. b. Broken porcelain. c. Too large a gap. 2. Cable. a. Broken. b. Grounded. 3. Instrument. a. Dirty carburetor. b. Interrupter points on magneto. B. Carburetor. 1. Water in carburetor. 2. Dirt in the line. 3. No pressure or no gas. 4. Too lean a mixture. C. Engine. 1. Cold. 2. Valves sticking. =II. Back Fires Through Carburetor:= A. Ignition 1. Wired wrong. 2. Timed wrong. B. Carburetor. 1. Water in carburetor. 2. Dirt in line. 3. No pressure or no gas. 4. Too lean a mixture. C. Engine. 1. Valve sticking (Inlet). =III. Engine Knocks:= A. Ignition. 1. Retarded spark. Spark too far advanced. B. Engine. 1. Carbonized cylinders (pre-ignition). 2. Overheated engine. 3. Loose bearings. 4. Loose pistons. =IV. Engine Lacks Power:= A. Ignition. 1. Retarded spark. B. Carburetor. 1. Too rich a mixture. C. Engine. 1. Exhaust valve not seating. 2. Carbon in cylinder. 3. Overheated engine. 4. Lack of lubrication. 5. Governor connections sticking. D. Brakes. 1. Dragging. E. Clutch. 1. Slipping. =V. Engine Overheats.= A. Ignition. 1. Retarded spark. B. Carburetor. 1. Rich mixture. C. Engine. 1. Cooling system. a. Fan belt off. b. No water. c. No circulation. d. Anti-freezing mixture. 2. Carbonized cylinder. 3. Lack of lubrication. =VI. Engine Stops:= A. Engine and car stop gradually. 1. Trouble with fuel. B. Engine and car stop suddenly. 1. Mechanical trouble. C. Engine stops suddenly, car gradually. 1. Trouble with ignition. =VII. Engine Won’t Stop:= A. Ignition. 1. Cable. 2. Switch. B. Pre-ignition. 1. Carbon in cylinders. 2. Overheated engine.