| Explosions cease abruptly. | Break in ground wire, battery connections, switch lead. |
| Engine runs well slowly, but misses when speeded up. | Worn timer. | |
| Weak battery. | ||
| Faulty vibrator adjustment. | ||
| Faulty carbureter adjustment. | ||
| Fuel does not flow freely to carbureter. |
| Engine will not stop. | Preignition. | Glowing carbon or metal point in cylinder. | ||
| Engine too hot (see Cooling trouble). | ||||
| Engine does not deliver full power. | Faulty setting of valves. | |||
| Tight bearings or broken balls. | Indicated by excessive heating. | |||
| Back pressure. | Fouled muffler. | |||
| Dragging brakes. | ||||
| Friction in transmission. | ||||
| Faulty carburetion. | ||||
| Weak ignition. | ||||
| Weak compression. | ||||
| Overheating. | ||||
| Irregular miss. | Sticking valve. | |
| Slipping timer. | ||
| Loose half-time shaft. | ||
| Sticking air-valve. | ||
| Intermittent obstruction in spray nozzle. | ||
| Broken or weak valve-spring. | ||
| Loose connection. | ||
| Short circuit. |
| Engine noises. | Knocking. | Too much retard of spark. | ||
| Preignition. | ||||
| Worn bearings. | ||||
| Loose or cracked flywheel. | ||||
| Hissing. | Broken piston rings. | |||
| Leaking air inlet pipe or gasket. | ||||
| “Popping” in carbureter. | Leaking inlet valve. | |||
| Weak mixture. | ||||
| Excessive retard of spark. |
| Explosions weaken and cease. | Carbureter or fuel trouble. |
| Engine will not run slowly. | Weak magneto. | |
| Faulty carbureter adjustment. |
| Steady miss in one or more cylinders, (other cylinders firing normally). | Vibrator, timer, secondary circuit. |
| IGNITION. Jump spark, with single coil, battery secondary distributor. | Test primary circuit as described for system using coils and timer. | |||||
| Secondary may short circuit from | Fouled or worn distributor. | |||||
| Defective insulation. | ||||||