Practical Hand Book of Gas, Oil and Steam Engines / Stationary, Marine, Traction; Gas Burners, Oil Burners, Etc.; Farm, Traction, Automobile, Locomotive; A simple, practical and comprehensive book on the construction, operation and repair of all kinds of engines. Dealing with the various parts in detail and the various types of engines and also the use of different kinds of fuel.

by John B. Rathbun

(94) Operation of Timers.

Timers frequently cause misfiring which is generally due to dirt or oil getting between the contacts, or to the wear of the insulating walls W-W-W-W, or to the wear of the moving parts.

Dirt or gummy oil will prevent the contact coming together and completing the circuit, or will clog up the rollers or levers so that they cannot perform their functions properly. This will of course interfere with production of the spark.

The contacts and moving parts of the timer should be kept as clean as possible, all dirt and heavy oil being removed by means of gasoline at regular periods. Make a practice of cleaning out the timer at intervals not greater than one month; oftener if possible.

Parts subject to wear, such as the roller pin J and the bearings should be well lubricated, none but the lightest oil being employed for this purpose. Heavy grease will gum the contacts and cause trouble. There should be no rough places or shoulders on the contact sectors or on the walls W-W-W-W as roughness will cause the roller to jump over the high places which in turn result in misfiring. The remedy is to machine the surfaces of the sectors and walls by grinding or turning in the lathe. Care should be taken in this operation to have the interior perfectly smooth and the sectors perfectly flush with the walls. Repair black or burnt sectors immediately by grinding or sand paper.

Burnt spots or blackened surface on the contact sectors prevent good contact between roller and sector, sectors should show a bright, shining metallic surface.

Sometimes the insulation warps or swells above the contacts so that the roller jumps over the contacts without touching them, or if for any reason that contact is made under these conditions, it is of a short period and results in a poor spark.

Timers often make good contact when starting, or at low speed, and misfire badly at high speed. This will be caused generally by the contact sectors or insulation projecting beyond one another, the roller has time to make good contact at low speed but jumps over the sector at high.

The roller I may become rough or develop a flat stop which will cause it to jump over the contact occasionally, or it may become loose on its bearing pin J, causing intermittent misfiring.

The wearing or loosening of pins J and X result in poor contact. Should pin J fall out of the lever H, the roller would drop out of the fork and cause serious damage. This has happened in two cases to my knowledge.

Should the spring G weaken or break, contact will be made intermittently at high speed, and no contact at low. In this case it would probably be impossible to start the engine. In case the spring breaks, a rubber band may be used temporarily. Wire connections to the timer should be examined frequently as the continual back and forth movement tends to twist and loosen the wire. Use stranded or flexible wire for these connections, if possible.

Before removing the timer mark the hub and the shaft so that the hub can be properly replaced. If this is not done the engine will be out of time with the usual results of hammering or power loss.

Should the gears which drive timer shaft be removed, be sure and mark the teeth of both gears in such a manner that there will be no mistake possible in reassembling them. Mark a tooth on the small gear by scratching or with a center punch (the tooth selected should be in mesh with the large gear). Then mark the two teeth of the large gear that lay on either side of the marked tooth of the small gear. Thus it will be easy to locate the proper relative position of the two gears at any time.