TM 5-3895-346-14
SHOP NOTES
ENGINE OVERHAUL
CHECK ENGINE STARTING SWITCH
If difficulty in starting motor engagement has been experienced in a vehicle which has been repowered by a
diesel engine, check to see if the key-type starting switch on the instrument panel has been retained.
Key-type starting switches are usually not capable of carrying the current required for heavy-duty diesel engine
starter solenoids. The excessive voltage drop in the solenoid circuit restricts the solenoid pull and results in
failure of the starter to engage and crank. When tooth abutment occurs and the switch is turned off and on
several times, breaking of the solenoid current causes burning or welding of the switch contacts.
Install a push button type starting switch which is capable of making, breaking, and carrying the solenoid
current without damage (refer to Engine Starting Switch in Instruments). Otherwise, a heavy-duty magnetic
switch should be used in the solenoid control circuit in addition to the key-type switch. The magnetic switch
must be capable of making and breaking at least 90 amperes in a 12-volt system; the key switch would then
carry no more than one ampere, which is sufficient to operate the magnetic switch.
ALIGNMENT TOOLS FOR TACHOMETER DRIVE COVERS AND ADAPTORS
Whenever a tachometer drive cover assembly or a tachometer drive adapter is installed on an engine, it is
important that the cover assembly or adapter be aligned properly with the tachometer drive shaft.
Misalignment of a tachometer drive shaft can impose a side load on a tachometer drive cable adapter resulting
in possible gear seizure and damage to other related components.
To establish proper alignment, use one of the three tools in set J 23068. Because of the many different
combinations of tachometer drive shafts, covers, and adapters, it is not practical to itemize specific usages for
each tool. When confronted with an alignment job, test fit each tool to determine which provides the best fit
and proceed to make the alignment with that tool as shown in Fig. 1.
Correct alignment is established when there is no tachometer drive shaft bind on the inside diameter of the tool
when one complete hand rotation of the engine is made.
Figure 1. Checking Tachometer Drive Shaft Alignment
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