Automotive Systems

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Injector Timing

Injector Timing

Whenever an injector has been removed and reinstalled or a new injector has been installed in an engine, the injector must be timed and the control rack positioned.

The injector plunger is timed by the fact that it meshes with a flat area on the internal rack gear inside the injector body. It is also timed to the fuel control rack—a dot on the gear that is centered between two dots on the injector control rack. Actual effective length that the plunger moves down in its bushing is controlled by the height of the injector follower above the injector body.

To time an injector properly, adjust the injector follower to a definite height in relation to the injector body (fig. 5-26). This will vary according to the size of the injector being used. This dimension is given in the engine tune-up section of the service manual. Current timing pin dimensions can also be found stamped on the valve rocker cover emissions decal. Be certain that you select the proper timing pin gauge (fig. 5-27); otherwise, the engine will run rough and fail to perform properly under load. In addition, continued operation of the injector set at the wrong timing height can result in engine damage.

All the injectors can be timed in firing-order sequence during one full revolution of the crankshaft on all two-cycle engines. A four-cycle engine requires two revolutions of the crankshaft. The sequence for injector timing is as follows:

1.      The governor speed control lever should be in the IDLE position. If a stop lever is provided, secure it in the STOP position.

2.      Rotate the engine crankshaft, using an engine barring tool, until the exhaust valves are fully depressed on the cylinder that you wish to set the injector. If a barring tool is not available, a 3/4inch-square drive socket set with a suitable socket to fit over the crankshaft pulley will also do.

3.      Insert the small end of the timing pin (gauge) into the hole provided in the top on the injector body, with the flat portion of the gauge facing the injector follower.

4.      Gently push the gauge by holding the knurled stem with the thumb and forefinger towards the follower. There should be a slight drag between the gauge and the follower.

5.      If this cannot be done, loosen the injector pushrod locknut and adjust it until the drag of the gauge (slight feel) has been determined. old the pushrod and tighten the locknut. Recheck the feel, and, if needed, readjust.

6.      When hot setting this adjustment, wipe off the top of the injector follower and place a clean drop of oil on it. When properly adjusted, the gauge should just wipe off the oil film from the follower when the slight drag is felt.

7.      Time remaining injectors in the same manner.

Figure 5-26.—Timing fuel injectors.

Figure 5-27.—Timing gauge.

Published by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy

Copyright 2001-2004 SweetHaven Publishing Services
All rights reserved