Usage:
3114, 3116, 3306, 3406 Truck Engines With Mechanical Fuel Systems
- SUPPLEMENT: 01/01/96
Truck Engine News, January 1996, Page 4, "Tamper Resistant Plugs And Tamper Resistant Bolts Used To Prevent Changes To Air Fuel Ratio Control (AFRC) Setting" The text between Illustrations 3 and 4 is not correct. The correct text follows.
SOME (built upon request only) 3406 Truck Engines with mechanical fuel systems will have new 128-7794 and 128-7796 Tamper Resistant Bolts on the AFRC and cover. Illustration 4 shows the locations of the new tamper resistant bolts.
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Starting in 1996, the EPA Emission Regulations require engines to be equipped with some type of tamper resistant device. All the above Emission Certified Mechanical Fuel System Engines will be equipped with tamper resistant bolts or a tamper resistant plug in the governor housing to NOT ALLOW UNAUTHORIZED changes to the AFRC setting. The following is a listing of the devices used by each engine size.
The 3114 and 3116 Truck Engines will have a tamper resistant plug in the governor housing to NOT ALLOW UNAUTHORIZED changes to the AFRC setting. There are two sizes of tamper resistant plugs being used. Illustration 1 shows the typical location of a 128-4786 Tamper Resistant Plug (7/8inch thread). Illustration 2 shows the typical location of a 128-4794 Tamper Resistant Plug (1 5/8inch thread).
If an adjustment is required on a 3116 Truck Engine equipped with a tamper resistant plug, a 131-5009 Wrench is required to remove and install the tamper resistant plug.
Illustration 1. Typical location of a 128-4786 Tamper Resistant Plug (7/8inch thread) in a governor housing.
Illustration 2. Typical location of a 128-4794 Tamper Resistant Plug (1 5/8inch thread) in a governor housing.
The 3306 Truck Engine will have new 128-7794 and 128-7796 Tamper Resistant Bolts on the high idle cover, AFRC, and cover. Illustration 3 shows the location of the new tamper resistant bolts.
Illustration 3. Location of the new 128-7794 (3) and 128-7796 (4) Tamper Resistant Bolts on 3306 Truck Engines.
The 3406 Truck Engines with mechanical fuel systems will have new 128-7794 and 128-7796 Tamper Resistant Bolts on the AFRC and cover. Illustration 4 shows the location of the new tamper resistant bolts.
Illustration 4. Location of the new 128-7794 (3) and 128-7796 (4) Tamper Resistant Bolts on 3406 Truck Engines with mechanical fuel systems.
Tamper Resistant Bolt Removal And Installation
If an adjustment is required on a 3306, or 3406 Engine equipped with tamper resistant bolts, the bolts must be removed. Use the procedure that follows to remove the tamper resistant bolts:
1. Use a 1U-5592 (118 degree) Drill Bit or a 1U-5634 (135 degree split point) Drill Bit to drill a 7/64inch hole in the center of the bolt to be removed
2. Use a 4C-3365 Screw Extractor (5/32-7/32inch), in the hole drilled in Step 1, to remove the bolt.
3. When installing a new tamper resistant bolt, tighten the bolt until the bolt head shears off [approximately 12 ± 3 N·m (9 ± 2 lb ft) for 1/4inch diameter tamper resistant bolts or 25 ± 6 N·m (18 ± 4 lb ft) for 5/16inch diameter tamper resistant bolts].
The table identifies the part numbers and sizes of available tamper resistant bolts.
