GUARD 2299558 - Caterpillar

Illustration 3. New and former gaskets used in control shutoff group.During the initial (first) production (construction) of the 760 kPa (110 psi) groups, the former 5N3199 Gasket was used. Identification of these groups which have the former gasket can be made by the code marks on the identification plate which is on the hydramechanical shutoff. A change has been made to this code since introduction of the 760 kPa (110 psi) groups. A 1E15 code was used first and then changed to a number sequence code. All 760 kPa (110 psi) groups with the 1E15 code, and those with a number sequence code below 00313 have the former 5N3199 Gasket. If a problem is found with operation of the rack shutoff on one of these groups, remove the 5N3199 Gasket and install the new 5N8227 Gasket.
Rack Shutoff Group
A new 9N4053 Spring is used in place of the former 5N5758 Spring in the rack shutoff group. The new spring is approximately 57.2 mm (2.25") long and the former spring is approximately 106.7 mm (4.20") long. The new spring has less force than the former spring, and permits more positive operation of the cylinder. See Illustration 4. With the former spring, oscillation of the cylinder piston was possible during tests for low oil pressure or emergency manual shutoff conditions (when the red knob is pulled while the air inlet shutoffs are held or fastened open). If this oscillation is found during test procedures, the spring can be checked as a possible cause. If replacement of the spring is made and oscillation does not stop, a check valve may be needed. See the November 3, 1980 Service Magazine, page 5.
Illustration 4. New and former springs used in fuel rack shutoff.Test Procedures
All the tests shown in the paragraphs which follow are normally made at low idle engine rpm. The tests can be made at any engine rpm, but tests at a higher rpm are not necessary. If the shutoff operates correctly at low idle rpm, the systems will operate faster at a higher rpm.
While most of the tests make it necessary to stop the engine, the drive coupling, override valve and override actuator (palm valve) tests can be made during engine operation under full load conditions. This makes it possible to check the drive coupling when conditions do not permit the engine to be stopped. Under these conditions, the recommendation is to make this test every 500 SMU as a minimum check because a coupling failure will prevent operation of all control circuits.
Illustration 5 shows the primary components and circuits, and can be used as a reference during test procedures. Illustrations 6 and 7 show the locations of shutoff components on the engine.
Illustration 5. Schematic diagram for control shutoff.Regular Maintenance Test (Every 500 SMU)
This test must be made every 500 SMU to be sure the hydramechanical shutoff operates correctly. To make the test, run the engine and pull the red emergency knob. This activates the control, and the engine must stop. If