SEAL-O-RING 5W1876 - Caterpillar

Electronic Control Side of the Air Starting System
Move the start control switch to activate the starting solenoids. Listen for the sound of the engagement of the air starter motor pinion with the flywheel gear.
If the sound of the engagement can be heard, the problem is with the Air Side of the Air Starting System. Proceed to the Air Side of the Air Starting System.
If no sound of the engagement can be heard, the problem could be with the Electronic Control Side of the Air Starting System.
Illustration 1 g06236265
(1) Connector
(2) Solenoid valve
(3) Electronic control board
Check the electrical system by disconnecting the leads from the solenoid valve (2) at connector (1). Set the multimeter in the "DCV" range. Measure voltage across the disconnected leads that connect to the starting switch.
A voltage reading shows that the problem is in the solenoid valve (2) or the air starting motor. Go to Step 2 of Air Side Of The Air System.
A "ZERO" reading shows that the problem is in the control switch or the problem is in the wires for the control switch.
Fasten the multimeter lead to the start switch at the terminal for the wire from the battery. Fasten the other lead to a good ground.
A "ZERO" reading indicates a broken circuit from the battery. With this condition, check the circuit breaker and wiring.
The problem is in the control switch if either a voltage reading is found at the control switch or if a voltage reading is found in the wires from the control switch to the control valve.Air Side of the Air Starting System
Illustration 2 g06236268
(1) Connector
(2) Solenoid valve
(3) Electronic control board
(4) Air hose
Activate the control switch. If the engagement of the air starter motor pinion with the flywheel ring gear can be heard, then remove the small air hose (4) from the side of the starter.
Full air pressure comes from the end of the air hose (4) when the control switch is activated. The pilot operated relay valve (RLVA) is worn or the air starting motor is damaged. The RLVA is built into the air starting motor.
If no air pressure comes from the end of the air hose (4), then the problem is in the pinion nose housing for the air starting motor or the solenoid valve.
The sound of the engagement of air starter motor pinion with the ring gear is not heard when the control switch is activated. Voltage was measured at the control valve. Remove solenoid valve (2).
If no air comes from solenoid valve (2), the solenoid valve is worn.
If the air comes from solenoid valve (2), then the problem is internal passage of the pinion nose housing for the air starting motor.