SPRING 5K7409 - Caterpillar

Introduction
The electric protection system for spark ignited engines is available in two different junction (J) box arrangements. The J box arrangements are used on either an Energize To Shutoff (ETS) or Energize To Run (ETR) system depending on the type of gas shutoff valve used and how it is wired to the J box terminal strip. Both J box arrangements offer full engine system protection (OP, WT, OS). One of the J box arrangements is completely independent as purchased, while the other arrangement needs an outside switchgear to make it functional.In these J box arrangements the time delay relay must arm the system before it becomes effective. Once the system is armed, a problem with any of the engine systems that are monitored will cause the gas shutoff valve to be activated. This will immediately stop fuel to the engine and cause engine shutdown. At the same time, the magneto is connected to ground to stop current flow to the spark plugs.The full protection system arrangement monitors the engine from starting through 118% of rated speed.Component Description
Electronic Speed Switch (ESS)
7W2743 or 4W2218 ELECTRONIC SPEED SWITCH (ESS)
1. Verify button. 2. Reset button. 3. "LED" overspeed light. 4. Seal screw plug (overspeed). 5. Seal screw plug (crank terminate). 6. Seal screw plug (oil step).The Electronic Speed Switch (ESS) is designed with controls built into a single unit to monitor several functions at the same time. Two different ESS switches are used, but the only difference is mounting hole location. The functions that the ESS monitors are:Engine Overspeed (OS)
This is an adjustable engine speed setting (normally 118% of rated speed) that prevents the engine from running at a speed that could cause damage. This condition will cause a switch to close that shuts off the fuel to the engine and connects the magneto to ground to stop current flow to the spark plugs.Crank Termination (CT)
This is an adjustable engine speed setting that signals the starter motor that the engine is firing and cranking must be terminated. When the speed setting is reached, a switch will open to stop current flow to the starter motor circuit. The starter motor pinion gear will now disengage from the engine flywheel ring gear.Oil Step Latch
This feature of the ESS is not adjustable. After terminal ESS-17 has been energized by loss of engine oil pressure, the oil step switch (OPSS) contacts are now held in the closed position. This will maintain OPSS in closed position until 2 seconds after the engine has completepy stopped. This action will prevent the shutoff from resetting below oil step speed.Engine Step Oil Pressure
This is an adjustable engine speed setting that gives protection to the engine from a failure caused by too little oil pressure for a specified speed range. To maintain desired protection through the complete speed range of operation, two different oil pressure switches are used one with a high pressure rating (OPS2), and one with a low pressure rating (OPS1).Once the step oil pressure speed setting is made,