There are three components to the stop system, not including the wiring
. These are:
- the EVC button panel
- the MDI box mounted on the side of the exhaust
- the stop solenoid mounted on the rear side of the high pressure injection pump
When the stop button is pushed, 12 volts is applied to the purple wire running from the button panel to the MDI box where it activates an internal relay. The relay in turn activates the stop solenoid by applying 12 volts to the purple wire which runs from the MDI box thru a two wire connector to the stop solenoid.
When the solenoid is energized a plunger extends from the relay and pushes the injection pump fuel
rack to the " no fuel" position stopping the engine.
Most of the system can be checked fairly easily. Starting at the solenoid, unplug the two wire connector and unscrew the solenoid from the back of the injection
pump. With the solenoid removed you should see the plunger either flush with the body of the solenoid or protruding slightly. Momentarily connect the wiring
to a 12v source...black is ground and purple is positive. When energized the plunger should extend about 17-18 mm and then spring load back into the body of the solenoid when the voltage is disconnected. If the solenoid reacts properly, check the wiring harness from the two wire connector back to the MDI box for any opens or shorts.
Next check the EVC button panel. Disconnect the panel from the system. The purple wire in the harness controls the stop function. You need to use an ohm meter to see if the stop button is functioning. Normally the circuit is open but pushing the stop button should close the circuit between the purple wire and the black wire. If this checks good, check the wiring harness between the button panel and the MDI box for any shorts or opens.
Unfortunately, checking the MDI box requires a special "break out box" to check functions, but in any event the relays within the box are not serviceable. If everything else checks out good the problem is almost certainly within the MDI box and it will have to be replaced.