The match box thingy is a relay. There are two of them mounted together behind the ECU. One is the fuel pump relay, the other is the main relay. The fuel pump relay on the Scrambler provides power only to the fuel pump. The main relay provides power to the fuel pump relay, the coils and injectors, the starter solenoid and a feed back to the ECU. If the main relay fails virtually nothing works.
However, the problem is unlikely to be the relay itself. The relay will be chattering (the sound you hear) because of a bad connection. When the relay switches current is drawn by the items which are powered through it. If there is a bad connection the voltage across the relay drops causing it to switch off. The current drain stops and the voltage immediately rises again, so the relay switches on again, the voltage drops, the relay switches off, and so on and so on.....
Check the battery terminals are tight and if you can get at it the battery earth to the frame. Check also the condition of fuse no. 5 (20A) as the power to the main relay comes through it. A bad connection can be due to oxidation on the blades of the fuse. Removing and refitting the fuse a couple of times can wipe this off and restore the connection.
If these checks fail try swapping the 2 relays, they are both the same, and see if there any change.
