Maney good brands & types. What I use is A/C coil cleaner & small brush, #55 drill bit (eyeglasses) and dielectric grease.
If your mpem was "fried", nothing could disarm the DESS system and allow the coded tether to enter it's code into the mpem, which in turn would not allow a signal to reach the solenoid or even the starting button and circuits that are tied into the start button, like self diagnostic mode, the intreraction of the tether post, and above all, the ignition, and ignition pickup.
In other words, when the mpem IS fried, no electrical system can possibly work without jumping and by-passing the mpem completely. So, you might want to rethink that if you can even activate the starter motor using the start button.
go over every ground and positive connection in the coil box, starting with the electrical connector under the rubber sheild on top of the coil box. Do not forget to clean out and inspect the 15 amp fuse holder in there, as they can rot with corrosion causing a momentary loss of voltage going to the mpem. Once even a momentary disconnect happens, all starting systems and ignition immeadetly shut down and the mpem has to be armed again by removing the tether for a few seconds, then reattaching it to re-arm the dess & mpem. Once armed you have 33 seconds max time before it dis-arms again unless the engine is running. Ground cables and wires can rot from the inside out, wires can sever from terminals that are very hard to see, especially if you do not know where to look. There are 6 major ground connections that must be in good working condition, and not corroded or broken. One is the main black negative cable connected under the starter side of the motor on a 947 engine. Two are located on the lower left side of the mag cover oil pump under the bolt heads on the mag housing that connect the mag housing cover to the engine cases. ( all directions are looking at the motor from the rear of the motor ). One is in the connector on top of the coil box, one is inside the coil box to ground out the coil and solenoid and that connector wire loom on the lid of the coil box. The last "main grounding connections" are in the big AMP connectors that plug into the face of the mpem and the terminals that those grounding wires are attached to on the face of the mpem and inside of the AMP connectors. All others are located in the various other GM type connectors going to and from the tether post, start button activated circuits, buzzer, guages, VTS, TPS, ( if so equipt) and any other electrical accessories. Oh, and the fuse HOLDERS on the mpem can rot too.
Pretty much the same can be said of any power cable or wire, connector, ect. Like the plug on the face of the mag housing, coil box and power circuits inside the coil box or face of the mpem, ect. The "main ones" are interrelated to the mpem, tether, start stop button, ignition coil(s), solenoid and starter motor. And like a ground interruption, a power interuption will instantly shut off all electrical functions until re-armed. Bills86e
