REF: the MPU set up.. what every one has offerd is correct, however, the tip of the MPU should hit onto the top of a flywheel tooth when your setting this up, for that you might well have to use some tool of your choice to move a "tooth" into the center area of your target range. Most often a larger flat blade screwdriver will be a good fulcrum tool to accomplish this. A near sure check of the operation of the MPU is go back and check with the mpu removed for open/close of the MPU, set up your meter so you can read between the two output wires, then pass over anything steel over the MPU tip, you will or should expect to see the opening and closing of the MPU being reflected on your meter scale, in this instance or check an analog type meter is the very best to observe this operation, digital meters take a frustrating time to scale the event onto the display screen.
Now earlier you were trying to read the output up on or near one of the relay landing points, you were cautioned to first go directly to the mpu and read it at the mpu, now that we have a confirmed good mpu now go on upstream following the wiring and see if you keep your signal along the wiring route.
Press on, best of luck: mac/mc