Some time back, someone posted a problem they were having with their engine where they had fire only when they removed the spark plugs. What brings this subject to mind is that I just ran into this problem. What I want to bring up is that the sensor coils on the 73 thru 77 3, and 4 cylinder engines are adjustable. Rapair makes a ring guage to make this adjustment. The number of the guage is R553-9702, and appears to be made of molded plastic that slips down on the crank shaft taper. The engine I had showed 1, to 1 1/2 volts with the plugs in. After adjusting the sensors the voltage went to 3 1/2 - 4 volts, and cured the problem. The sensors are held in place by a screw that goes thru the aluminum ring, and has a nut on both sides, the outside nut being held by epoxy. To adjust, this epoxy must be removed. To do this, I used a triangle needle file ground to a chisel edge on the front. This will keep you from gouging the aluminum ring. The wrench needed to fit the nut is a 3/16, what worked well for me is a thin tweezers to adjust the inner nut.On the sensor base there is a casting boss that will let the sensor out only so far.Checking an old sensor base in the shop that had this problem, there was over .020 clearance as it came from the manufacture. After adjusting, the epoxy lock over the nut must be replaced. Any fast drying epoxy will work for this. I hope this information may help, as I have not seen it mentioned.
