As you get further into the test there are several other items that will keep the spark from happening. One is the HV wire from the coil to the dist cap. This can get corroded inside the weather boots and broken from changing the oil filter. Either by removing the wire or just twisting it out of the way. The bolt holding the rotor to the cam shaft can come out and let the rotor twist just enough to change where the spark jumps. The last thing that can keep the spark from the plug is a broken timing belt. If cranking the car sounds like the high whine of a sewing machine then the timing belt is kaput.
In most cases it's the reference sensors.
You can bypass the DME relay on the later models with a bifurcated wire harness. Check out
www.clarks-garage.com