87 ignition problem
 

I am getting no spark on my 87 f-150. It got new plugs, wires, coil, and distributor 2 years ago when it had a similar problem that turned out to be an ICM failure. When I test the coil tach terminal while cranking the test light is dim and unblinkinking. Further ignition system checks seem to be ok until the ICM supply voltage check which is good other than on pin 4 of the connector. This is the start circuit and when tested in key start position it reads 9 volts. That seems to indicate a wiring short, but I am looking for any other diagnostic advice before i start pulling wires apart. BTW this is my first post. Thanks Cale