I can't get my my tachs to function.. help!

[Steve1968LS2]

Spent yesterday trying to wire up my tachs. I have two of them (both Stewart Warner)

The first is the standard elec tach. The other one is their GUS unit (digital shift light with numerical readout). I have a white wire coming off the Speartech harness for the tach signal but I can't get a reading off either unit.

At first I thought it was a bad ground but the GUS unit lights up and seems to be in working order. The normal unit lights up also, but neither shows an RPM reading at all.

I have the GUS set at 2 ppr and the tach set for 4-cylinder.

I was told that the signal from the ECU might be too weak for some aftermarket gauges to read. A suggestion was made to me that I could boost it by tapping a 12v wire to the signal post, but run it though a 4700ohm resistor.

Thoughts?