Toyota with a tacho problem

hi, sorry i didnt realy know what forum to put this is but hell its in a mini truck so seems to fit some what.anyways i got a new tachometer for my 82 yota and i cant get the thing to give me a signalthe lights on it light up but no signali connected the green signal wire to the (-) of the coilmy truck runs a 18RGEU with a Crane Xr700 electronic ignition do they have a tacho out on them?well mostly is there a way to test a tachometer by connecting the signal wire to a small voltage source or to an earth? (i dont know if the signal works on a earth restistance or positive currant i dont want to reverse load it)i remember one time i tested a temp guage by connecting the sender wire to a good earth.anyways thanks if u guys can helpcheersTom