I suspect your gap is too big. Do you have magnets or bolt heads as sensors? If magnets, are they the same polarity? Can you detect any damage to the cable, especially where it enters the sensor? Is the plug firmly engaged in the speedo?
Yes gap was too big, spoke to man at ETB and the early sender requires the gap the thickness of a 2P piece I had adjusted the gap to that shown on the back of the paper but that is for another sender apparently. Reset but now we are back to square one where over sixty the speedo flutters wildly showing 140 MPH at one point. ???