CenturyUltra

When I turn the key on but do not start engine the oil pressure gauge pins. If I pull wire off sender and ground to engine it goes to zero. The sender on my motor has no continuity. I thought the sensor was bad. I had another used one same thing no continuity from end to end. I bought a brand new one today same thing no continuity and gauge does the same. Shouldn't the sender have continuity from one end to the other to make the gauge go to zero when not running but key on? Its an 88 242ls. Thanks.