Assuming your directions are correct, the first step is (and I think it was discussed on the other post of yours) to figure out if you have the correct sender. IF you have a sender for an idiot light, the sender is an on/off switch that is preset to a certain pressure. IF you have a sender for a gauge, it is a variable resistor. USUALLY, measuring the resistance of the on/off switch results in a zero or near-zero reading. As you already said, the gauge sender should have a resistance of 20-80 ohms. Measure it either on or off the engine...doesnt matter. After installing it on the engine, measure it again from the sender terminal to the engine block.....if the circuit is open (no reading), you found your problem and it is teflon tape or similar insulating problem. If the resistance goes high, you have continuity but there is something in the path....like rust, pipe dope, etc.