Can anyone out there tell me how much voltage is suppose to be coming from the wire at the oil pressure sending unit? does the gauge regulate this or is it from somewhere else? i check all the write ups i could find on line they did not help. thanks in advance.
it is a 76 cj 7 with a 84 258
The voltage at the point you describe varies and is dependant upon the oil pressure. Take a look a Jaffer's</font color=red> page that says:
Oil Pressure Sender
This sender is on the engine block and looks like a small 2 X 3 inch filter with one terminal. The other sender with the two connectors is an oil pressure switch .
It is supposed to close above 4 psi and goes to a dash warning light in some speedometer clusters and in other models it sends the signal to the engine's computer.
To be sure the problem is not the gauge, you can momentarily short the wire from the output of the Sender to ground. This should show up as 80 psi on your gauge. No resistance at all (full 12 volts). DO NOT hold it long in this position.
If the needle does not move from ZERO psi then, either the wiring (open circuit) or the gauge is bad. If it does move, the sender unit is bad.
Oil Sender Resistance
These are hard to test but might help choose the correct replacement.
*0 PSI 234-246 ohms
*20 PSI 149-157 ohms
*40 PSI 100.5-105.5 ohms
*60 PSI 65-69 ohms
*80 PSI 32.5-34.5 ohms