There are two "sending" units on Ranger engines, one in the Fuel tank.
Temp sender location depends on the engine. i.e. 2.3l, 2.9l, but usually on the upper engine near thermostat housing, 75ohms cold and 950ohms warmed up, these are "about" numbers and can vary by 10-15ohms
Oil Pressure sender is usually located near the oil filter, in an '88 this would be a switch, not really a sender but still called that
Infinite ohms(no connection) engine off, oil pressure below 5psi oil pressure
0 ohms, engine running with above 5psi oil pressure
These are "senders" so only have 1 wire connected, sensors have 2 wires
Fuel gauge sender is in the tank, on an '88 it would be 73ohm empty tank and 10ohms with full tank.
In 1989 that changed to 16ohms empty and 158ohms full, so incompatible with older gauges
Good read here on the Ford fuel tank units:
http://www.fordification.com/tech/fuel-sending-units.htm
Welcome Visitor! Please take a few seconds and 
