Testing of oil gauge

[BigTallKen]

I'm looking for a way to test the operation of my oil pressure gauge.

My temperature gauge works, but my oil pressure does not. I know I have pressure, as I've checked flow to the top of the engine.

My truck was originally a I-6 truck, but I've transplanted a complete drive train from a v8 truck.

I've tracked the wire down that looks like it belongs on the oil sender, as it has the long round plug on the wire that matches the long electrode on the sender.

My question is can I test the gauge operation by either grounding the wire, or by adding current? Its my understanding that these senders operate by modulating the resistance to the ground, therefore full ground would make the gauge read high correct?

 

[Eric VanBuren]

You don't want to ground the wire to test the gauge, that can fry either the gauge or the cvr. The proper procedure is to get a 1/2watt or larger 10 ohm resistor and connect one side of it to ground and the other to the sender wire. If it is the op sender wire it should be marked 35 near the terminal. With the sender wire connected to ground through a 10 ohm resistor the gauge should read at the top line +/- 1 needle width, to be within factory specs. If that makes the gauge read you can further test it's calibration by making a chain of resistors that total 73 ohms, that should cause the gauge to read at the bottom line +/- 1 needle width. If the 10 ohm resistor makes the gauge read, but not to the "h" line, the problem May be that there is excess resistance in the connections in the circuit. The most common culprit is the cheap stamped steel nuts that attach the gauge to the circuit board, I replace them with 10-32 brass nuts. Of course a bad connection or iffy wire anywhere in the circuit can also be the cause of a low or non reading gauge.