Oil Pressure gauge not reading

[Black Mountain AT]

So now that we have our M1123 running I'm finding the little issues. Oil pressure gauge on the dash cluster isn't reading.

I've checked the wiring and it appears correct. Have also checked to see that we are connected to the oil sending unit. And have checked to make sure we enough oil and it appears to flowing through the engine. What should I replace first?

 

[Mogman]

You should not replace anything until you have troubleshot the problem to the defective device.
Are you getting 24V to the gauge wire 27H?
Does the gauge move when the wire to the sending unit is open (removed from sending unit) and or shorted to ground? (wire 33A/B)

 

[Mogman]

To farther elaborate, all of the old automotive analog gauges (temp/pressure/fuel) work the same basic way, you do not need the particulars of a gauge to do some basic troubleshooting.

All analog automotive gauges act pretty much the same or the reverse of the same.

That is to say all analog automotive gauges will read one extreme way when the wire to the sending unit is open and the other extreme when the wire going to the sending unit is grounded.
It can however be one way or the other, max reading when shorted or max reading when open depending on the gauge and application.
SO, if you try it shorted and then open and you get full scale one way and min. scale the other the gauge is likely "working" although that does not guarantee accuracy.
In your case if you get full scale one way and min. scale the other you likely have a bad sending unit, if you get no deflection of the gauge when the wire going to the sending unit is shorted or open you have a bad gauge or the gauge has no power, or ground, the case of the gauge must be grounded, IIRC the HMMWV has a ground wire running to each gauge, but I am getting old so...