Null oil pressure after rebuild

[BNelsonAz]

Well the motor is in, and it started fine. Noticed I had no oil pressure (gauge is actually pegged to the negative), but there was no low oil pressure light. Checked all the connections, and there is plenty of oil on the topside of the engine. The gauge reads when the switch is turned on, but then goes negative immediately after starting.

Any ideas?

[vandor]

Are the gauge and light wires reversed?

[BNelsonAz]

Are the gauge and light wires reversed?

Hi Vandor,

Yeah that was my thought. Switched them, but no joy...

[azruss]

try switching the gage and idiot light wires.

[BNelsonAz]

try switching the gage and idiot light wires.

Hi Russ. Yep, I tried that to no avail.

[azruss]

seems like your gage sensor wire is going to ground and the ground wire to the gage. Do your instrument lights work. May be internal with the gage. I have some spares if you want to try a different gage. I also seem to remember there was an issue with the sender locations. As I recall the big unit needs to be on the back on the oil filter housing and the idiot light on the front. Had something to do with one port reading before the filter and one after.

[BNelsonAz]

seems like your gage sensor wire is going to ground and the ground wire to the gage. Do your instrument lights work. May be internal with the gage. I have some spares if you want to try a different gage. I also seem to remember there was an issue with the sender locations. As I recall the big unit needs to be on the back on the oil filter housing and the idiot light on the front. Had something to do with one port reading before the filter and one after.

Hi Russ,

Yep, everything else on the instrument cluster works.

I do have the big unit (pressure) on the back, and the small (idiot light) on the front. I believe this is an aftermarket plenum to go with the oil cooler that I have on the car. I grounded the lead from the pressure sensor (only one lead going to it) and it showed full deflection, which tells me the wiring and gauge are good. I think that it's likely a bad sensor.

[azruss]

the pressure sensor can get clogged. It has a very small oriface like a carb jet, that can be unscrewed and cleaned. May want to give that a try. unfortunately, i dont have a spare sensor you could try.

[sptcoupe]

Did you prime the oil pump? Disconnect the ignition, carefully take the oil filter off, put a something under the oil pump housing, and turn it over until you see oil coming out of the filter mount. Put the filter back on and start it. Pressure should be there. Just had to do this on my coupe. Hopefully you haven't run it much with no pressure and damaged the internals.

[BNelsonAz]

Russ: I'll try cleaning it out today.

Sptcoupe: Just so I understand, how does removing the filter and turning it prime the oil pump? I've run it for probably a half hour off and on without any pressure indication. I'm fairly sure I have pressure since there is lots of oil in the valves and the low oil pressure light is not lit.

[azruss]

If you are getting oil to the top of the motor, you are not starving for oil

[sptcoupe]

Sometimes an unprimed pump can't overcome the pressure of a full oil filter.

[BNelsonAz]

If you are getting oil to the top of the motor, you are not starving for oil

Sometimes an unprimed pump can't overcome the pressure of a full oil filter.

New sending unit, and problem is fixed. Thanks for all your help, guys!