Oil Pressure Gauge: 79 TA 400 4 Speed

[Jolo]

My oil pressure gauge shows 10 lbs with key off.  When I turn key on it drops to zero and stays at zero with engine running.  I just installed a new oil pump.  I repaired a frayed section of the sender wire, but that did not solve the problem.  With key on, I grounded the sensor and the gauge pinned far right.  When I disconnected the ground, and turned key off and on again, the gauge dropped to zero.  Before I pull the dash panel and run a jumper from the gauge, I thought I would ask if anyone has experienced the same condition.

Thanks

[firebirdparts]

I think the gauge itself is defective.  You should have zero showing with power on and the sender wire grounded.  It's sort of backwards, but since it's not doing anything with the engine off, then that might say the sender is also suspect.  The gauge, though, for sure, is not working at all correctly.

[Jolo]

Thanks I think the best option is to connect a cheap mechanical gauge and see what I get.

[Jolo]

Should either a mechanical or an electric oil pressure gauge show pressure while the engine is cranking prior to start?  I am deliberately not starting the car until I see oil pressure during cranking, on the gauges i have installed directly to the engine (I believe the car's in dash electric gauge is bad).  Seems I should see pressure during cranking.  I don't even see oil in the pvc line to the mechanical gauge.  I pulled the distributor and lined up my priming tool to the oil pump drive draft, primed some more, then lined up the oil pump driveshaft to the distributor at 18 degrees btdc.

[firebirdparts]

They will, but it takes a little while, say 5 seconds.  The electric gauge has to be powered during cranking (not just running).

[Savage Larry]

I would install a handheld mechanical gauge and then run your pump with the priming tool. That should give you a good idea of the kind of pressure your pump will build if you are worried.

[Jolo]

I just cranked it several times and got up to a steady (not fluctuating) 25 lbs of pressure on the mechanical gauge. Does that seem reasonable to go ahead and start the car?

[Savage Larry]

That sounds like it would be fine to me. Cranking speed is a lot lower than idle speed

[Jolo]

Finally got the car running.  New oil pump and pressure sender.  At idle I get over 60 lbs steady pressure.  Seems high at idle (775 rpm) but I guess that is good.  All good, thanks much for the support.