1989 Oil Pressure Gauge

[GarageHawk]

The oil pressure gauge in the '89 I bought last spring reads about mid-scale with the ignition off and about 60psi with the engine running. I thought there was a problem with the gauge but now I've seen photos of other Avanti instrument panels that look like the oil pressure gauge is at mid-scale with the tach at zero RPM.

I'd be very interested to know if other Avanti oil pressure gauges read mid-scale with the ignition off or is it supposed to drop to zero.

Anyone?

Thanks,

Bill

[wdaly]

Well, you caused me to go out and look at my '88 (305 w Stewart Warner gauges) Oil Gauge and I was surprised to find the needle at just below 30 (I thought it would be at 0)! Normal operating position is 40 and it can go down to 14 when at operating temp and idling. Almost seems like your gauge needle is simply misadjusted by about 32 psi - but if it reads correctly when running I would think that is OK. Without going to the trouble of reading my official GM manual I could imagine that the oil pressure gauge stops and stays at where it was last just before shutting the engine off (for some reason) btw my gauge will go above 40 if engine is cold and I drive fast..

Bill D

[GarageHawk]

I sent the gauge to a gauge restoration company to have it checked out.  Turns out there was nothing wrong with the gauge, it was the sending unit which had been replaced by a previous owned.  The correct sending unit for the Stewart Warner oil pressure gauge is the Stewart Warner part number 279D, (0-60psi, 90 degree sweep, 240 ohms resistance) available here  https://www.summitracing.com/parts/sww-279d/overview/

The gauge restoration company told me that this particular gauge does not use a spring that returns the needle to 0.  So when the power is off, the needle will remain in some random position.  However, the needle should go to 0 with the ignition on, but engine not running.

The gauge works perfectly with the new sending unit.  The 23,000 mile engine reads ~20psi at idle and over 40psi at higher rpm when cold.  The lesson learned is that the Stewart Warner gauge requires a special Stewart Warner sending unit to function properly.