Oil pressure reading low - sometimes

[ChrisinAZ]

My 64 Hardtop is running well - when it starts. Even in the warmth of AZ it needs 3/4 pumps of the gas pedal and a good grind to start. It's as if the fuel isn't staying in the carb/pipes. Once running it's fine.
Biggest concern is the oil pressure reading. The oil level is OK (extra pint in the sump, 10W40 plus ZDD) and half the time the oil pressure reads well in the middle of the scale. Then suddenly it will drop down to the low end of the scale - not all the way as when the ignition is off, just all the way to the left hand mark. It lifts a bit if I rev the engine. Then a bit later it will be OK again in the middle of the scale. I wonder if the pressure transmitter is U/S or a wiring fault. Anyone else had a problem like this?

 

[redbird1]

I have aftermarket gauges in my 66, and the gauge usually reads 80.
I assume that is psi.
At idle, it drops to about 40 psi, then upon acceleration, it goes back up to 80 psi.
I think for these old cars that is pretty normal.
What you really need to be concerned about is if you get no pressure reading at all.
Bob.

 

[tbird5866]

Sounds like you may have a fault in the wiring..

 

[ChrisinAZ]

Thanks for the replies, guys. Harley, I'll check that out. I am assuming the Voltage Reg is not the problem as the other gauges show no problems & read OK. Bob, thanks; where did you connect the gauge, is it electric or direct pressure and where is it mounted in the car? Sounds a good idea but I like the original look in the cabin.

 

[redbird1]

Thanks for the replies, guys. Harley, I'll check that out. I am assuming the Voltage Reg is not the problem as the other gauges show no problems & read OK. Bob, thanks; where did you connect the gauge, is it electric or direct pressure and where is it mounted in the car? Sounds a good idea but I like the original look in the cabin.

All my gauges are after market.
The oil pressure gauge is direct pressure, not electric.

Bob.

 

[64yellowbird]

Best bet is to hook up a manual gauge and check what the actual pressure is before you start to panic. Could be normal operation of the gauge with 45 years of age. Could be a sender/wiring too. Not sure if there's any adjustment on that gauge or not.
Good to see another AZ birder. I'm in Mesa.