oil pressure

got a 302 in my 1965 fast back. less than 1000 since it was rebuilt. when i start the car the oil pressure gauge reads between 40 and 50. after the engine warms up and it's at a idle the pressure drops to 0 to 5. any chance its the gauge? is it possible to go from that high of pressure to 0? how can i check the gauge to see if its working properly? thanks!  

you can use a mechanical oil pressure tester kit.. these are only 20 bucks at HF...



the oil pressure switch should measure with an OHM meter..

0 to 4 PSI    open circuit..

4 to 8 psi   25 to 35 ohms

90 psi    8.5 to 17 OHMs..


please... if you have a digital volt meter.. check the voltage drop..

engine running.. headlights on..

1. battery negative to the battery positive.. 14.1 to14.6 volts.

2. negative battery to the engine block..  0.04 volts

3. negative battery to the body..  0.02 volts

4.  engine block to the body.. 0.02 volts

please post results..  this test takes less than 2 minutes..      why.. ...    the ground circuit is half the circuit..  

there should be a ground wire from the battery negative to the engine block.. stopping at the inner fender on the way down..

there should be a ground wire from the back of the alternator to the foot of the voltage regulator mounting..

there should be a ground strap from the back of the engine to the fire wall..

the gauges are grounded via a wire to the inside of the firewall..  

who tightened the oil pump to the block????

who tightened the oil pump pickup to the pump..??


how much oil is in the pan.. as measured on the dip stick after the engine has sat for 5 minutes.. and how much after it had been run and just shut off???   drain back issues???

when you first put the 5 quarts in the motor and the filter..   did you check the oil level on the dip stick??

you can scrounge later model fords and grab the oil pressure switch extension ..  some are drilled for multiple taps... so you could put a small gauge into it also..  

thanks for the help! First the oil pump and pick up were installed by the builder. I check the oil before each ride and it always shows full. I will run it, shut it down check it to see back drain issues as you point out. I do not have a digital volt meter but have no electrical issues. I also plan to pick up the gauge you showed from hf. I'll let you know what the results are. Thanks again!  

I'd try a new sending unit first. I had one doing the same years ago and thought,"Oh no!", but it was just a faulty sender.  

thanks for all the replies, i have confirmed it was the sending unit. thanks!