good day fine sir
in most cases there is a bypass valve in the pump it bleeds off pressure when it gets high enough to overcome the strength of the spring behind the piston. saves your Pump drive from excessive wear
if this piston and spring set up gets stuck you have no oil pressure.....
you have oil presure eventually so its probably NOT this.
an oil filter can be purchased with or without a none return valve
you would use one without a none return valve if the filter is large capacity AND the oil enters and exits the top of it.
you get better oil flow for a lower pressure without a none return valve.....
and a filter in that orientation does the none return job adequatly on its own.
if the filter is on its side or dome side up you need one with a none return valve otherwise the oil just percolates back into the sump when yoiu stop the car.
and the amount that dissapears back to the sump increases as your lifter bore bearings etc wear becasue air can be drawn in.
leaving the car for weeks on end rather than drving it regularly it will take longer to pump up when you start it.
if you run hydraulic lifters and the car sits for months doing nothing expect any that are off the base circle and under valve spring pressure to bleed down. this can take HOURs or WEEKs or anywhere in between.
obviously when you start those rockers will clack and oil is flowing freely into those lifters. preasure will take a while to get up to normal. usually just longer than you think is reasonable...
starting the car at 0* will take longer to get pressure than at 25* cold oil, cold motor bit more drag even if the oil is good and its summer/winter viscosity modifier works. worse with straight SAE30 or 40 less so with multigrade
if you look at your filter if you can see what looks like a rubber flap below the ring of smaller holes in most cases that is a filter with a none return valve... and they are bit crap and they do fail. none return valve is a very grand name for a rubber washer...!
if these holes are just open and you can see nothing below you don't have one
mine has a none return valve and they are not exactly that effective. leave it two months and it takes a while to show pressure
remote filter head or a 90* adapter might get you a filter with big capcity and with the domed end pointing down. no small drain back is going to be able to lift a filters worth of oil out of it and down to the sump
Dave
