6.0 stock.. when you first start the motor in the morning the oil pressure will rise to 40lbs then fall back almost to 5lbs, then a matter of seconds will rise to 50 lbs and stay there. it will not do this again the whole day, until the next morning. new oil pressure switch,oil change, swap ac to a wix filters still the same. have not been able to install a mechanical gauge to see it there. any ideas?

 

sounds like what mine did, i ignored it thinking it was a shitty factory gauge or something. turned out i had gunk built up on my spring and plunger. and yeah the pump failed after like a week of the pressure bobbling on start up. this may not be your problem but still just be aware...

 

yea, sounds like an oil pump change is due.

 

Is it possible there is an oil filter without the antisifon ? probably the pump though . Good luck .