i have a 94 ram 5,2 when i first start it presure is fine,as the truck starts warming up it will start droping,then wen the truck is is running at normal temp.it drops to 0 and oil light is on,i changed the oil,i took the switch out of my 3.9 didn't read it at all,,will 3.9 work in a 5.2 and is it the oil pump thx guy's

 

Go to the parts store and pick up a cheap aftermarket oil pressure gauge and verify it is indeed the stock sending unit that is malfunctioning....if it reads fine, then replace the sending unit...if it doesnt read normal, them drop the pan and clead the screen and pick up tube...and replace the oil pump...

 

the ram i am driving now is a 3.9 the oil presure gauge works fine,so i put it the 5.2,, and it didn't read at all,, are they the same ?? or should i buy 1 for that engine

 

no they may not be the same, depending on YEAR

here's what i did.
go to rockauto.com - look in category electrical switch and relay.

for 94 5.2, it calls for SMP part number PS233T or PS233.
for 01 3.9, it calls for SMP part number PS291 (fits 98-01)