1985 dodge short bed truck slant six four speed everything works drove daily until engine lost oil pressure a week ago motor not locked up truck has been parked since anyone have any ideas

 

So have you put a guage on it to be sure you have no pressure. If not and Harbor Freight is close pick up a oil pressure test guage and see if you get a reading. If not it could be your oil pump or worst a spun main or rod bearing.

 

Do you have allot of miles on that motor? was it nockin? or making noise?
it's like what bremereric says put a test gauge on it and be sure you have no O.P.
Then check pump and other parts.

 

Check oil level and smell for gas dilution (caused by bad fuel pump.) Check oil visually for "thinness" caused by gas dilution.

Remove filter, crank engine and see if it pumps oil out

You have a shop manual, even for an older model? On those engines you can remove and inspect the pump from the outside of the engine. You may have to disconnect some things, and the mounts, and jack up the engine to do so, not familiar with that chassis You will need a new o-ring/ gasket set for the pump

 

Could be just a bad oil pressure sending unit !! stripped oil pump shaft

 

You have a bad oil pump,try to use a manual gauge and see if you get any reading off it,its not unusual for a dodge with greater mileage to loss oil pressure,i own several of them and have had to replace the oil pump in few of them already,anything over 100k and the oil pump could fall short on them best of luck with it.

 

More then just a bad oil pump will cause no pressure... I'd start with easy then go for the heard to replace items...


OP:

Use a mechanical gauge. If it checks out that you have pressure: Replace the sending unit.

If not: Youll need to do what 440roadrunner says. Listen to him.