I just recently bought a 99 dodge ram 1500 5.9 liter v8 and have had the oil pressure drop to 0 when I come to a stop. I replaced the oil pump and gaskets and the oil Pressure still drops to 0 at an idle. Is there any thing else that could be replaced or cleaned to help fix this. I have also replaced the oil pressure sending unit

 

Replace the sending unit again. Sure way to tell if its bad: If, while sitting at a stop, pressure drops to zero, but, if you even barely raise engine rpm, it jumps back up, that's a bad sender.

Just because its new, doesn't mean it's good. If you really want to verify that, put a mechanical gauge on it, and go for a drive.

 

I put a mechanical gauge on and when the truck idles at about 600 RPMS the oil pressure is just barely above 0 maybe 5 at the most is that to low for idle and would it help if I adjust the idle so it is closer to 800 RPMS

 

What's the oil pressure at 800 RPM and how many miles are on the engine? You can drop the oil pan and ensure that the oil pickup is clear and not gummed up. You might want to install a new high volume oil pump, as well -

 

The oil pressure is about 10 psi at 800 RPMS. The truck has 300000 miles but I was told the engine only has about 150000

 

HHmm... I would be replacing the oil pump with a high volume unit.

 

What weight oil is in it? When you replaced the pump did you thoroughly inspect the screen and pick up tube for any debris? Also see if you can look into the hole where the sender goes. There may be some debris blocking the flow to the sender.