Hey guys, Just got a 2002 Dodge Ram 1500 4x4 auto 5.9. (haven't had a Dodge since my 70 Chall back in 79 or 80) it has 200,000 on truck. Said had the eng done 5,000 ago.paper work says "Labor= transfer parts/grind valves/clean/pin fit/bore hone/install cam bearings/polish crank/grind cam." Parts= master kit/exh valves/heads. This is from the machine shop. 2/19/16 and then another shop (not sure if they installed eng) replaced water pump/fan clutch/thermostat/oil sending switch/etc. and then says, oil gauge is not working properly, suggest replacing oil sending switch. Said uses syn oil and has it changed every 3,000 miles.So the problem i'm having is when i come to a stop the oil pressure goes down to 0 and alarm bell ring- check gauges lite comes on. then i take off and it goes back up. Does it everytime. Is this a common thing with these trucks? I'm going to throw a gage on it . it looks like its a pain to get to the sending unit, its next to the dist. The eng sits back like a van, but without the cover inside to get to it. The only other problem is when i hit the gas quick in park there a hesitation. Thanks for any help.( Sorry it's so long, wanted to give as much info as i could the 1st time so we didnt have to go back and forth so much)

 

yep, put a gauge on it. this will confirm if the sending unit is bad or if the oil pressure is really low.
if the sending unit is ok. the problem can be either a bad oil pump or to much clearance in the bearings. At idle, the oil pump output is lower. Off idle the pump volume increases. rule of thumb for minimum pressure spec is 10psi per 1000rpm

Your options then would be replace the oil pump, new engine/engine work or the cheap man fix...run a heavier oil.