well im sure you all know that the oil pressure gauge has no numbers on it, just a safe zone. now my question is... where is that supposed to sit on the 3.9? mines sitting about a cm and a half above the safe line on the low side at idle. could that be the oil pump? also i was wondering what the truck is supposed to idle at.

 

My pressure gauge never sits in the same spot, sometimes its right in the middle, sometimes its slightly low, and sometimes its slightly high. You shouldn't worry about it too much until it goes outside that safe zone. lol, my truck also doesn't ever idle at the same speed either. While its warming up its usually between 600-700 and when its up to temp, its usually between 400-500.

While we're on topic of oil pressure, I have my own question... How fast do ya'lls gauges move when you crank the engine? Mine has always taken 5-6 seconds to get up in to the normal range. It has a new pump in it and a new pressure sending unit, but nothing has changed the speed that the needle moves.

 

ive noticed that depending on the temp outside, it takes a few seconds to get up there. i never actually timed how long tho. its not just you. also, my truck idles at 1000-1100 cold, and 600-700 warmed up. but i noticed when the vehicle speed sensor isnt working, it idles at 600-700 cold and 200-300 warmed up, but i dont know if thats just mixed signals from that sensor not working.. ive also noticed my oil pressure is never the same either, its just i noticed today that the pressure was sitting way below the normal range that it usually bounces between. im probably worrying about nothing, but then again, with this truck, i can never seem to be too sure =/

 

Next time you change the oil put in a bottle of Lucas, will give your pressure a shot in the arm, so to speak.......

 

The 3.9/5.2 allowable curb idle is 6psi minimum.
Maximum oil pressure: 30-80psi at 3,000RPM.
If you have any doubt about the oil pressure, you can connect a mechanical gauge in place of the sending unit to verify.

With that being said, my gauge usually sits a tad over half at idle and above idle. The highest I've seen it was around 3/4's at high RPM. But I haven't mechanically verified oil pressure.
My pressure gets up pretty quick. But, any more, I have an electric pre-oil pump I use prior to starting the truck to eliminate the dry starts.

 

Where did you get this and how did you install it? I might be interested in setting up my new motor with one when it comes that time.

 

I actually rigged it up myself.
But, you can buy pre-made kits. http://www.pre-luber.com/Automotive.htm
Finding a location for the pump can be a little hard. I mounted in on the front cross member (under the radiator, to the right), and had to get a little creative with the mount brackets at the time (need to fix it for real with all this down time).
Of course, at the same time, I also installed a oil filter relocation kit. Right now, the filter is located on the passenger inner fender. But, soon I'm gonna move it to where the cruise control crap is on the firewall since my cruise control no longer works (clock-spring is all messed up and I really don't feel like fixing it!)
I attached a diagram of the plumbing. Check valves are a must have.

 

Sweet thanks! I was already planning to set up the new motor with a filter relocation and run double filters going into an oil cooler, so now I have one more thing to add to the mix.

 

certain oils eliminate dry starts. some oils are very good if you run the motor often, but if it sits for a few days it will all drain away from the parts.(electric pump or an accumulator works well here) other oils are very clingy and will not completely drain away. motul uses a grape seed oil as an additive in some of their oils and it really clings to parts. my expirience with royal purple has been it sticks to parts pretty good too(i think its their synerlec additive?). had one bike motor sit for a month or so and there was still a bunch of purple drops hanging out on all the gears in the trans (motor and trans use the same oil) and up on the cams, crank ect(all above the oil level)

 

My oil pressure gauge bobs around depending on how much pressure the engines under and the speed, usualy between the lower line and the middle and for the idle speed, on my truck i found a plate on the bottom of the hood saying what the Idle RPMs are and mine said the warm up idle is 1800 and the regular idle is 720 but ive got a Carburated engine and i dont know how much of a difference that makes but see if yours has a plate under the hood