I have a 95 Nissan truck with the KA24e 4 cylinder. I can drive the truck a few weeks with no problems. If I let it sit for a few weeks I have no oil pressue when cranked. I pull the oil pump and prime it, reinstall distributor, and I got oil pressure. The first time this happened I'd crank it daily with no problems just to make sure I had oil pressure. So I let it sit for about a month. The other day I need the truck to pull a trailer and again no oil pressure. Yanked the oil pump, primed, replaced and viola - oil pressure. So whats the deal?

When's the last time you changed the oil? When you say there's no pressure, do you start it and let the oil work it's way back up to the upper part of the engine?

I changed the oil the first time I pulled the oil pump and primed it. It had about 3 miles on it until I started the truck the second time. I start the truck and the lifters tick and the oil light comes on. I let it run for about a minute but then shut it down now. The first time this happened i revved the engine a few times for about two minutes. I removed the oil filter both times and theres no oil in the filter or getting to it until I prime the oil pump. After I posted the same thing has happened so I pushed it to my shop and then blew compressed air down the oil stick tube while blocking the breather line on the valve cover while it was running. The oil light went out and the lifters stopped ticking. I've never removed an oil filter in the past 38 years that didn't have some residual oil left so I think theres got to be like a check valve type thing somewhere. I've even removed the oil pump from another identical truck I own and swapped them - same thing. I've drove the truck about every other day with no problems but if its not cranked for about a week it has no oil pressure. I guess I just need to drive it!

I would guess you have a small leak between the pickup tube and oil pump. If the pump loses prime then it will suck air instead of oil. When prime is reestablished then it will pull a small amount of air and oil.

I had a small flake of metal to get stuck in the by-pass valve of my oil pump. I had 40lbs. pressure at idle, I then changed the oil and never got oil pressure again till I torn down the engine.

I'm having similar problems with a new oil pump. Did you ever resolve this?

Yes and no! The last time it did this I took an air hose and blew pressure down the dip stick tube and with the air hose in the tube, cranked the engine. It primed the pump and I drove the truck about 50 miles. Ever since I haven't had any problems. So - since I didn't do anything I haven't tried before - I can't say it's totally resolved, but so far it works fine. Why - I don't know. So I suggest you disconnect the pvc connection to the breather - plug the crankcase - blow air down the dip stick tube and pressurize the crankcase with LOW pressure or you'll blow gaskets. Then crank the engine over a few minutes with the coil disconnected to prevent starting. Then connect the coil and start the engine. If you have oil pressure then remove the air and drive the heck out of it for about 50 miles. I think that may have been what "fixed" it. I previously drove only about 5 miles before I parked the truck again. Maybe getting it to full operating temp or breaking in the new parts or something. If it ever does this again I'm pulling the engine and getting one from the junk yard to replace it. Good luck!!!!

Thanks for the response. I started having my oil pressure issue after doing the timing chain and I ended up moving one of the rings between the front cover and the block. So when I blew into the dipstick, oil came gushing out between the front cover and the block just above the oil pump. Just finished tearing down the motor and I'm working on the gaskets again. Thanks for the return though!