Engine 0 oil pressure after warm up

[JohnKcj5]

I suddenly got this problem where at cold start the oil pressure is around 40psi. As the engine warms up, the pressure drops. Finally to zero. But the engine(AMC 304 ) still purrs like the day I had the rebuilt unit installed. The engine has ~7k miles on it. Tried two new different brand mechanical pressure gages, same result. Installed a new bosch filter and 10w30 oil as I've always run and noticed the oil smelled heavily like fuel. Installed a new mechanical fuel pump, oil and filter again. No change. I'm thinking the rod/cam bearings were ruined. What do you guys think? Anyone dealt with this scenario? Anything else that would cause this?

 

[NP435]

Oil smelly heavy of gas means rich and going past the rings. And its possible the bearings are toast as could be the oil pressure sender. I run 15-40 oil and 60lbs start up 25 at idle hot 45lbs at 45 mph and up hot. I have 9K on my reman AMC 258 i6 / 4.2l . Looks like you and I have about the same set ups in our jeeps. Are those
Pro Comps noisy?. Mine are Maxis RZR 33x10.5.

 

[JohnKcj5]

Well, mechanical fuel pumps are notorious for leaking fuel into the block. But even after changing oil, as soon as it warmed up the oil pressure went to zero. Pulled the dipstick and there's no smell of fuel. There is no 'sending unit' on my jeep. It's just a brass plug with a nipple for the gauge tube.

Yes, my Pro Comp MTs are noisy! But so are my fender well headers with the exhaust under my feet. HA!

 

[Patrick]

Oil tolerances could be the problem. A high volume oil pump could be the fix, assuming you don’t have smoke coming out the tailpipe and excessive oil consumption. You will still have low oil pressure with a high volume pump, but nothing to worry about.

 

[JohnKcj5]

Hey, Patrick. No smoke of any kind out of the exhaust. Just smells like a typical exhaust without cats. Wondering if the pressure relief spring/valve in the oil filter tree is sticking open. Even at 0psi, it sounds like a top. Of course I cut it off when I see the pressure going down while trying to trouble shoot. The oil pressure didn't start gradually declining over time. Just one day all of the sudden no oil pressure after it warms up. Something don't add up.

 

[Patrick]

If this happened suddenly, and if you’ve confirmed zero oil pressure with alternate methods, then it’s worrysome. If anything externally accessible doesn’t fix the issue, then there is an internal malfunction. I could not guess what it is. Good luck.