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So I had some blow by on one of the cylinder. Other than the blow by everything was great. So rebuild / refresh time. I pulled the motor and replaced 1 piston and all the rings, rod bearing, lifters and gaskets and put in a oil pump I had from my Lq9 truck. Well after we got the engine in I fired it up and had great oil pressure. So after the break in pulls we was crusing around making sure everything was working properly when i noticed the oil pressure drop to 40psi then eventually went to 30 PSI. So the next night I figured i would put my stock pump back in and check the normal things. Well i started to drain the oil and I noticed metal on the magnet on slur in the oil
So i proceed to removing the oil pump to find this...
So this is where i thought the metal fragments came from. Well I change the old pump and buttoned it back up. Everything worked great. Until it did the same thing. Worked great and then all of a sudden the psi started falling but this time it went all the way down and never came back up. I am gonna get it to the house and check the oil again. Any ideas? Just ti add a note there was no kind of engine noise what so ever.
I can't really tell how bad the scratches on the pump are in the pictures but every pump I've taken apart even a new ported pump with less than 10k had scratches in the body of the case. Are you replacing the o ring? how far is the pick up from the pan? It doesn't really make sense as to why two pumps are losing pressure. Are the relief valves stuck in both pumps? I'd get a mechanical gauge just to make sure your losing pressure.
Could it be that the beveled edge of the gear is facing the wrong way? The GM pumps only have a bevel on one side, so if you took the pump apart previously it matters how it goes back together.
I didnt take the stock pump apart and its doing the same thing. Except this time the oil psi went to 0. If it was a spun bearing wouldn't it make some noise and the knock sensors would hear it right??
I just dont understand how the pump would work one minute and then not the next. Something seem fishy. Unless i cut the oring on the pickup tube. DONT KNOW.. I'm still confused by the metal in the oil.
When i get home this afternoon i will check the oul and see what it looks like.
Every spun bearing I've seen beat like all hell. And I've seen mains lock a motor before when they turn but I would think you'd see copper in the oil by now if you had bearing problems and I wouldn't think swapping pumps would make the pressure come back up for a while. Take the allen bolt out of the bottom of both pumps and see if they're alot of grit and scaring in the relief valve. We had a LQ4 lose all oil pressure when that stuck. That valve is usually what fails. Its just a piston with a spring under it. The pump is just two mechanical gears that turn off the crank so unless you had chunks broke out it would have to be pumping something but if the valve is stuck the oil will just bypass. What were the main and rod clearances set at when the motor was put together?
Did you align the oil pump on the crank properly? It will work for a little while than go bad if it isn't aligned properly. What timing chain do you have? It looks like the pump is being stressed from the back side putting pressure on the pump gear. Just some guesses for you.
Did you align the oil pump on the crank properly? It will work for a little while than go bad if it isn't aligned properly. What timing chain do you have? It looks like the pump is being stressed from the back side putting pressure on the pump gear. Just some guesses for you.
Didnt know there was a way align the pump properly. That may be the cause of my issue.. I am running a ls2 timing chain. I turned the motor over by hand and it didnt seem to bind in anyway.
How do you properly align the pump? Looks like its a direct bolt in...
A few ways to do it, but they all involve using feeler gauges to make sure the pump body is centered on the crank. I used the method shown in this article:
Well its been back together. I out in another pump and everything is working great. I have put about 1000 miles or so since the rebuild. I figured i would put up a few pictures of the engine before we got it back in for the 2nd time... Long story and different thread. https://ls1tech.com/forums/generatio...me-insane.html Missed Crusin the Coast because of this... but any ways here is the picture and a quick lil video enjoy...
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Another Oil Psi Issue 
So i proceed to removing the oil pump to find this...
