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What are the symptoms of a pinched oil-pickup tube o-ring?
Zero oil pressure or simply very low pressure?
Would you still be able to get oil up through the rocker arm orifices, but just not enough to keep the engine properly oiled at operating speed?
I am having zero success getting oil pressure on a new crate LS3 via GM's instructions to spin the oil pump via the starter for 10 second intervals with ignition and fuel disabled. From what I gather this isn't uncommon.
However I know the pump is certainly moving oil, as I left the filter dry and not fully threaded on and after the first 10 second spin oil came right out the sides. When I check the oil pressure sensor via HP Tuners VCM Scanner, I get 0psi though while I fire the starter up. I have probably spun it 6 or 7 times with 7 of the spark plugs out. Additionally I started the motor and let it run for 7 seconds, putting my faith in the factory's assembly lube, but I got no oil pressure reading in VCM Scanner in that time so shut it off at the 7 second mark.
In the future I will simply use a pressurized reservoir threaded into the oil port on the block by the oil pump to prime the whole system, but I trusted GM's instructions this time around and so I'd rather not have to drop the motor out to get to that plug this time. Unfortunately it is VERY tight in the engine bay with the alternator right against that port, and while I can certainly wiggle the alternator out of the way, I cannot get a ratchet up in there onto that port fitting...
...so I need to figure out if maybe I'm not being patient enough with the cranking method per GM instructions, or if I have an issue, namely the dreaded o-ring pinch.
What are some the experienced LS guys thoughts on this?
Put a mechanical gauge on it and see what it reads.
What vehicle is this in?
Did you change the o-ring?
New(ish) / 4th-gen Miata
The next step was to buy a mechanical gauge....but I already have the Melling primer tank/hose kit to simply do this on the engine stand in the future, so I'm trying to think this through before buying something I won't be using in the future.
So the oil pan and pick-up tube are custom units made by Moroso. It came with a different color o-ring than the GM pan, but I cannot recall the color at this point.
The idea is to eliminate an electrical error and read it mechanically.
I agree
But having never experienced a pinched o-ring (or installing the incorrect one) I didn't know if this was what I was looking at and figured someone here could tell me what it typically looks like.
I had a similar experience on another car, but it had good pressure, just the pump was making considerable noise at startup, presumably from sucking in air, if it weren't for the noise we never would have known there was a seal issue at the pump/tube.
Update:
Mechanical gauge will be delivered tomorrow to be 1000% sure what the oil pressure really is (though I have a hard time believing the sensor would be completely failed on a brand new crate motor from Chevrolet, as possible as it may be).
Turns out I almost certainly put the RED o-ring that came with the GM oil pan's tube (PN#12628771) onto the aftermarket Moroso pickup tube that comes with the BLUE o-ring.
I know this because I remember noticing the color difference when I installed the pan months ago, but was unaware that meant a size difference, and I have the original GM pan sitting here with the blue o-ring on its tube instead of red. I probably switched them because the red one felt like it went on tighter...which it does since it has a smaller ID....ASSUMING it would seal better...unlike my oil pressure, the irony gauge is completely pegged to the max.
RED
ID = 19.63mm
thickness = 4.32mm
BLUE
ID = 21.82mm
thickness = 3.53mm
Eager to see what the mechanical gauge reads when cranking the starter tomorrow.
when i had that happen my truck ran fine and oil pressure wasnt bad but it was aerating the oil so the valvetrain was noisy. i drove it that way for a few weeks, when i finally replaced the oring everything was fine. i was hard on that motor too so im pretty sure there wasnt any damage done while the wrong oring was in there.
The OP should try hard not to spin the engine over too many times without knowing if he has sufficient oil pressure! It won't tolerate to many revolutions without damage to the bearings. In fact, if the OP absolutely knows he installed the wrong O-ring, I'd be into the pickup tube and be changing O-rings!!
The OP should try hard not to spin the engine over too many times without knowing if he has sufficient oil pressure! It won't tolerate to many revolutions without damage to the bearings. In fact, if the OP absolutely knows he installed the wrong O-ring, I'd be into the pickup tube and be changing O-rings!!
I would also cut open the filter and check for metal to be sure. I fear letting it run for 7 seconds with 0 oil pressure.
You should still see some sort of oil pressure on a mechanical gauge when turning the engine over without the fuel relay and coils connected. My first thought was either bad electronic sender or incorrect sender for the connector. Oil pressure sensors aren't the same from generation to generation.
The OP should try hard not to spin the engine over too many times without knowing if he has sufficient oil pressure! It won't tolerate to many revolutions without damage to the bearings. In fact, if the OP absolutely knows he installed the wrong O-ring, I'd be into the pickup tube and be changing O-rings!!
Trust me, this concerns me as well. Had I put in the thinner o-ring instead of the thicker, then I would not even be considering anything else. But I put in the o-ring that is less than a mm thicker and with a tighter ID, so I'm wondering why wouldn't it just smash and seal like normal unless it got pinched on the way in....but I don't know what a pinched o-ring looks like on a fresh motor during initial start up.
The reason I don't "just drop the pan and get it over with" is because that is WAY easier said than done. The front of the pan is less about 1/4" over the steering rack, and mounted using nuts/studs instead of bolts. So I can't drop the front down enough to even get the pan off, much less disconnect the tube. The best I can hope for is that I can unbolt the steering rack and pull it forward a couple of inches. If I can't get it far enough forward, then the whole drivetrain has to come out of the bottom of the car....for an o-ring. So it's worth trying to figure out what is actually happening, but you're right....I can only spin the motor so much without coming to a conclusion.
Needless to say, I won't be using oil pan studs in the future as it dramatically impacts the serviceability of the car.
I'm not sure I'm seeing a problem.
You put the oil filter on to some degree and oil PUMPED out the sides.
I've never heard on someone doing that, please explain.
When you're done explaining that please explain how oil pouring out of the sides of the filter is less proof that you have oil pressure than a computer readout on a swap vehicle.
Please also explain why it should be reading oil pressure on the scanner. What year is the engine, the pcm, and who did the wiring and initial tune?
Just maybe could a person remove the timing cover and then take the bolt out of the pick up tube. Then remove the oil pump. Then replace the o-ring. More or less like you are doing a cam swap? Just a thought.
A pinched o-ring isn't going to cause zero oil pressure.
The rule of thumb (that I disagre with) is 10 psi per 1000 rpm. So at a 600 rpm idle thats 6 psi.
My first real car when I was 16 had a 400 small block that had been sitting. I did a lot of body work to it and other stuff, I installed a mechanical Stewart Warner gauge set and when I got it running it read zero oil pressure. I had to be sure so I ran it at least 45 minutes.
Eventually ended up pulling the engine, dropping the pan, replaced the pump, never checked the bearings or anything.
Got it running with 60 psi pressure and that was it, ran it for several years. The only common part between a 1974 400 sbc and an LS engine. Rod bearings.
So let's go over that again.
Been sitting who knows how long, it damn sure didn't have break in lube on the bearings recently.
Started and ran with no oil pressure. For longer than 10 seconds for what 4 times?
Didn't have the internet telling me it was a stupid idea.
So what are your options. I guess a complete tear down since you can't turn it one more revolution and figure it out.
OR (here's a thought) run it long enough to actually build pressure.
I assembled/prepped the engine on the stand back in August. Brand new LS3 from the factory. I did not prime it then, because I trusted the GM instructions and I am not an engine builder nor an engineer to presume to know better than GM. By "assembled/prepped" I mean I changed the cam out and installed an aftermarket oil pan/pickup, a custom unit made by Moroso. I remember the o-rings being different colors and seeing a blue one on the GM pan I have sitting on the shelf, I suspected that I must have switched the o-rings because the thicker red one would have felt like it fit tighter to the tube. I don't recall the GM o-ring being red, but when I called the dealer I got the crate motor from and inquired with the motor's PN (19432414), I was told that the correct o-ring was orange (red). Confused yet? It gets better.
I just finished putting the pan back on.....when I pulled it off, what did I find?
A blue o-ring!...but NOT the same blue o-ring as what is on the GM pickup tube that came off the car, a lighter blue. It matches what Moroso sent me. So I didn't switch anything back in August. I put the correct o-ring on after all. Yep, I'm getting old. The GM tube does not have an indent for the o-ring, and neither does the Moroso tube....so I don't know what, if any, difference there is between the two o-rings blue and light blue.
So why did I not see any oil pressure in HP Tuners VCM Scanner??
Either I pinched it when installing back in August (which still doesn't mean I should have ZERO pressure but does make sense as a pinched o-ring would result in LOW pressure and low pressure on a fresh "dry" motor would obviously take longer to get to the top of the sensor than normal pressure) or there is an instrumentation issue...OR I simply was not patient enough due to my inexperience with the LS3.
So we're done here, filter is filled with oil this time, o-ring was dipped in oil, and tube installed nicely without issue. We're firing this puppy up. If I still see zero pressure. I'll trouble shoot the sensor. It is a brand new GM harness and sensors on the motor.
I have a Melling primer tank now, so this is a learning experience that I won't be repeating in the future. Good times!
Heres a thought. Install a working oil pressure gauge/sender, whatever it takes to allow you to see the oil pressure it has.
I agree, it does not have 0 psi
That was the plan, but the gauge I ordered from Amazon still had not arrived by well after lunch time and I found that I could just pull the steering rack forward enough to drop the pan off the studs, so I just went ahead and pulled it rather than sit and stare at the car driving myself crazy.
I’d bet the electric gauge is the problem like someone mentioned already. Wouldn’t run the engine until you verify oil pressure.
If you do find no oil pressure going up to the oil pressure gauge. May need to look into the barbell. Being that you have already verified oil coming from pump by unscrewing the oil filter and it was leaking oil.
A pinched o-ring isn't going to cause zero oil pressure.
The rule of thumb (that I disagre with) is 10 psi per 1000 rpm. So at a 600 rpm idle thats 6 psi.
My first real car when I was 16 had a 400 small block that had been sitting. I did a lot of body work to it and other stuff, I installed a mechanical Stewart Warner gauge set and when I got it running it read zero oil pressure. I had to be sure so I ran it at least 45 minutes.
Eventually ended up pulling the engine, dropping the pan, replaced the pump, never checked the bearings or anything.
Got it running with 60 psi pressure and that was it, ran it for several years. The only common part between a 1974 400 sbc and an LS engine. Rod bearings.
So let's go over that again.
Been sitting who knows how long, it damn sure didn't have break in lube on the bearings recently.
Started and ran with no oil pressure. For longer than 10 seconds for what 4 times?
Didn't have the internet telling me it was a stupid idea.
So what are your options. I guess a complete tear down since you can't turn it one more revolution and figure it out.
OR (here's a thought) run it long enough to actually build pressure.
You are correct if it is simply a pinched O-ring, and you still actually have a little oil pressure. However, if you truly have zero oil pressure, and you spin it four times for 10 seconds each, you'll have scrap for bearings, and perhaps a -.010" regrind, or more, for the rod and main journals. I know, it happened to me when the #5 cam bearing walked forward. I screwed around trying (hoping!) the oem gauge and sender were wrong. By the time I got a mechanical gauge on it to verify zero pressure, my bearings and crank were junk. This is where the LS engine oiling really differs from the Gen1 SBC. If the cam bearing walked on a priority main system, like the SBC, my crank would've been fine. But the LS oils the lifters and cam bearings before the mains and rods, so I ended up with junk for a lower end. My experience, and it wasn't a good one. I prefer priority main oiling, without thinking twice about it. Just dont spin the crank too many times without decent oil pressure......
04-20-2023, 03:55 PM
What are the symptoms of a pinched oil-pickup tube o-ring? 
