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Agent98 Reader
8/17/18 2:16 p.m.
t25torx Dork
8/17/18 2:57 p.m.

In reply to Agent98 :

Yeah I already swapped the sensor out because the first one was pegged to 80 like a bad unit does. The new one reads 0 psi. I hooked a true mechanical gauge to the port for the sensor and it also reads 0 psi at idle. So the sensor is sending the correct info to the computer now. So I ether have bad pump with worn seals, or the pumps relief valve is stuck open, or the pickup is clogged int he pan, or the filter anti-flowback valve is bad and not flowing oil through it.

wvumtnbkr UltraDork
8/17/18 3:43 p.m.

Or there is no oil in it....

t25torx Dork
8/17/18 6:04 p.m.

Oh there oil in it, a fresh 8 quarts of the finest 5w30 money can buy. Level is spot on at the dipstick.

759NRNG SuperDork
8/17/18 8:25 p.m.

Sorry I know nuttin' bout this oil pressure issue, but the amount of effort you have put forth on this is a major FIST BUMP BRO!!!.....especially your removing the third member in this....BIG UPS!!!  

Scottah Dork
8/18/18 2:21 p.m.

Maybe the oil pickup tube o ring? 

jfryjfry HalfDork
8/19/18 8:21 a.m.

Man, are you SURE it doesn’t have oil pressure????   

It just seems that with zero, you’d hear a lot more commotion like bled-down lifters and other $$ noises. 


If you do tear into it, I imagine it’s like the ls7 in that you have to drop the front cradle to be able to remove the harmonic balancer and the oil pan, or remove the steering rack (out the pass side I hear) to remove just the balancer. 

Also, I believe the balancers on that motor are known to go bad. PowerBond makes a sfi-rated replacement and race balancer that is affordable.  

You could also get timing chain guides since they’re cheap and I think they’ll be accessible

t25torx Dork
9/11/18 8:25 p.m.

Well guys with the weather getting nicer out I finally got around to pulling all the stuff out of the way to get to the crank pulley on this thing. Man is that steering rack a pain in the arse to remove. That was the longest part of the teardown. I removed the old oil pump and didn't see any signs of failure. No stuck relief valve, no burs or scratch marks on it. Also checked the old O-ring, it was not split or in bad shape.  Hmm okay, now what?

I had it apart so I went ahead and replaced the oil pump with a Melling high pressure unit. Replaced the o-ring with the one specified for the the blue ring replacement and being very careful with it. Finally got the correct balancer install tool and got it buttoned up enough to crank it over with the injectors unplugged to see if it would build pressure. Nothing.. nadda, zip, zilch. Fantastic.

I'm at a loss now. I took the front galley plug out since I could get to it now and hooked up the gauge to there, no pressure there either. I guess I need to take my gauge out of that plug next and see if oil pumps out when cranking it. If it does, then I guess the pump is working and the o-ring is sealed correctly, if not, I'll have to take the cover off again and see if I screwed it up when I installed the pump. After that, I suppose I'll have to just yank the motor and see if I have bad bearings somewhere or if the oil flow control barbell thing (you can only get to with the rear cover off) is too loose and not allowing pressure to build.

I did hook my air hose up to front galley plug and pushed some air through it to see if I could hear any leaks. I could hear oil bubbling in the pan and it was airing out through the pcv system. So I don't know. I'm frustrated now.

So anything I'm overlooking LS experts?

HotNotch New Reader
9/12/18 11:59 a.m.

Is the gauge bad?

B757Captain New Reader
9/12/18 12:46 p.m.

Possibly the pickup tube has come loose? Or a bad gasket for the pickup tube so it's sucking air, not allowing the pump to prime?


I remember years ago some Dodge motors with external oil pumps (440, etc.) were really bad about losing prime, even during oil changes. WE used to pack the pump body with white grease to get the pump to prime. I know the LS system is not like that but I can't think of anything else unless there is physical damage in the motor from the PO

t25torx Dork
9/12/18 2:35 p.m.

I poured oil into the front oil galley plug hole before attempting to prime it with the starter. I am going to get a small garden sprayer and make an oil priming pump to see if I can get the pressure up and good and primed before I try this again. I'm thinking I can pressurize with the sprayer and hook the gauge up tot he top prot and if it makes pressure then I might not have to remove the whole damn thing. But here lately that does nto seem to be my luck.

wvumtnbkr UltraDork
9/12/18 3:30 p.m.

Where is the pressure gage?  Is it possible that the passage where the gage is connected is partially / mostly clogged?


Do the pushrods have a hole in them like the old SBC?  If so, can you take a valve cover off, spin the engine on the starter and see oil come out of them?  

Im still suspicious of an engine with no oil pressure that is still managing to run without bad noises.  Is it solid lifter or hydraulic?  If hydraulic, I would think that thing would be making all sorts of clatter.


Maybe not a great test, but if run air into an oil port, does the pressure gage read the air pressure?

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