Hi, I just got finished rebuilding me 3.8 in my 2010 JKU. This is my first attempt at rebuilding a engine. The rebuild went pretty well with no issues. I guess this started with the break in procedure. It seemed like everybody online had their own opinion. Here's what I did. I installed the engine with no spark plugs because I was told that it was safest to crank the engine without the plugs, so it reduced the pressure on the components. So, when I went to crank the motor over, it spins freely but it wont build any oil pressure. When I had the engine apart, I replaced the oil pump along with the pressure relief valve( I used a melling pump). Before I replaced the oil pump cover, I filled it with assembly lube to prime the pump. Then I made sure that the pump was aligned with the crank and everything fit well. It seems like the pump isn't working because the oil filter is still dry. I am stuck as I have no idea where to go from here. Any help or suggestions would be appreciated..

 

@WEIMWGN I had the same issue, and I also primed the engine before installing by flowing oil into it while upside down.

Two choices.
on the passenger side of the front cover, there is a pressure sensor port.
1/4in NPT thread size on my 07

Use something to force oil in there to prime the engine.

Or do what I did, I looked for oil pressure doing the same method using a mechanical pressure gauge connected to that port.
I ended up getting the bright idea to use the hose that was already attached, and to use my oil/fluid suction tool in order to suck oil up from the pan,
the gauge tool uses standard air connection connectors, so I just made a little adapter hose from one i had laying around.

I let it run until I started seeing oil flowing up the suction tool line.
then reconnected the gauge and gave it a good crank and I saw oil pressure!

 

I'll also note one thing on the 3.8.
The oil drain plug is a dumb design.
there is a big nut on the back of it, meaning there is a good 1/4+ of oil that never drains.

I assembled my engine planning to swap the lower pan for a fresh one later, I never questioned it but I kept seeing metal in the filter well past where it should start really slowing down.
(I also installed some SMCO (high temp) magnets in that pan that I planned to clean and reinstall after break-in)

When I finally swapped the pan for a fresh one, I noticed the layer of break-in material that was just settled to the bottom.
Knowing that now, I would strongly suggest using a suction tool of some sort to remove as much of that material from the bottom of that pan, especially during your break-in.

I have this one, and i keep finding new uses for it.
Amazon.com: OEMTOOLS 24937 6 Quarts (1.5 Gallon) Pneumatic and Manual Fluid Extractor, Manual and Pneumatic Oil Extractor, Fluid Vacuum Extractor, Vacuum Evacuator : Everything Else
Big seller for me, I like that brand, and It can use the pump handle or an air connection.
I just use the air connection myself.

 

Did you ever get it figured out?

 

Has anyone figured this out? I just tried the suction method, didn't work. The used a fluid pump to push oil in until I could not add any more, it blew the hose off the pump and now I have and oil mess to clean. I thought maybe my oil pressure test guage was maybe not working so I took the guage off and cranked it figuring I already made a mess so what's the worst that could happen. Cranked it 4 more times and still no oil pressure. Nothing coming out of the tube. I replaced the oil pump when rebuilding but not the relief valve since it was metal and only a year old. I am lost. I need help from all your wisdom.

 

I had a mechanical oil pressure gauge connected to the oil filter housing.
there is a sensor there to tell the computer to turn on/off the oil pressure light (aka minivan gauges).

I did some cranking with the oil pan filled with 5qts of oil with the coil disconnected.
Plan was to confirm there was some oil pressure before I let it fire up.

Nothing happened so I got the bright idea to connect my oil extractor tool to it, making a crude adapter to the air hose fittings the mechanical gauge uses.

I let it suck for a few minutes until oil started coming up into the suction tool.
Afterwards I reconnected the mechanical gauge and cranked to confirm I had oil pressure and proceeded to crank in order to ensure I had oil up in the pushrods, cam bearings, etc.
(I also do this with all 6 plugs removed, that allows the engine to crank at a slightly higher RPM)

I let it fire up and confirmed good oil pressure and proceeded with the engine break-in.

if this isn't working for you, maybe you need more suction?
It will take a few minutes for it to apply suction through the oil pump and to start pulling oil up the feed tube in the oil pan.
I used air pressure to create the vacuum, regulator cranked up to 115psi.
Make sure the tool has all ports closed, there is a vent port that needs to be closed in order for it to create suction, maybe test on some oil in the bottle first?

the other method is the way you pre-lube a LS engine.
Remove one of the oil gally threaded plugs and screw in an adapter, then pump oil in there to pre-lube the engine.
You mainly need to get oil into the pump in order for it to kick start it, best if you can lube the entire system before it starts.
Those oil gally threaded plugs are on the driver side of the engine.

I think it's under or really close to the engine mount, it's the location where the minivans mount their oil filters.
that would give you direct access to the oil gally that feeds the camshaft and crank bearings.

I also had a cam bearing that went in really tight in the front.
I worked it the best I could until I felt safe, but knowing it still needed to wear in.

the 3.8 isn't built to make it easy to drive those suckers in there with a self-aligning tool, a silly design imo.
I needed to ensure oil was flowing before I was willing to let it fire up, otherwise I was asking for the bearing to friction weld itself to the cam.



In theory you can also back fill oil into the pressure gauge port in the filter housing.
Luckily, I didn't need to, the suction tool worked great.

if you tried all things and the tool isn't working, are you sure you installed the oil pickup tube?
New seal, and torqued the retaining bolt?

Another way to feed the oil system would be to take off the rocker covers.
the oil feed for the rockers comes through the middle of the head, under the rocker support tube/shaft.
Oil feeds straight through the block coming from into the oil galleys sitting under the camshaft, then up through the heads.
one on each side.
that feeds the tube and fills it up, then feeds oil to the rockers.
The push rods also feed oil from the lifters, but it's a dead end on the rockers themselves.

a weird setup IMO, but I'm used to working on small block chevy where oil feeds up through the push rods only, then oil squirts around from ports in the rockers.

In theory you could also remove the rocker tube, then feed oil down the little hole, but I can't imagine that would be required.

With the valve covers off, cranking with the spark plugs out.
it should have enough rpm to pump oil after being primed.
With valve covers off you should start to see oil flowing, and dripping from the pushrods.
if you see that, maybe the gauge is bad and you really do have oil pressure.

If it's not sucking oil from the pan but you were able to suck oil up through the factory gauge port, then something has to be wrong.

 

Also, the relief valve, that should have come with your kit?
It's OEM or Melling.
I know Melling sells it complete, Melling is probably the OEM for it.

Maybe your relief is stuck?
if all else fails, take it apart and detail the fk out of it.

you should also be taking measurements using a straight edge, since the pump housing is part of the front cover on the 3.8.
if it's worn then it's machining and Mellings oversized pump.
Or new housing for $$$$.

 

Thanks for all this. I was away for a couple of weeks but plan go get back to this soon. I changed the relief valve after writing this, still nothing. I am going to try to fill the oil gallies as mentioned above and crank it. Just have to find some time. My suction tool is a hand pump so I am sure it could not build enough pressure. I also read somewhere that filling the oil pump with vasoline before assembly has worked for some. I am not sure if doing this will hurt or clog anything.
I did measure the oil pump housing (timing cover) when I had it apart and it was all in spec. Lost on this one.

 

For me, my engine i really had to deep clean the thing.
so everything came apart.
i even tried to pull the lifters apart, mostly to see how bad it was.
however they were seized pretty badly.

I also had to pull all of the gally plugs and ran a rifle brush through them several times.
Degreaser, and garden hose, followed up with air and wd40... lol

The rocker shafts were also a bit filled with bearing material, those fit in my ultrasonic and took several hours to clean enough where i felt good about it.
i couldn't find the plugs, so i did the cleaning the hard way.

I don't Know what state your engine was, but if you did have some bearing failure then that pressure relief could be stuck.
mine required a little motivation to get the plunger removed.
one little speck left in the system could cause issues.
Especially when your dealing with tight clearances.

 

Thanks for all the advice. I still have not had a chance to play with it. My engine was a purchased rebuild. I plan on getting the pneumatic vacuum tool to get more suction. A good friend of mine is a mechanic and he said to force oil onto the pressure switch port with a fluid pump and try starting it. I am a little timid about that method but I might also try forcing oil into the pressure sensor port while cranking with fuel off and plugs out to see if the pumping into the oil pump while spinning primes it. Just an idea.