2000 cherokee 4.0 4wd all stock.

so my motor was ticking. then i broke a piston skirt/ details at this post https://www.cherokeeforum.com/f2/pis...3/#post1846249

i ended up replacing all pistons, honing out all cylinders and new rod bearings (old ones fine but what the hell) got everything for a deal....

i have taken this motor apart once before now and never had a problem with oil pressure. now after putting back together, reinstalling oil pump i no longer have any oil pressure... or at least the gauge on the dash says so. the engine sounds perfectly fine and if i remove the brand new oil filter it is full of oil... also oil pump has about 5k miles on it...

does the oil pump need a gasket??? i dont remember removing one while taking the oil pump off. while reinstalling the pump it seemed to engage perfectly within its socket... what did i miss?

i did have oil pressure after the piston skirt broke off before taking motor apart.

also checked sending unit.. wireconnector seems fine.. never touched it anyway..

 

1) Before installing the oil pump, remove the cover.
2) Pack the voids between the gears and housing (and between the gears proper) with a soluble lubricant. Petroleum jelly works, but I prefer engine assembly lubricant (it's a lightweight grease that dissolved in engine oil.)
3) Reinstall the cover and gasket. Torque the screws to 70 pound-inches (if you don't have an inch-pound torque wrench, you may torque the cover screws to 6 pound-feet, which is 72 pound-inches.)
4) Remove the distributor
5) Install the pump, using a gasket is preferred. I tend to use paper gaskets without sealer, and use LocTite #242 on the screws.
6) Install the oil sump.
7) Fill the oil sump.
8) Using some variety of priming rod (it needs a drive tang to engage with the pump drive, and needs the drive end small enough to engage the chuck in your drill motor. A Small Block Chevrolet rod will work, if you drive out the roll pin in the end and remove the guide sleeve.)

Monitor your oil pressure as you drive the pump, you may use the IP gage or attach a mechanical pressure gage (which I prefer to do.)

Once you develop pressure, run the pump for either one full minute minimum, or (if you have the valve cover off) until you see oil atop the head for a minimum of fifteen consecutive seconds (this primes the engine throughout.)

If you don't prime the pump before you start the engine, you will not develop oil pressure trying to run the engine, and you'll end up wrecking parts. One minutes of constant developed pressure will distribute oil throughout the galleries, bearings, and suchlike; if you see oil atop the head you'll have already fed the bottom end and camshaft bearings before the oil gets up there.

I generally prefer to run a mechanical gage so I can watch for consistent developed pressure, and I'll run it for one to two minutes after I see pressure, and make sure the pressure holds.

 

^^ This is what you want.^^