It gets oil pressure problem-1990 cherokee 4.0 L str.6cyl

new prob appeared today after 45 mi trip.

very discouraged

was at light, stopped in drive. oil pressure dropped from its usual 18-20 to zero while sitting there. RPM at 350 running fine.
shifted to neutral. pressure returned to normal. RPM at 500
all the way home this continued, running fine, better than before my recent repairs. idle when stopped in drive is slightly lower and smoother than before my recent repairs.
pressure is normal (20) when driving, but less responsive to acceleration than it was yesterday, after repairs. only goes to 23 or so when accelerating, yester day it went to 30-40 when giving gas.

when sitting in drive the pressure at zero, it sometimes is jumpy, jumping up to 3-4, but mostly at zero, shift to neutral and rpm increases amd pressure goes 18-20, normal.

could this be my pressure gauge?
oil pump itself?
oil screen clogged?

yesterday I repaired the ccv vacuum prob and other probs, could these vacuum repairs have broken crap loose and this just be a minor gauge or screen prob?

my book does not even describe pressure gauge or location, do you know of better manual than Haynes?

thanks, wes

Sounds like time to drop Mr. Oil Pan.

funny but not helpful

right now, not even funny :frowning:

Not meant to be funny. Changes this rapid (if real) are likely due to your oil pickup screen blanking over.

cool, I m hoping!
that was helpful!

well I m not making it up. I was wondering if the gauge might have went bad but my book tell me nothing about gauge. it says screen may be clogged but doesn t describe screen.

i m used to mechanical oil pump in my truck, no idea if this is the same type, my book is not good. i did not think mechanical pump could fail.

its our only safe vehicle and i don t have the option of hiring a mechanic, and i m unfamiliar with it, so sorry if i m a bit uptight right now

Blanking the inlet screen has nothing to do with the pump failing internally. It causes suction flow to be lost. This happened on my 1976 Fiat and my Dad’s 1963 Dodge. Both times the pickup screen was 75% blocked. Mine with paint that flaked off the inside of the pan, and the Dodge with carbon crud because the oil wasn’t being changed enough.

Just for kicks and grins I would replace the oil pressure sending unit. It’s easy and inexpensive.

oil was changed about two months ago and has stayed fairly clean, but may have broken some crud loose when i poked thru the clogged grommet, in the top of rocker arm/valve cover, that my CCV vacuum tube goes into i guess that tube could have sucked some crud into crank case too, like i said, i don t really know how it works

yeah, @PvtPublic, do you know how i can locate that? my book says its listed in a certain chapter, but its not there

If I remember correct it is screwed into the engine block down near the oil pan passenger side, or near the oil filter. Sorry it’s been a while.

no prob. any help is greatly appreciated. im getting all the info i can before i get into it.
its 96 degrees right now so i m reading my manual, which is not helping much and listening to you guys in the hope i ll have some clue later today

Depending on the manual it may have a section titled Component Location or something similar. Also try the auto parts store sites some of them may have a component locator.

its a Haynes manual.

can you suggest a more detailed one?

the Haynes for my 75 ford is great, this one is not

Might try this place you have to register but I think it’s free

oh man, the oil pan removal is a major project on this thing. my truck its just bolts and gasket

Maybe this will help

thanks P.P., i know i have to change my brake pads, so i ll go out and take the wheels off now and see what i see and get some room to work.

i ll check back here for suggestions and i ll try to change that sending unit first, if i find it.

thank you!!!
that helps!