In my sister's 94 jeep xj with a 4.0 we made the mistake of putting a Fram oil filter in it. When we were on a drive the oil pressure started getting low then completely went to 0. We pulled over and there was a knock. The noise sounds like it's coming from the top front of the engine. We got the jeep home and put on a wix filter and now the oil pressure is pegged out but the noise is still present.
so my question is what is the most likely thing to be causing the noise (lifter? timing chain?) Do you think our oil pump is actually going out and it happened to be around the time we did the fram oil filter? Is this fixable without a whole new engine?
I am new to the jeep thing and so I'm not sure what the most common problems are, any and all help is appreciated.

 

Check the oil pressure with a mechanical gauge. That's the first step. Report back with results

 

I went and picked one up at harbor freight, at idle it was reading 40. So we have oil pressure now, we also did another oil change and put marvel mystery in there but that didn't seem to help at all. The oil that came out had small metallic specs to it (if you stur the oil it has a silver color to it). I am having a hard time deciding if the noise is up high or down lower. What do you think is the most likely thing causing the noise?

 

Ah the old orange filter of death...I haven't used one for a long time because of the horror stories of the filter media/cardboard coming loose and clogging the oil passages...And with visible metal in the oil from a small amount of miles it sound like it's on self destruct mode and you'll be in there to see what it is soon enough..Don't keep running it with the knock or there probably won't be much to rebuild if that's what you plan to do...I'm guessing a bearing...

 

Check compression, if one read zero (or really low) , pull the valve cover and see if you wiped a cam lobe.

If compression is good, you may have wiped a bearing.

With the amount of metal you say you are seeing,, I'm thinking cam.
But check compression, that will tel you where to and where to Not look for the problem.

 

I ended up having a neighbor come give me his 2 cents and said he would pull the valve cover. I pulled it (didn't think to look down at the cam but can do that tomorrow) but I started the engine for a few seconds with the cover off (I know people don't suggest this) I don't think it's a rocker like I thought, it's definitely lower down my guess is a bearing spun or maybe the cam. I will shine a flashlight down at the cam tomorrow and go from there. I think we're pulling the motor and rebuilding it though.
Thanks everyone I will be sure to keep you updated