One thing to add:

Don't do as I did and replace the oil pump because the gauge said that there was no oil pressure.

After doing as the OP suggested, I found that mine still had no gauge pressure, but was just as quiet (no valve clatter) as it was before the change.

It turned out to be my sending unit.

T'was a much easier "fix", but unlike the oil pump replacement, this made my gauge read correctly.

 

I wouldnt hurt to take a peek at a rod bearing or two and even plastiguage them. Larger your clearance the lower oil pressure will be at idle most noticeably. I bought an 88 that knocks a touch at startup, i droped the pan after a few wheeling trips i got .003 up to .007 on mine with new bearings. .003 is alowable over, .003 over that not so good.

 

I`m just replacing the oil pump because I`m changing the oil pan gasket & rear main seal. I`ve read that these pumps wear out around 200,000 km cause the gears get worn and leave a space between the housing causing poor pressure. There was lots of fresh oil ontop of the rocker arms when I changed that gasket so maybe know need but for a $100 tax included why chance it...

Did anyone ever have a prob taking the pickup tube off the old pump ?

 

old thread - but only one i could find with the info needed. still need more info though:

1. do i have to remove the starter or anything else? or can i just drop the pan and work it out (91 cherokee limited everything stock)
2. nobody ever answered the pickup tube question

 

2 jack stands

I did not remove my starter but I had my exhaust downpipe removed already but it looked like it would clear just need the right angle to get the pan out it takes some paitence. You will need to remove the lower front shock bolts and the steering damper ( shock ) you need a puller to remove the damper no hammering it out you will only bend stuff. I bought the 2/3 jaw gear puller from Lordco item # W87126 Crazy how tight it was on there when it finally popped out I thought it dented my oil pan so put a heavy rag between the 2 like I did.

You could always try with the starter on and if not no lost time...

The oil pump pickuptube TUFF to get off and back on the new one. You need to be real carefull not to bent the tube a vice would help alot, I put the pump on the ground and held it with my foot but I have more paitence then most. I thought about taking it to a machine shop so if your a hot head then maybe that`s your best option.

You will want to set aside a least a whole day and start as soon as the sun comes up it`s a dirty job you`ll need lots of rags.

I had the haynes manual for back up in case I missed something and I did, I had to go out and by the gear puller I thought my tierod puller and a hammer would do it but not without bending and or warping...

 

i just got a sweet deal on a 97 cherokee sport. 4.0 has 113k miles on it. drove it 30 minutes home no problem. put a plow on it an got it ready to make money an first time out i was doing a prking lot big enough to fit 16 cars an noticed oil pressure drop down to ohmost 0 an back up. so i put in nuetral an reved it a few times an it went up. so i kept plowing. next thing i know im ohmost redline overheating. so i shut it off an popped the radiator lid to relieve pressure an sure enough i was overheating. let it cool down an took it home. no idea what to do next...... any suggestions. oil pump, sending unit, flush radiator, thermostat????