Hi all. I'm replacing the rear main seal on my 1992 laredo, and was told I should do the oil pump as well. Do I need to replace the entire pump and screen? Is it am easy job to do? Can I just install it and it's ready to go or do I need to prime it or something? I read that somewhere but dont understand it as there is no clear explination. If anyone has a write up on how to replace the oil pump that would be great, as well as recommendations as to which pump I should buy

 

The main issue is the oil pan...it will not come out of the way until you disconnect the front shocks and then lift the frame until you can remove the pan.. the pump should be a stock melling. Do not get the Melling HV ...it will not fit without pan modification. The oil pump is 2 bolts but you have to buy the pickup screen separate and then press them together...If your not super mechanical then you might want a machine shop to put it together for you...before you install your pump/pickup assy...pour oil down the tube and spin shaft by hand until youn feell oil pressure resistance.. but then its two bolts to install ...to do the seal its best to loosen all the bearing caps...you will need a 1/2 drive torque wrench to put them all back correctly and buy the Felpro oil pan gasket...makes life easy...its the blue one with the holders...Its best to prime and to do it right you need to buy an old distributor on ebay...knock off the gear and use a drill to prime...If you cant do that then pull all your plugs and crank the engine for 10-30 seconds when all done to prime everything...you should see oil pressure on your gauge...once you have oil pressure for 15 sec then put plugs back in and start it up...buy the seal and pump assy from advance auto and make sure you input the correct year...you will get the correct parts...its an all day project...maybe 2 if your new at it

 

thanks for that. I still dont get what you mean by prime. Will the oil pump come with directions on how to do that specifically? Why are people talking about vaseline in other posts

 

It's a gear pump and is mounted above the oil in the pan requiring suction to pull oil up. If it's full of oil it will suck. if it's dry, it won't. Vaseline forms a good seal and will pull the oil up instantly. It dissolves with heat.

I recall a 70-something Buick V6 a buddy of mine bought for a song. It had zero oil pressure, but had sat for a year without being started. The pump is mounted externally about where a fuel pump would be. We took the cover plate off, packed it full on Vaseline, and it started right up with 45 psi pressure!

 

Waste of time and $. It's not a Chevy. Oil pump failure is very uncommon in the 4.0 and the cheapo off shore built replacement pump likely isn't as good as the one that's in there.

 

You can still buy good quality Melling pumps, just not at Advance Auto.
Try Rockauto.

 

The melling HV pump is a worth your time install real simple job with pan already off. and the better oil pressure never hurts either.

 

What I did , if yours has the dizzy, was to take out the distributor and manually turn the pump from the top. But MAKE DOUBLE sure you mark the position of the oil pump from the bottom when installing it , it has to line up . Same on the top, after removing the dist. Cap mark the position of the rotor button. And be aware that it will turn about a quarter of a turn go back in. I used a regular melling , and reused my pickup after a good cleaning.

Top of the pump,

 

I thought the hv melling will not fit without modification. So I have read, something to do with the pickup tube.

 

Yep, You have to beat the crap out of the oil pan to get the HV pump to fit.

And, as far as priming the pump, disconnect your CPS and crank the engine over til you see oil pressure on the gauge. Happens quickly.

 

So no need to take out the distributor and spin the gear down in there with a makeshift tool and drill?
Also when you say CPS do you mean the Crank Positioning Sensor or Cam Positioning Sensor?

 

Nope. Put it all together, dizzy and all. Before first start, crank it over without CPS plugged in til you see it has oil pressure. Plug CPS back in and fire it off.

 

Just disconnect the Crank Positioning sensor huh.
Easy peasy huh. Thanks for that.
Been thinking about building an engine, well really my friend will handle most of the heavy lifting but I will be involved, and been trying to educate myself about pre-oiling an engine and
all the preload stuff with rocker/lifters/whatnot I have been reading about lately.

 

What preload? You just torque them down.

Everyone needs to quit comparing these wonderfully easy engines to Fords and Chevys.

 

To be frank with you not a clue. Been meaning to ask my friend about this.
Been reading these threads lately.
Most of it is here:

https://www.cherokeeforum.com/f67/3-...ng-oil-255577/