dave1123

Okay, I bow to somebody who's done to before. Mine has that CA dual cat set-up and I wasn't sure it would clear. Live and learn.

Merry Christmas!

ThreeDee

Looks like I will need to remove the starter to get the last ooch of clearance I need to remove it. However, I have a family Christmas party to go to now, and I figger that's a tiny bit more important than pulling an oil pan.

ThreeDee

Got the pan off today, though I discovered if you run it up on ramps the suspension will not give you enough clearance to drop the pan. So, I CAREFULLY jacked up one side high enough to put a jack stand under it at its highest position and remove the ramp. Once I got it down the pan practically fell out.

Dave1123, I found that the pickup screen only had a few chunks of crud on it, and not enough to significantly obstruct oil flow. I decided while I was under there to pull the oil pump. I discovered there is a wrong place to be when pulling the pump on a 4.0, and ended up with a beard and moustache full of oil. (My wife refused to kiss me. Go figure.) Somebody has pulled the pump before. Two oil pan bolts were only slightly more than finger tight, and the bolts holding the pump in were not as tight, in my opinion, as they should have been. When I took the cover plate off the pump, I noticed only the drive gear was showing the little round mark. The gears don't look that good, (though I have seen worse) and the driven gear had been reinstalled backwards, which is why I didn't see that little mark. (Is it called a timing mark? I can't remember.)

Regardless, I think I have found the culprit.

What is your opinion on high-volume pumps? Are they worth the extra $20? (I can get a stock Melling pump for $79.00 and a Melling high-volume for $97.00 here locally.) Or should I just drop $30.00 on a Melling rebuild kit and slap that puppy back in?

CrisostamoSH90

I suppose I shouldn't have assumed you everything hanging at full articulation. I apologize for that. But you got it out, it's not too bad huh? I guess it's just about how everything a settled whether the starter has to come out or not.

I personally don't have an answer for you on the oil pump, however I would assume you're a guy that likes to do things himself, so why not rebuild the pump. After all, and I may be wrong, but it doesn't matter how much oil you throw at the engine with high volume, the crank and cam bearings are what give it the pressure. But Dave might think differently, he's got a few more years under his belt than I

Nick

ThreeDee

Well, it's not that I didn't know about hanging at full articulation, I just didn't think about it. On the occasions when I need to jack up my '54 Ford F250 (which has solid axles front and back), it's usually better to leave the axle hanging.

As for the pump, after taking a look at the pump body itself, I found some scoring. Not much, but enough that I think I'd rather just get a new pump so we don't have to worry about it later. Rock Auto - one of my favorite places online to get car parts - has oil pumps at better prices than locally.

CrisostamoSH90

If I had a dollar for every time I've fought with something to remember it's easier if I do "this" I'd be a rich man! That being the case you're better off buying a new pump. Give yourself peace of mind that you weren't too focused on your beer to reinstall a small part. I'm a hoarder so I would save the old pump with the intention of rebuilding it as a back up, and then let it collect dust in the garage. Rock auto has great parts and great prices with quick shipping, you won't go wrong with that option. Best of luck to you!
Nick

ThreeDee

We have a couple of old BMW 325s. It has become a personal joke that every time I need to work on it I need to remove the air cleaner and air flow meter, because it seems every time I need to fix something on one of them, it's in the way.

And thank you for the advice you've offered. I haven't gotten a repair manual for the Jeep yet, so I'd be doing everything by feel if it wasn't for folks like you.

dave1123

Sorry, I had to get some sleep last night for my paper route, but you have a good head on you to figure out you'd be farther ahead just buying a new pump and putting it out of your mind. I guess you were right after all to pull the pan and check the pump. That's the problem with buying anything used, you don't know who has had their hands on it and what they've done.

On the high volume pump, unless you're going to run it at high revs continually, like in a boat, you don't need one. With the pump worn, you weren't getting the volume at idle to supply the lifters anyway. The PO probably flipped the outer ring to try to get it to seal better. Gerotor pumps are positive displacement, but with clearance between the rotors, there is a lot of that displacement lost. Also, you have no idea if the PO messed with the relief valve. A new pump should solve everything. This comes from Hydraulics 101.

BTW, you'll want to prime it before you put it in. Then pull the ASD relay and crank it until the oil pressure gauge jumps up. Then light it off.

ThreeDee

ASD relay?

Shall I use moly or good ol' Vaseline to prime it? (I can find the Vaseline. I don't remember where I put the moly.)

CrisostamoSH90

Auto shut down relay. It kills spark and/or fuel in the event of a rollover. It's in the fuse block in the engine compartment and labeled ASD relay. Basically it lets the engine crank, causing the pump to operate and building up pressure, but doesn't allow the engine to turn over and run dry. No lube is never a good thing! It's always a good idea on these to pull that relay, even when you just do a pan

ThreeDee

Ah, okay. With our old BMWs you remove the fuel pump relay and jump across a couple of terminals with a wire. Thanks!

CrisostamoSH90

Same idea different steps. Jeep being the off-road power houses they are planned for us rolling over our 4wd monsters. Or maybe it was for highway safety, but that's a more boring reasoning. Anywho just pull it out to be sure. Good luck!

Nick

dave1123

Actually the ASD relay has more to do than that. When the PCM detects a signal from the CPS that the crankshaft is turning, it energizes the ASD and fuel pump relay to power up the ignition and injectors, and the fuel pump. AS LONG AS THE SECURITY SYSTEM says it's okay, it will stay running. Otherwise, it will shut down within 30 seconds. IDK anything about roll-over protection except the valve in the tank filler neck. It seems to me it would be tough to have a roll-over sensor on a vehicle that sometimes takes to the air! My wife's friend's Ford Escort would shut down if she hit a pothole!

This is why the CPS is so critical. If the PCM doesn't receive a clean, continuous signal, it shuts off the engine. Pulling the ASD relay is an easy way to get it to NOT fire up.

I'd just fill it with engine oil to seal up the clearances in it and create suction. It doesn't suck air very well. On some of GM's early V6s, the pump was high on the block and if it sat for a long time, you had to take off the cover and pack it with Vasoline to get it to draw oil. The jeep pump is practically IN the oil, so it doesn't have to lift it so high. There is an anti-drainback valve in the oil filter to prevent letting the pump go dry.

ThreeDee

Well, crud. Dirty words. Etc.

I haven't done anything with the Jeep in several days, given that my daughter is short on cash and cannot currently afford the parts, and ol' Dad is a bit tight for funds right now, not to mention wet weather. However, while it's kind of cold today and the sun is shining, so I went outside to piddle around with some stuff.

When I got the pan off it was getting dark, and there was still some oil in the pan. I poured that out and then covered the pan with a sheet of plastic. Today I needed to move the pan out of my way, and that is when I noticed two hunks of aluminum laying in the bottom of the pan. I knew what I was looking at, so I grabbed a flashlight and shimmied under the Jeep. Sure enough, part of the skirt on the #6 piston is broken off.

I REALLY don't want to replace a piston with cold weather coming on!

Of course, I'll have to. It's just one more expense.

The cylinder wall looks okay, thank goodness. Any thoughts on why a piston would break at just less than 150,000 miles? I had a piston break on a VW I used to drive, but that engine had a LOT of miles on it.

dave1123

The only thing I can think off is the piston skirt length on the 4.0 is rather short from the wrist pin to the base of the piston. This allows the piston to "rattle" up the bore if the clearance gets a little loose.

As I recall, Chevy small blocks have "slipper" pistons in them where the skirt extends down quite a ways, but is cut narrow to clear the crank. This "slipper" keeps the piston straighter in the bore. It's not unusual to see the bottom section of these piston skirts scored up on a very well used engine.

This is just my brain frying, but I think I'm on to something. No drugs involved, lol. The 4.0 does occasionally eat pistons and it's always the skirt that breaks, not the crown under the rings or the wrist pin boss.