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Discussion Starter · #1 ·
So we got a new addition to the family now. A 96 Orvis edition ZJ. But its having a little low oil pressure issue based on the gauges. It runs around 20psi, and some times drops right off to 0. Sometimes i get some engine ticking too on the right side. Sounds like top or mid/top end. Lifters?? I changed the Pressure sending unit already and that didnt seem to help much. It reads a little higher, but not much, and it still dropped to 0. A little while later when i started it, it was up to about 40 and stayed there, which is good. It has fresh oil in it.

So, i thought about adding Marvels Mystery Oil to it, or an engine flush additive, or maybe even Sea Foam. But I have a few mechanics tell me that is a pretty bad idea. They say i might end up finding out more about that motor than I wanted to know. I was thinkin the oil pan is gummed up and the oil pump is getting enough good oil. It probably gummed up a lifter in the process once in a while, thats why my ticking comes and goes.

Any suggestions???

Help!!!
 

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You're saying you DID replace the oil pressure sensor by the distributor?
 

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Discussion Starter · #4 ·
AndyZJ said:
You're saying you DID replace the oil pressure sensor by the distributor?
Yes, brand new one done this morning.


technohead said:
Here is the way I would call it:

Oil pressure drops to zero + no engine noise = bad sending unit

Oil pressure drops to zero + engine noise = time for new engine
Well its not a bad sending unit, i just replaced it. And the pressure drops to zero does not always have a noise. I wouldnt think its time for a new engine, this one feels really tight. Maybe a new oil pump?? Or drop in a few lifters?? I am wondering if I can flush it out well enough to get the pump to get good oil again.
 

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Yea, the next thing I would do is drop the pan and make sure the pan is not just filled with crap and gunking up the pick-up tube like you said.
 

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If it was me I would replace the oil pump. They are pretty cheap and you'll know it's new. Don't bother with a "high performance" pump either. The 20 to 40 psi output of a stock replacment is perfect.

Get a new rear main seal and change it out while you have the pan off. It is very easy to do. The hardest part will be getting the oil pan back on with the seal placed correctly. ;)


A Mopar small block will tick at the valves first if it is starved for oil for whatever reason.

As a side note wheelers should avoid high flow oil pumps like the clap.
 

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Horus said:
If it was me I would replace the oil pump. They are pretty cheap and you'll know it's new. Don't bother with a "high performance" pump either. The 20 to 40 psi output of a stock replacment is perfect.

Get a new rear main seal and change it out while you have the pan off. It is very easy to do. The hardest part will be getting the oil pan back on with the seal placed correctly. ;)


A Mopar small block will tick at the valves first if it is starved for oil for whatever reason.

As a side note wheelers should avoid high flow oil pumps like the clap.
I agree with Horus!! You could have a clogged pick up screen for the pump or a bad pump(usually the relief spring in the pump sticks) . I would drop the pan and see what you find, clean it out, put in a new pump AND PICK UP SCREEN. Then see what its like, I think it will fix it, if not then you are looking at worn bearings causing too much clearance. Then its rebuild or replacement time. But the first place to go is the pump. Run 10w30 oil in it too, not 5w30. I actually run 10w30 and mine with a quart of LUcas oil additive, the lucas helps keep things lubed, increases pressure a little(especially hot) and helps keep the oil pump relief spring from sticking. Our shop stocks it, we use it in high mileage stuff and have had GREAT success with it!! Good luck!! :mrgreen: Its a NICE ORVIS by the way!!
 

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My '96 ZJ 4.0 had 140,000 miles when I purchased it last year. At idle the engine had a slight knock. The oil pressure at idle was 20 psi. At freeway speeds (2000-2300 RPM) the pressure could get up to 40-45 PSI, then drop back down to 20, then jump back up. I changed the sending unit. No change. I then installed a new Melling oil pump and screen after reading the oil pumps typically last only 150,000 miles. Because of the high mileage and the knock (which I thought might be a worn rod bearing) I installed a high volume (not high pressure) pump. Still no real improvement with the fluctuating oil pressure. Since I use the longer oil filter (Wix 51515), I put in 6-1/2 quarts of 10W-30 oil at changes. Luckily my engine does not use or leak any oil.

Horus, why do you say that wheelers should avoid high flow oil pumps? Curious.
 

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High pressure, high volume pumps tend to pump alot of oil to the top end. When you are wheeling and get off camber, oil sloshes away from the pickup for the pump. If your oil pump is pumping more oil to the top because its high volume or pressure, there is less in the pan. So when it sloshes you can actually starv the pump of oil and the motor. this can cause MAJOR damage in a very short time, especially when wheeling. That is why I agree with Horus statement. High volume/high preseeure pumps are designed for race applications where bearings are concidered normal wear items and replaced more frequently, so the focus is on keeping oil on the cam and valve train at high rpm's to prevent that from wearing. A stock pump is best for street and wheeling applications. Just my 2 cents from my experience.
 

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Low Oil Pressure 5.2

I would have to say it sounds like the screen on the pick up tube is clogged.
Had the same thing on my 5.2. It happens when the previous owners don't change oil regularly.
My thoughts would be pull the pan check out the pick up and pull the furthest rod cap off and look at the bearing wear and the first main cap too .
Check the wear patterns. Mine was past the lead tin stage and into the copper so it was a total rebuild for me. Even at that probably could have driven it with a new pick up tube for another 10,000 miles.
I replaced the oil pump with a new one being that they are inexpensive although the old one was really ok. There are specs on clearances and easy to check with a feeler gauge.
 

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Where to start..

1st. To the OP I had the same problem with a 4.0, the culprit was a dirty connection. Disconnect the sender and spray both connectors with electrical connector cleaner and let dry, then pack with di-electric grease and re-connect. If that doesn't do it follow the wires and look for a short or loose connection. To me if the pick-up was clogged it wouldn't be an intermittent problem. I would agree however that your oil pump may be worn.

2nd. I don't agree with the "don't use a high volume pump." You make it sound as if the oil isn't returning to the pan. Remember the pump pickup is ~3/8" away from the pan, the point at which you would starve the pump the vehicle would have already flipped! Also the oil doesn't stay at the head, it drains back to the pan. And it drains back as fast as its pumped up. if for some odd reason a passageway is clogged and the head is overflowing with oil the pump would kick into bypass mode. Not to mention if you have clogged passageways you need to clean them either manually or with an additive. I myself have been running a high volume pump in two vehicles off road for a while with no problems. Also there is a baffle in the pan to prevent the pump from being starved......

3rd. Lucas products SUCK. You will NEVER catch me dumping that garbage in my vehicles. All it is, is a thickener. A very shitty one at that, its 100% petroleum brightstock which is a group I base stock. Group I base stock oils are barley refined, and will leave deposits. Even dino oils use a group II base. Why do you want to thicken a perfectly fine API certified oil??? if you want to thicken it use a thicker oil. The 4.0 specs a 10w30, not sure about the 5.2, but if you are starting with a 30w and adding lucas your ending up with a 40w 50w or even a 60w depending how much you use. Not to mention you are dropping all of your additives (anti-wear detergents so forth), in you oil b/c lucas contains nothing. If you really find it necessary to thicken your oil there are better ways, check out schaffers moly treatment. Check out this site http://www.bobistheoilguy.com/images/lucas/lucas.htm

lastly why do you say not to use a 5w30??? personally I use a 0w30!
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All right, where did you get your info on Lucas oil, my uncle is a chemist for sunoco oil company and begs to differ BIG time with ALL your statements!!!!! Yes it is thick when you pore it out, that is the concistensy needed to properly disperse into the oil, but i am not here to argue opinions. As far as your statements on the oil returning, yes it does, BUT NOT UNDER PRESSURE!!!! Just gravity fed, that is why high volume/high pressure pumps are a problem SOMETIMES!! They can pump the oil to the top FASTER than it can return. I have built MANY race motors over the years, been in Hot Rod magazine with them and can tell you beyond the shadow of a doubt that this is true. If you get you r rig stuck on a hard incline, are revving it to use the winch and work it out, pumping 60 PSI and double the stock volume to the top end, it will pump the pan low enough to have it slosh away and cavitate the pump. Seen it happen!! If you don't believe me that is FINE! But when it happens don't be surprised, shocked or pissed cause you were warned. By the way if you have ever had the pan off your 4.0L you will see the baffle in it is a joke, in fact it helps to prevent the oil from reaching the pick up in an off camber situation! Check it out some time or I will post a pic. I have a 4.0L pan in my garage.
As far as weight oil, well to each his own. Lighter weight oils will get a very little better mileage, emissions and a couple horsepower(less than 10 RWHP on a dyno pull) but also does not cling to the internal engine parts like a heavier(and by heavier I mean 10w30) oil does. This causes increased wear on initial start up, especially to the cam and also decreases pressure due to being able to leak past the bearing clearances faster. If you have any external gasket leaks, well now they leak faster from the same effect.
---But this is ALL JUST MY 2 CENTS. Course it comes from 30 years as an Auto tech, working on a race team, and running a dyno for 10 years, but what do I know!
 

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i too am not trying to argure, i am stating facts. please tell me exactly what your uncle disagreed with??? b/c I know a couple chemist's, tribologist's, blenders, and motor oil enthusiasts who would agree with me.....Just who is your uncle, i may know someone who knows him.

Here is a virgin oil analysis of lucas.
Unless listed all are 'Zero'
TBN - 0.1
Visc - 615.3 sus
FashPoint - 435
Calcium - 3
Magnesium - 1
Phosphorus - 4
Zinc - 2

as you can see there isnt much to this stuff.

"Yes it is thick when you pore it out, that is the concistensy needed to properly disperse into the oil." COMPLETELY false. viscosity is not a factor in whether or not the additive disperses.

"As far as weight oil, well to each his own. Lighter weight oils will get a very little better mileage, emissions and a couple horsepower(less than 10 RWHP on a dyno pull) but also does not cling to the internal engine parts like a heavier(and by heavier I mean 10w30) oil does. This causes increased wear on initial start up, especially to the cam and also decreases pressure due to being able to leak past the bearing clearances faster. If you have any external gasket leaks, well now they leak faster from the same effect." Ok a lot more misinformation. There have been many people who have experienced significant fuel economy increase. HP increase depends on the viscosity change, obviously if you go from a 50wt to a 5wt you will see a higher increase. But no HP gain isn't significant, but where every .1 HP matters it helps. Thin oil clings just as well as thick oil, that is more due to the additive pack. When using thinner than recommended oil you really need to worry about the HTHS viscosity seeing that this is what viscosity bearing will encounter. The HTHS is affected by the base stocks, SOME 20w oils have a HIGHER HTHS viscosity than some 30w oils. Yes you read that correctly! Check out Red Line Synthetic Oils Product Data Sheets. They use a superior base stock PAO, POE blend and their Straight Weight oils could be considered a multi-grade due to the base stocks naturally high Viscosity Index. Lastly if yo have a leak FIX IT......

"But this is ALL JUST MY 2 CENTS. Course it comes from 30 years as an Auto tech, working on a race team, and running a dyno for 10 years, but what do I know!" Obviously not too much about motor oil, seeing that a 0w30, 5w30, and 10w30 are all 30w oils and have the same operating temp viscosity!!! The only difference viscosity wise is the cold flow.

I too have built motors, not as many as you claim nor do I have the years of experience and knowledge you claim. But that has nothing to do with knowledge of motor oil, I have a relative who has been building motors for 50+ years, but his knowledge of motor oil is no where near mine.

On too the oil pump, first of all High Volume and High Pressure oil pumps are two different things. Yes a High Volume pump will Increase pressure but there is no linear correlation. You may be right, and i am just speaking on my own personal experiences. Yes returning oil is gravity fed, but if the oil traveling to the head is greater than what is returning than at some point the returning oil will in theory be pressurized. If too much oil was displaced from the pan you would experience starvation on level ground! I just dont see this as the case, and I doubt melling would produce a pump if there was a danger of starvation due to "to high of a flow." Yes I have seen the oil pan, and the baffle isnt much to talk about, but i believe it to be more than enough.
 

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Well cavalier, first of all, the lucas issue is your opinion vs mine, not worth argueing over. You have your info, I have mine, thats that. As far as the melling oil pump not being made to cause a problem. If you contact them, they will explain to you that the high volume or high pressure pumps are made for RACE applications where more oil to the cam and valve train is needed to endure HIGH rpm situations. So don't take my word for it, email them. Then you can argue with them. If your uncle builds motors, ask him. Honestly to build motors, you really have to have a good understanding of oils, checmistry, and the working of all this in the particular application its being built for. Years ago it really wasn't a factor, the highest horsepower you would really see is 400-700. Now a 400 HP motor is stock factory issue, 700 is easily obtainable street trim and 1000 is not uncommon.
But HONESTLY, I stated my feelings on the subject to try and help the post make an informed decision, NOT AND I MEAN NOT to state opinions or get into a long drawn out peeing contest. If that is YOUR opinion and experience that is cool. Now he has both sides of the picture.
 

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my opinion of lucas is that it sucks, and anyone who knows anything about oil would agree..... sorry if i have offended you, as i am not trying to argue either. however opinions aside i have posted third party unbiased experiments of lucas, as well as facts that came directly from lucas' MSDS, and a virgin oil analysis of lucas. All of these prove lucas is a overpriced well marketed snake oil. There are also many VOA's of lucas added to oils with side by side comparisons of the oils straight, that prove lucas does nothing but lower additive levels and thicken the oil. If you want to learn about oils there is a excellent forum with thousands of members some retired oil co employees with inside contacts, some chemists, some tribologists, some blenders. There is a wealth of knowledge on this forum and any question your heart desires can be answered.

http://www.bobistheoilguy.com/forums/ubbthreads.php

"Honestly to build motors, you really have to have a good understanding of oils, checmistry, and the working of all this in the particular application its being built for."

If you want your motors to last it would definitely help. IMO a builder should be knowledgeable about oils, but thats very rare. It would be safe to say they know more than the average consumer, but thats not saying much. More importantly a builder should have a true understanding about viscosities!!!! and you have just proved that they don't.

Here is a good read on viscosities;
http://www.bobistheoilguy.com/aehaas/

p.s. you never said exactly what your uncle disagrees with? i have a feeling you just threw that out there to try to prove your opinion valid, when he never even read this post.
 

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Lets return to the original subject

Jeepin Dave, To get back to your original question: sounds like an oil pump issue. I'd recommend dropping the pan and checking it out. If it needs a pump, then consult the oil pump manufacturer for their recommendation on your application. They won't stear you wrong, because they are not going to want any problems from doing so. Good luck with it and let us know what you find!!

Cav man, you are just not getting it. This post is NOT about you!!!! Or your affiliates! I am not bringing up my uncle, because I no longer want to fuel your fire nor do I want to continue this arguement, like you obviously do! I sais my peace, you've said yours so lets just call it at that. I could through up research sites, quote facts and name names till the end of time. Its not going to change your opinion, I can see that. I respect your opinion and am willing to drop it, how about you?
 

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Discussion Starter · #17 ·
LOL. Thanks guys! All of ya's....

I am leaning more towards the pump though, like you guys. I put some additive in there the other day and drove it around a little while. The PSI ended up a little higher, but still had some times when it dipped to 0. But if I stopped and turned the engine off, restart it, and it comes back up for a few minutes. Once I got back to the house, bout 15 minutes later. I could get the PSI back up to at least 20 by just letting it idle. Hit the gas, and it drops.

Can i check the PSI right at the Sending Unit port in the top of the block?
 

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Yeah that is a perfect place to check it Dave.
 

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Discussion Starter · #19 ·
And what will that tell me? I am thinking it will rule out a bad ground, or bad connecter. Or bad gauge maybe.

I guess it will just confirm that there really is an oil delivery issue.
 

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Sorry if I hijacked the thread. I know its not about me, I gave my suggestion to the OP. I have no "affiliates." You didn't bring up our uncle because you got called out on your BS. I am not trying to argue with you, just simply correcting your misinformation. So people don't go out there and waste their hard earned money, and more importantly do damage to their engines. Which could happen if you use to much of this stuff and turn your motor oil into molasses. Nothing significant from one time use but over a period of time it would definitely shorten the life of your motor.

To the OP you can eliminate the possibility of a dirty connection by cleaning it, its free takes about 5 min and wont hurt anything.
 
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