Low oil pressure?

[Jadaharabi]

Well this is only my opinion but I believe without the plug the oil would loop and have no resistance so it builds no pressure. With the plug in there it forces the flow path to go through the filter and then into the motor where it encounters resistance. The pressure then would equalize on both sides of the plug which may be why the plug does not blow out. Just my opinion. The book may be wrong, I just wanted to share another reference.

My 1997 service manual for the Dodge Ram trucks on page 9 - 52 for the 3.9, page 9 - 74 the 5.2, and page 9 - 117 for the 5.9 all say you will have low erratic or no oil pressure if that plug is not in the back of the block. Why would Chrysler say that three times in the service manual?

 

[brian6pac]

All I can say is look at the schematic and show me were the oil goes.

 

[brian6pac]

By the way It was printed wrong and everyone copied it.

 

[Duane]

All I can say is look at the schematic and show me were the oil goes.

In to the filter, out of the filter, down towards the pump flow and back into the filter again and keeps repeating. IMHO until you steer it towards the engine galley.

 

[RustyRatRod]

Has the oil pressure been verified low?

You know, as in post #104.

 

[Jadaharabi]

All I can say is look at the schematic and show me were the oil goes.

.
Without that plug in the oil pressure goes up and the oil starts looping around the passages in the back of the block oil pressure drops and then maybe it'll pump up again until it bypasses in the meantime the oil can Loop in the back of the block.
Chrysler has been saying this since the early 60s right on up until they discontinue the LA Motors.

 

[brian6pac]

The oil gets sucked up the pick up into the pump, and out of the pump through the engine and comes out the bearings, rocker arms and around the lifters and that's pretty much it. If the plug is in it goes through the filter and out to the galley's, and goes out the bearing's, if the plug is out the filter just fills with oil and the oil goes to the galley's and goes out the bearing's. Are you getting the picture! If you don't understand hydraulics you wont understand.

 

[Jadaharabi]

The oil gets sucked up the pick up into the pump, and out of the pump through the engine and comes out the bearings, rocker arms and around the lifters and that's pretty much it. If the plug is in it goes through the filter and out to the galley's, and goes out the bearing's, if the plug is out the filter just fills with oil and the oil goes to the galley's and goes out the bearing's. Are you getting the picture! If you don't understand hydraulics you wont understand.

.
I think I understand the Hydraulics pretty damn good myself.

 

[brian6pac]

.
Without that plug in the oil pressure goes up and the oil starts looping around the passages in the back of the block oil pressure drops and then maybe it'll pump up again until it bypasses in the meantime the oil can Loop in the back of the block.
Chrysler has been saying this since the early 60s right on up until they discontinue the LA Motors.

So you are saying the the pump is pumping oil and it cant go down the galley that is wide open because it's stuck in a loop

 

[Jadaharabi]

So you are saying the the pump is pumping oil and it cant go down the galley that is wide open because it's stuck in a loop

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That is not what I said so don't be putting words in my mouth.

How many motors do you put together without that plug in it?

 

[brian6pac]

.
That is not what I said so don't be putting words in my mouth.

How many motors do you put together without that plug in it?

NONE, BUT I KNOW THE OIL GALLEY'S AND YOU ARE DEAD WRONG, SO

HERE IS YOUR CHALLENGE IF YOU WISH TO ACCEPT, SHOW ME THE

GALLEYS AND PROVE ME WRONG. SHOW ME WHAT YOU ARE TALKING

ABOUT.

 

[Duane]

The oil gets sucked up the pick up into the pump, and out of the pump through the engine and comes out the bearings, rocker arms and around the lifters and that's pretty much it. If the plug is in it goes through the filter and out to the galley's, and goes out the bearing's, if the plug is out the filter just fills with oil and the oil goes to the galley's and goes out the bearing's. Are you getting the picture! If you don't understand hydraulics you wont understand.

I understand hydraulics pretty well.
If you take a look at the schematic you posted, you are assuming that when the oil leaves the filter that it will go upward against gravity to the main oil galley. Why should it go up. Why not go down. The plug is not there, it is free to go down. That is the dual purpose of the plug, to steer the direction of flow. Without the plug there is an optional flow path that is not necessarily toward the main galley.
This optional flow path has very large diameter passages so the oil can just free flow around in a loop with little if any pressure.
Oil pumps will not make pressure until there is a restriction.

 

[Inertia]

In to the filter, out of the filter, (somehow gains pressure) down AGAINST the pump flow and back into the filter again and keeps repeating. IMHO until you steer it towards the engine galley.

 

[brian6pac]

OOOHH, Damn I forgot about gravity WTF Duane, Take out your oil sending unit and look down the hole and start the engine and tell me what happens.

 

[Jadaharabi]

NONE, BUT I KNOW THE OIL GALLEY'S AND YOU ARE DEAD WRONG, SO

HERE IS YOUR CHALLENGE IF YOU WISH TO ACCEPT, SHOW ME THE

GALLEYS AND PROVE ME WRONG. SHOW ME WHAT YOU ARE TALKING

ABOUT.

What are you yelling for?
I see that you always put that plug in. That pretty much tells me that you believe it should be there.

I guess you understand that within a column of oil that the oil has columns within the column that is going back and forth instead of all just spurting out forward.
All I'm going to say is you're better off putting the plug in there than running without it or Chrysler would not have told you that for 50 years.

 

[Duane]

OOOHH, Damn I forgot about gravity WTF Duane, Take out your oil sending unit and look down the hole and start the engine and tell me what happens.

Someone once explained to me that electricity and hydraulics are very similar. When flowing they always try to take the easiest path.
Your schematic is upside down from a real engine. The oil has to flow upwards to get to the main galley. You are assuming it will make a sharp right had Turn upwards when it could make a left turn downwards without the plug. It could flow a combination multiple directions all at one hence the terms low or erratic pressure. It could go through the filter backwards even.
I know those passages too. I drilled all mine larger on my new build.
You can disagree with me if you want but you know that plug needs to be in there. I've offered you a possible explanation and you don,t agree. That's ok.

 

[Jadaharabi]

Someone once explained to me that electricity and hydraulics are very similar. When flowing they always try to take the easiest path.
Your schematic is upside down from a real engine. The oil has to flow upwards to get to the main galley. You are assuming it will make a sharp right had Turn upwards when it could make a left turn downwards without the plug. It could flow a combination multiple directions all at one hence the terms low or erratic pressure. It could go through the filter backwards even.
I know those passages too. I drilled all mine larger on my new build.
You can disagree with me if you want but you know that plug needs to be in there. I've offered you a possible explanation and you don,t agree. That's ok.

.
Reminds me of a quote that Pappy Towner used to say.
People are like water they'll seek their own level.
I too was told that electricity and water are alike in that they will both seek the path of least resistance.

 

[Jadaharabi]

Sorry Cope for going off on a tangent. Was not my intent to steal your thread.
I do have another question for you though.
If your dipstick is properly calibrated and you're running on the full mark. And all the plugs are in the system where their supposed to be, and your oil pressure gauge is working correctly. I would consider using a baffle in the oil pan.
This is assuming that internally everything is assembled correctly.

Are you running a windage tray?

 

[Duane]

My new engine is having an oil pressure issue.

At idle I make 25psi hot, 50PSI at 1000 rpm and 65+ above 2000 rpm.

I've been doing some freeway testing and after 15 min at around 2,500-2,000 RPM I got off the free way and oil pressure dropped to almost zero. We're not talking hard on the breaks or down hill just sitting at the light. I put my foot in it to bump it up back to 25 so it was not idling at zero. Twice now I've seen it do this.

HV pump running 20-50 Joe Gibbs oil.
Factory car pan.

Maybe 200 miles on a full build.
Balance, blueprint the whole nine yards.

I'm on my second oil change, I drained it at about 100 miles and cut the filter just to make sure all was well. No metal in the filter.

11.5-1 comp ratio.
Big lumpy cam (dont have the specs on hand)

Any ideas, I'd hate to pull the engine again but I also dont want to ruin my new engine...

Engine was built at a very good, high performance machine shop.

Is your engine idling at the correct rpm. I know I thought my Cummings engine had low pressure until I adjusted the idle to factory specs and the oil pressure went up with it to something reasonable. Just a thought.

 

[T56MaxTorq]

Without the plug, the filter assembly just becomes a lazy accumulator. At this time, any oil flow through the filter is dependent on the differential pressure of the filter media.

In the book, they’re illustrating the incorrect plug. For their warning of “erratic or no oil pressure,” the missing plug must return oil to the suction side - the pan. Not a normal oil system without filtration.

 

[Inertia]

There are none so blind, as those that refuse to see.

 

[nm9stheham]

Well this is only my opinion but I believe without the plug the oil would loop and have no resistance so it builds no pressure. With the plug in there it forces the flow path to go through the filter and then into the motor where it encounters resistance. The pressure then would equalize on both sides of the plug which may be why the plug does not blow out. Just my opinion. The book may be wrong, I just wanted to share another reference.

I really cannot explain why that statement is there in that book. It really does not make sense, once the pump is runinng and all air is purged. BUT, if the plug is missing, then the anti-drainback feature of these filters, will be mostly defeated; oil can all drain back out through the pump and pickup and leave them 'dry'. I suspect there will be a delay in pressure build up at start-up in this case, and that may be the real issue that the FSM contributors were trying to address. Chrysler has used anti-drainback filters in all sorts of engines for a long time.

The filtered path and the direct passage (that normally gets plugged) are 2 parallel paths into the main oil gallery. The oil will not flow in a circle for these 2 simple reasons:

• Even with large passages, ANY flow will create a pressure drop in the passages; so pressure will be lower at the top, where these 2 paths rejoin; it may be just a fraction of a psi lower, but it WILL be lower. To say that oil will flow backwards through either passage means that the oil has to flow from that lower pressure point back to a higher pressure point (the pump output). For those who understand hydraulics, look at it in terms of where the pressures are higher or lower, and it will make sense that this circular flow will not happen.
• If the oil flows in a circle and does not enter the engine, then it means that the pump flow drops to zero once the circular passage is filled with oil. These oil pumps are positive displacement pumps, which means that they WILL pump flow, even into the wide open air, with no back pressure. So the above idea cannot happen.

Duane, to answer the plug retention question, the pressure will never equalize on both sides of the plug. When it is in place, there will be a pressure drop from the inlet side of the filter (below plug) versus the outlet side of the filter (above plug). The ledge against which the plug is seated is what keeps the plug from moving, or blowing out, as you say.

Gravity does not enter into this in any meaningful way once the pump is running. You have about 0.5 oz of oil in that vertical passage where the plug resides, and that would crate a pressure of difference of around 0.2 psi top to bottom.

 

[brian6pac]

O.K. I think you guys are thinking it all wrong,
1) You have a oil pump pumping oil, it will not make pressure till it hits a dead end, and that is the bearings. If you change your oil and filter and start the engine there is no pressure till the filter fills up the oil is pushed through the engine and hits the bearings, now it has pressure.
2) You are talking about the filter draining back, oil looping in and out of the filter and this is impossible without a hole back to the pan, the pump wont stop pumping oil even if there is no pressure and it will fill the engine galleys and it will hit the bearings at the end of the line. Then and only then will it drain back in the pan to get picked up again.

 

[brian6pac]

JADAHARABI

Would you stop with the red X and prove me and everyone else wrong.
Please! I need to see it your way. Show me the way.

 

[Duane]

I really cannot explain why that statement is there in that book. It really does not make sense, once the pump is runinng and all air is purged. BUT, if the plug is missing, then the anti-drainback feature of these filters, will be mostly defeated; oil can all drain back out through the pump and pickup and leave them 'dry'. I suspect there will be a delay in pressure build up at start-up in this case, and that may be the real issue that the FSM contributors were trying to address. Chrysler has used anti-drainback filters in all sorts of engines for a long time.

The filtered path and the direct passage (that normally gets plugged) are 2 parallel paths into the main oil gallery. The oil will not flow in a circle for these 2 simple reasons:

• Even with large passages, ANY flow will create a pressure drop in the passages; so pressure will be lower at the top, where these 2 paths rejoin; it may be just a fraction of a psi lower, but it WILL be lower. To say that oil will flow backwards through either passage means that the oil has to flow from that lower pressure point back to a higher pressure point (the pump output). For those who understand hydraulics, look at it in terms of where the pressures are higher or lower, and it will make sense that this circular flow will not happen.
• If the oil flows in a circle and does not enter the engine, then it means that the pump flow drops to zero once the circular passage is filled with oil. These oil pumps are positive displacement pumps, which means that they WILL pump flow, even into the wide open air, with no back pressure. So the above idea cannot happen.

Duane, to answer the plug retention question, the pressure will never equalize on both sides of the plug. When it is in place, there will be a pressure drop from the inlet side of the filter (below plug) versus the outlet side of the filter (above plug). The ledge against which the plug is seated is what keeps the plug from moving, or blowing out, as you say.

Gravity does not enter into this in any meaningful way once the pump is running. You have about 0.5 oz of oil in that vertical passage where the plug resides, and that would crate a pressure of difference of around 0.2 psi top to bottom.

The oil does not drain back through the oil pump and pickup on a small block. Anyone who has used an accumulator can verify that as the accumulator would not work if that were possible.
The two passages leading to and from the filter are both horizontal
With each other. The plug is located precisely in between these two passages. Therefore there is pressurized oil on both sides of the plug.