Oil Pressure - D1

joeblack5

Well-known member
Sep 12, 2023
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32
State college usa
Hi Greg, the gear pump is positive displacement, besides internal leaks the volume is linear with rpm.
Yes the pressure is high going into the restriction and then low on the other side.
If indeed the relief valve is after the oil cooler / filter then it does not surprise me that the gerotor pump cracks ones in a while, unless there is a bypass valve....If the relief valve is before the the oil cooler / filter then it does not surprise me that the d1 builds up.oil pressure very slow when it is cold.

Again with all the oil problem threads here and other sites I am surprised that I have not found an exact description yet.

Johan
 

LRDONE

Well-known member
Dec 3, 2020
339
119
Michigan
Again with all the oil problem threads here and other sites I am surprised that I have not found an exact description yet.

Johan
Take the cover off and look at it. I've had mine a part a few times. If the pressure relief valve is open, the pump will pump oil directly in to the oil port where the pump is pulling oil from. That's your exact description.
 
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boxster

Well-known member
Jun 1, 2009
475
96
Fallbrook Ca.
Hi Greg, the gear pump is positive displacement, besides internal leaks the volume is linear with rpm.
Yes the pressure is high going into the restriction and then low on the other side.
If indeed the relief valve is after the oil cooler / filter then it does not surprise me that the gerotor pump cracks ones in a while, unless there is a bypass valve....If the relief valve is before the the oil cooler / filter then it does not surprise me that the d1 builds up.oil pressure very slow when it is cold.

Again with all the oil problem threads here and other sites I am surprised that I have not found an exact description yet.

Johan
IMG_5443.png
 
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LRDONE

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Dec 3, 2020
339
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Michigan
714B1125-35CE-42FA-B636-0F29D45B5820.jpeg
If the relief valve is closed the oil will only head south to the oil cooler port. If the relief valve is open, the oil will feed right back into the supply.
 
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boxster

Well-known member
Jun 1, 2009
475
96
Fallbrook Ca.
View attachment 66367
If the relief valve is closed the oil will only head south to the oil cooler port. If the relief valve is open, the oil will feed right back into the supply.
In my experience I don’t remember a time that the oil pressure light remained lit no more than a few seconds. However after an oil change it would stay lit a bit longer while pumping out the air space in the oil gallery.
 

LRDONE

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Dec 3, 2020
339
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Michigan
In my experience I don’t remember a time that the oil pressure light remained lit no more than a few seconds. However after an oil change it would stay lit a bit longer while pumping out the air space in the oil gallery.
The longest mine was lit was when the pump needed to prime, after having the pan and pick up tube off.
 

joeblack5

Well-known member
Sep 12, 2023
61
32
State college usa
Thanks guys, lrdone, perfect that explains a lot.

This morning another cold start.
Oil pressure stays 0 on gauge and starts building up after 5 seconds slowly to 28 psi. Revving engine lowers pressure with 1 to 2 psi.

I increased pressure on the relief valve and pressure increased to 50 psi at 3000 rpm and higher depending on rpm.

The current filter is a Purolator with a 16 psi bypass.

I let the engine heat up for 20 min in the shop so I am sure the oil temp is still lower then on the road.

With my relief spring hack the warm engine idle pressure was 20 psi and increased to 50 psi at 4000 rpm.

At least one part of my problem has been solved.
I ordered a large wix filter with a bypass of 8 psi and will check if it builds pressure on the gauge faster at cold startup.

Johan
 

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joeblack5

Well-known member
Sep 12, 2023
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State college usa
Oh, and thanks Boxster, that is a better pic but still not relief valve..
Yes I read that thread, good info is hard to come buy.

I will try the new filter with the original spring setup and report the difference going from 16 to 8psi filter bypass.

Johan
 

joeblack5

Well-known member
Sep 12, 2023
61
32
State college usa
Got a new large wix filter and pre filled with rotella 15w40. Cranked without fuses for fuel.and injection for 20 sec, no oil pressure. Then started and ran for 15 sec before oil pressure came up. 3 psi higher then with old filter.. 35 psi instead of 32.
When revving up oil pressure drops 2 psi as in old set up.

Next I will make an adjustable shim for the oil pressure relief valve.
 

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LRDONE

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Dec 3, 2020
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Michigan
Got a new large wix filter and pre filled with rotella 15w40. Cranked without fuses for fuel.and injection for 20 sec, no oil pressure. Then started and ran for 15 sec before oil pressure came up. 3 psi higher then with old filter.. 35 psi instead of 32.
When revving up oil pressure drops 2 psi as in old set up.

Next I will make an adjustable shim for the oil pressure relief valve.
And your pump is 100%? No wear on the faces/teeth and the thrust plate is flat? It shouldn't take that long to build pressure from a oil filter only removal.
 
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joeblack5

Well-known member
Sep 12, 2023
61
32
State college usa
Another cold start test with the wix low bypass filter. No modification to relief valve yet. Pressure starts to builds up in 1 second and passes 10psi in two seconds. Maxes out at 37 psi at idle cold.

Next will be adding the relief valve pressure adjuster to it.

Johan
 

Greg_M

Well-known member
Dec 27, 2021
239
106
Vancouver Island
Another cold start test with the wix low bypass filter. No modification to relief valve yet. Pressure starts to builds up in 1 second and passes 10psi in two seconds. Maxes out at 37 psi at idle cold.

Before "Got a new large wix filter and pre filled with rotella 15w40. Cranked without fuses for fuel.and injection for 20 sec, no oil pressure. Then started and ran for 15 sec before oil pressure came up. 3 psi higher then with old filter.. 35 psi instead of 32."

What changed to account for the difference in the two Wix filter tests?

2 psi drop on revving like your first test?

Thanks, Greg
 

joeblack5

Well-known member
Sep 12, 2023
61
32
State college usa
Hi Greg, the only thing that changed was that the second time the wix filter and oil system was full.
So the second time with the new wix compares the time / pressure with the old filter.

Not sure the 3psi is in the error readout range.
The 2 psi drop while revving up is strange. With more spring tension it behaves more normal, that is the pressure goes up when revving.


Overall the cold start pressure seems to come a bit faster. But the temperature was a bit higher as well.

Next step is the " adjustable" spring for the pressure relief and see what is going on with that new variable.


I do not know, just trying to generate some date to make an " educated guess"

Johan
 

joeblack5

Well-known member
Sep 12, 2023
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State college usa
Well some progress. Made an adjustable shim. Took the circlip and oil relief spring out.
Used a threaded rod in a frame home that is nice inline with the oil pressure relief cap to push the whole assembly back in

Oil pressure cold low middle.40 psi.
Adjusted my shim about a turn..44 psi.
 

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Greg_M

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Dec 27, 2021
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Vancouver Island
Well some progress. Made an adjustable shim. Took the circlip and oil relief spring out.
Used a threaded rod in a frame home that is nice inline with the oil pressure relief cap to push the whole assembly back in

Oil pressure cold low middle.40 psi.
Adjusted my shim about a turn..44 psi.
How are you measuring (determining sufficient) flow? Choking the flow completely will give you the highest pressure but the engine won't be happy.
 
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joeblack5

Well-known member
Sep 12, 2023
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State college usa
Sorry Greg, little late with uploading the pics.
The Lowe's part is the exact fit of the bore . It is caught behind the circlip. The 1/4" bolt pushes at the original oil plug and can move it more inwards increasing the spring tension and thus the oil pressure bypass....
The 3/8 threaded rod is pointy at the end so that it does not slip of the 1/4 nut that is part of the washer assembly. I was just lucky to look in the right drawer at Lowe's. First was going to make one but the could not resist this solution.

Yes I agree, there is always the lack of details. Tomorrow another cold start to see how fast the pressure is coming up.



Johan
 

joeblack5

Well-known member
Sep 12, 2023
61
32
State college usa
How are you measuring (determining sufficient) flow? Choking the flow completely will give you the highest pressure but the engine won't be happy.

As I understand it the oil relief valve is a bypass valve, it dumps high pressure oil back to the inlet so choking it increases pressure and reduces the oil going back to the pump inlet. Thus higher flow thru the bearings. The flow total flow thru the pump might be less because of higher internal losses and leakage.



Johan