Erratic oil pressure

x MadMAX DIESEL

x MadMAX DIESEL

<<<< No Horsepower
Dec 30, 2008
7,535
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Lexington, Ky
What can cause oil pressure to fluctuate from 75-30 back and fourth in a split second? Could enough blowby be sloshing oil so much that it pulls air bubbles into the pick up? The relief valve seems to work properly and the pickup is sealed good. The bypass in the cooler just bypass' filter correct? That would not cause such a problem


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Huffy67

Huffy67

New member
Dec 26, 2014
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Arkansas
Not usually I don't think and if it's only doing that at the end of your pulls it may have nothing to do with the sending unit. But it is a cheap easy thing to try and see if it fixes it.


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Henry95

Henry95

Member
Apr 4, 2015
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My lly was just doing that and I replaced the sending unit and it's good now.


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Henry95

Henry95

Member
Apr 4, 2015
283
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x MadMAX DIESEL said:
Read high and low in a split second?


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Click to expand...


Yes from go from normal to nothing. Would not stop bouncing around then stayed on zero for a while. Fixed it a couple days ago and it's good now.


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ripmf666

ripmf666

Active member
Sep 20, 2006
15,123
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Wentzville Mo
I will not use or sell mellings pumps. Had issues with one before holding very high pressure that's not needed. And did the same thing your seeing now. Was spinning the gear on the shaft.
 
mike diesel

mike diesel

I'm alright.
Sep 6, 2012
4,005
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36
SLC, Utah
ripmf666 said:
I will not use or sell mellings pumps. Had issues with one before holding very high pressure that's not needed. And did the same thing your seeing now. Was spinning the gear on the shaft.
Click to expand...

When was this? From what I understand, they swapped to the left hand threaded shaft because of issues like that. I have zero issues with my left hand melling pump. I see normal oil pressure as well.
 
x MadMAX DIESEL

x MadMAX DIESEL

<<<< No Horsepower
Dec 30, 2008
7,535
1
38
33
Lexington, Ky
mike diesel said:
When was this? From what I understand, they swapped to the left hand threaded shaft because of issues like that. I have zero issues with my left hand melling pump. I see normal oil pressure as well.
Click to expand...


Yeah I mean I've never had issues with my right handed pump even.


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ripmf666

ripmf666

Active member
Sep 20, 2006
15,123
14
38
47
Wentzville Mo
mike diesel said:
When was this? From what I understand, they swapped to the left hand threaded shaft because of issues like that. I have zero issues with my left hand melling pump. I see normal oil pressure as well.
Click to expand...

Has been a few years now. The pump was putting out 90psi in the warm weather and when temps dropped late at night early morning caused 100 psi +
After a issue I rather stick with a part I know works. Even with left hand thread have pump shaft keyed and gear don't trust a part with a small surface. To hold with the nut only and grit surface to supply blood for you built motor kinda like having a weak heart waiting for it to shut down.

Pic to show key way was a back up lb7 pump.

 
Last edited:
ty_LBZ

ty_LBZ

Camaro killa
Dec 6, 2014
297
1
16
Farmington, NM
x MadMAX DIESEL said:
What can cause oil pressure to fluctuate from 75-30 back and fourth in a split second? Could enough blowby be sloshing oil so much that it pulls air bubbles into the pick up? The relief valve seems to work properly and the pickup is sealed good. The bypass in the cooler just bypass' filter correct? That would not cause such a problem


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Click to expand...

Faulty stepper motor in the gauge?
 
56taskforce

56taskforce

Well-known member
Mar 30, 2014
1,074
51
48
Ben check the engine harness plugs top of the driver's side valve cover. I was chasing the same problem simply pushing the plugs together with a large pair of channel locks cured the problem. Note: the plugs appeared to be fine before I used the pliers on them it was a last ditch effort but it worked...
 
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