Oil pressure reading

I have 71 m35a2 with the d turbo. Oil pressure quit reading would come and go jig you tapped the gauge. Swapped gauges wih new 120 psi, that's what was in there.during first startup oil gauge will normal in rpms around 90 mark or above and at idle around 60 mark. But after running for a while and at operating temp. The gauge will around 0 psi at idle but during driving gauge will read normally. No knocking noises or abnormal noises present. Didn't know if this could just be sendin unit issue or something else. No, I have not put a manual gauge in yet to see the difference

I have the same issue but I've changed my sending unit but it still reads 0 after normal operating temps have been reached. Make sure you check your oil often because you could me making oil with a leaking hydraulic head, flame heater or fuel boost pump. I've changed evrything on mine except the booster pump seal, it's not making enough oil or any at all to justify taking the booster pump off. I have not put a manual gauge on it yet. FYI: If your making oil, diesel is entering the crankcase and thinning the oil giving you the low oil readings. Hope this helps.

One item that might be worth checking if it doesn't appear you have a oil dilution issue is the oil pressure regulator. If the spring is getting weak or the plunger sticking in the bore it could cause a low pressure problem. In [FONT=Times New Roman, serif]TM 9-2320-361-34, Sec 3-13, page 3-40 [/FONT][FONT=Times New Roman, serif]it explains how to test the springs in the regulator.[/FONT]

Check it with a known good mechanical gauge.

Plus one. And don't wait.

WillWagner said:

Check it with a known good mechanical gauge.

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Yep. remove the oil pressure sending unit and screw in a mechanical oil pressure gauge. You can use one the should be mounted in the dash. They're available at auto parts stores, napa, etc...

You can bench test your sending unit by hooking it up to an air compressor. Check my thread and the death of my engine here - http://www.steelsoldiers.com/deuce/53241-no-oil-pressure-oa331-2.html#post1065168

I have a 60psi gauge in mine. It had a 120psi gauge and always read dangerously low. Turned out the original owner installed the wrong gauge...

mismatched gauge and sender is often a problem

gungearz said:

I have a 90psi gauge in mine. It had a 120psi gauge and always read dangerously low. Turned out the original owner installed the wrong gauge...

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Not arguing here. Just want to guide the OP. I've only seen 60 or 120 psi sending units and gauges.

Kohburn said:

mismatched gauge and sender is often a problem

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Yep. A bench test would indicate which unit is in place. Perhaps some marking from the sending unit could tell something.

Thanks shenkman, big thumbs. 6 and 9 are on top of each other. I do have a 60psi gauge. I have corrected my last post here.