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Oil Pressure

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I know I have read this before but here goes anyway. My old motor ran around 40 plus on the oil pressure, new motor runs on the edge of the next mark up. A big diff. from before, and I know it could be the sending unit which I can swap out sence I have a new one on my old motor. What would the next mark up be? And where does your gauge run?

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Depending on the ECM flash the oil psi is probably fake. The only time the ISB is at 40 psi is warm at about 1200-1300 rpms. Hook a real gauge up to verify numbers, never trust the dash on a 98.5+ truck.

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I totaly agree on not trusting the dash. But if it's cal. to the ecm what would cause the diff. oil pressures between two motors with the same ecm?:shrug:

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I totaly agree on not trusting the dash. But if it's cal. to the ecm what would cause the diff. oil pressures between two motors with the same ecm?:shrug:

Same sensor or different? :shrug: If its your old sensor I would say tighter tolerenaces... Oil regulator jamming on the old engine (big plug on the oil filter housing).

There are a couple reasons why.. Do you know when your ECM was last flashed??

Based on him saying 40 at idle and 40 at 2K I am 99% sure the ECM has the flash that elimiates the reading from the oil psi sender.. Makes me wonder if its just the differnce in ambient temps and seasonal changes as to why the psi looks different. 40 psi is not normal for 2K rpms, its about 15-20 psi low. The only time I have seen that low of oil psi at 2K rpms was sustained 1250* EGT's and 215* water temps for 5-7 miles.

  • Author

I dont think I am explain it right. Ok my old eng. I had brand new ecm flashed by dodge. Before flash it ran 40 at idle and a little over 40 at 2k. After flash it was still the same as before the flash. Ok new to me motor with the same new ecm I had flashed now runs the next mark up from 40 and a little higher at 2k. So it not the same, it tells me I have a lot higher oil pressure with the same gauge and the same new ecm, everything the same but the eng. I even put the sendor from old motor in the new motor. I will get manual gauge and see what new pressure reading is. Can I tap into the plug at the oil filter?

That plug will work great. If your doing a permanant install I suggest one of the ports on the side of the block by the ECM. I understand what your saying as to it being different, but what I am saying is neither of those pressures are correct, so you definatly have the ECM flash that does away with true oil psi readings, so without a gauge you really can't tell. The ECM may be making it higher for multiple reasons, none of which relate to actual oil psi.

Let me get this straight... What is the switch you are changing? IAT switch? Is it possible that the IAT fooler is dragging down the instrument voltage? More questions than answers???

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