Indicated oil pressure drop at high RPM

[7339]

1994 4.0 OHV with around 40K miles. Truck was stored for about 1.5 years, until I pulled it out 2 weeks ago. Changed all fluids, oil was nasty. Runs great despite a 327 code for the DPFE/EGR. Has the usual one lifter tick that is smoothing out after a Seafoam treatment. No loud tapping or other scary noises. Oil pressure builds instantly when cold, less than 3 seconds, the same when warm. Oil pressure begins to fluctuate from its customary position between the "MA" of the gauge when I exceed about 2500 RPM, at about 3700 RPM the needle is at the "NO" of NORMAL, and then almost hits the red line of the gauge at about 4500 RPM.

Thoughts?

 

[--weezl--]

my instant thought is that your pressure sender/sensor is shot... that doesn't sound right... 99% of the time if there is issues with oil pressure, it will go away with a rise in the idle...

prime example, i was driving a 97 freightliner fl-50 tonight for work, 400,000km on the clock, and about 35,000hrs, the oil gauge and the tach almost seemed synced, the needles pointed virtually the identacle direction... at 500rpm (idle) the oil pressure was virtually nothing, but when it reved up to 2700rpm, the oil pressure was like 100psi...

best advice at the point, get a mechanical gauge hooked up to see if that is actually happening, or if your sender or gauge is shot... though i honestly can't think of how that would cause that to happen either

 

[Jraymer360]

My truck does this as well. i'm just chalking it up to a bad sending unit since nothing else seems to be wrong so far, if it really wasn't getting pressure it'd be blown by now.