Sticking oil pressure relief plunger, a cure?

[beemer]

TEMPL4R; you out there, got a question here.
The 95 D1 with factory new 4.6 and timing / oil pump cover, rocker shaft assemblies, motor now has 42K miles with 2,800 mile oil changes.
I added a oil pressure gauge and pre-oiler when this motor was new.
I used to have 48 psi oil pressure even when hot dragging the clutch down below 500 rpm's and 26 psi with the pre-oiler before starting the motor every morning including hot restarts.
Now the pre-oiler only reaches 15 psi, motor oil pressure down below 30 psi at 500 rpm's, can get the normal 48 psi at 1,500 and above rpm's.
It acts like the oil plunger isn't fully seating, pulled it out and polished it lightly with 1500 grit sand paper then reinstalled.
Bingo back to the solid 48 psi even when pulling the motor below 500 rpm's but the next day same problem again.

Questions I have:

Is there a minimum clearance I should have between plunger and the bore?
Can I polish down the plunger for more clearance like .001" or more less than its original diameter then smooth all edges including the 4 port holes?
Is there a proper or correct way of smoothing the plunger that others have done or just use common sense?
This motor has never been over heated, I run half 20/50 half 10/30 oil in a mild climate of San Francisco bay area.
Long time no posting, sorry busy fighting health problems.
Carl.....=o&o>.....

[TEMPL4R]

Tightening down the cover might have sligthly distorted it. No one dropped it did they?
Have a look for a polished part of the bore or the plunger. It could be Ok when cold, then grip when it all warms up. I would look at the plunger bore first.

You can take a bit more off until it slides freely, it seals at the end. If you've just done the job and the crank bearings are pretty good, the release will be spending most of it's time off the seat. The pump will provide much more oil than is needed.

Chris

[beemer]

This is a LR dealer warranty replaced motor back in 2002 no dropped or damaged parts. Had no problems until lately, I will ball gauge the bore then mike the plunger to check the clearance. Hard to work on the bore as this is a assembled motor in the vehicle.
I think .003" would be a good clearance.

[beemer]

The 4.6 motor build was done back in 2002 by a LR dealer, no dropped or damaged parts. Only one mechanic did all the work and he knew I was a licensed aircraft mechanic.
Tomorrow i'll look into the old 3.9 front cover w/pump relief valve assembly then study it close on the bench.
I'm thinking of machining a iron slug .0015" to .002" larger than the plunger and see if it will go into the bore freely to the end.

[TEMPL4R]

Has the spring weakened off or snapped a coil?
Is seat Ok? If it were an older engine I'd say it could be scoring in the bore. Check the edges of the plunger seat and spring end for sharp edges. They can stick if it twists slightly. Round the edges off a bit with the fine emery paper.

If it doesn't seat, it's either a weak or broken spring, dirt or carbon in the bore/plunger, a sharp egde, a bad or loose seat or a distorted cover.


We had this problem with a Case tractor, every so often the priority valve for the steering would stick, so we had no steering. The plunger was wearing and would twist as it worked. it got to a tight spot and jammed open. A bit of fine tuning wigh emery and it was as good as new.

Chris