Thread: oil pressure needle irractic

Tweet

oil pressure needle bouncing, mechanical gauge, any thoughts?

What brand of guage, and what is the engine, with any mods to the block.? Also has anything been removed changed or alterd just prior to this, or did it just start randomly? Also how much is it bouncing ?

autometer, liquid filled, block freshened up, was good and steady, started to bounce, never had one do this before. stock rods, crank, just new bearings, new cam, mild build, melling oil pump, standard volume, but rear sump pan, modified to hold more oil

was the pan widened to increase oil capacity or is it a deeper model? If its deeper was the oil pump pick up changed to the longer tube to reach the bottom of the pan?

it was actuall shortened then widened, and the pickup was also shortened, the pickup screen was a 1/4 " of the pan floor with out the pan gasket in place

its bouncing maybe 2-4psi, but a fast bounce. this is a new start up , no knocks ar bangs yet

If this is at idle, probably a non-issue... The liquid filled gauges are so much more sensitive to pressure changes you may just have never noticed it before with slower acting gauges.... What is it doing at 1500 and up RPM???? At idle, the oil pressure will bounce around a bit...I suppose something to do with the oil passages in the crank as they rotate and change their position to the grooves and or holes in the main bearings.......With grooved uppers and smooth in the caps, the fluctuation is even more noticeable..... Know maybe somebody can tell both of us why it does this!!!!!!

First and foremost, try a different oil pressure gage and report back as to whether the second gage's needle bounces too or if the first gage is apparently defective (assuming the second gage's needle does not bounce).

Paul

I cut the oil filter apart, nothing to say its abnormal, no metal or bearing material. Drained the oil, thinking may that the oil was diluted with water. all seemed good , still have not fired it up again, will try another gauge tomorrow, let you know how things turn out.

When you get the gauge disconnected, fire the engine up and bleed the line into a can, and get all the bubbles out. Air can make a gauge do some weird things.

If your gauge is fine, then this oil pressure pulsing could be the symptoms of a multitude of possible reasons, including but not limited to: bent distributor shaft, improperly installed distributor, non-concentric distributor gear (unlikely), bent oil pump shaft, debris blocking the closure of the oil pump's internal bypass port (piston stuck), cracked pickup tube, partially blocked pickup tube, etc.

But, I suggest changing your oil filter. Have you run the engine since cutting the first filter apart? I've seen this before where the anti-drainback flapper in an oil filter was causing the exact same symptoms (anti drainback flapper was damaged during manufacture), and I'll bet that installing a new oil filter will eliminate the problem.

Paul

P.S: If you have an orange Fram filter, remove it and replacie it with a better filter, perhaps a FoMoCo FL1A, available at Wal-Mart for cheap. I suggest that you do this even if the newly installed orange Fram filter has eleminated the oil pressure fluctuation.

Originally Posted by dberens

its bouncing maybe 2-4psi, but a fast bounce. this is a new start up , no knocks ar bangs yet

There are a multitude of reasons why you could see minor pressure fluctuations including all of the above mentioned things. For starters a gear pump is by its very nature not entirely smooth. If you had a piezoelectric gage you could actually see the gear tooth frequency in the pump!

Your liquid (glycerin) filled gage is designed to dampen fluctuations though and 2-4 psi is even on the lower side of its resolution. That means I don't trust the gage to resolve 2 psi that well.

However one thing that you mention is that it is a fresh build. This could simply indicate that the rings are still seating and the fresh build blow by you are getting alone would readily account for the modulation of pressure you are seeing. As long as the pressure is not too low and comes up quickly to a steady value with engine speed I would not be overly concerned.

Kitz

What is the matter with the fram filters? Are thay to restrictive?

Check out;

http://people.msoe.edu/~yoderw/oilfi...lterstudy.html

and

http://www.bobistheoilguy.com/forums/ubbthreads.php


Fram filters are not good IMO. I use GM performance filters.

Kitz

The proliferation of cheap oil filters seems to have paralleled the introduction of the quickie lube places.... maybe not connected but the advent of $20 oil changes drove a need for decreasing the cost of the components. Name brand oil filters used to be of reasonable quality and then there were the KMart filters that were of questionable quality. At some point, the "name" brands were pressured to lower their price; hence lower their quality so they could be sold at the quickie lube or at MegaMart.

I visited a Fram factory once, they were even having problems with pin holes in their metal cans....thin metal problems. If you wholesale a filter for less than $1, how much quality can their be in the housing stamping, the painting, the mounting ring, the check valve, and the filter material? Answer: not much. Fram said that (at that time) they didnt want to add cost to the filter so they instead paid claims for blown engines if the customer proved it was the filter's fault....

mike in tucson