In a message dated 9/28/2010 11:28:48 P.M. Eastern Standard Time,
cbarber@texasattorney.net writes:
Oh, and maybe this is too obvious, but when I drop the pan, what should I
be looking for. Yeah, large metal shards I would figure out, but if it
is not that obvious, where do I need to focus. The pressure gage?? The
pump?? Something
else??
Chris
In the never ending tradition of two step forward and three steps
back, I was working on my RPM drop out at 6000 rmp
(messed
with seveal
resistors to no avail). As I was sitting on the
ramp at idle for a few minutes, focusing on the RPM's
I
glanced over at the Oil Pressure and noted it was flashing as an alert and was
showing almost NO oil pressure (4 or 5 psi). I instantly shut down the
engine.
The
engine appeared to be running fine before I shut it down. I checked the
wire to the back of the engine monitor and all was fine. I also checked
the continutiy
of the wire to the sensor and it was good. I
started the engine again and it started fine and seem to run fine, however,
the OP did not kick in so I shut it down
again
If the 6000 RPM was without a prop, (Unloaded) or just for
a few seconds loaded, then no damage has occurred. Cut open the filters
and lay out the paper to look for sparkles or brass/copper flakes. No sparkles,
no damage. It is difficult to hurt plain bearings. Also in the drained oil, same
idea.
If it pumps oil but generates no pressure, it can be the
pickup tube coming loose from the front iron. I would not use a gasket there.
Just lap the flange flat and bolt it up with new bolts that have been drilled
for safety wire. Use an inch pound torque wrench. Safety wire the
bolts.
The second possibility depending on the engine is the "O" ring
junction on early 12As and 13Bs will blow out the "O" ring on a quick rev up
from cold, then part of the ring gets stuck between the iron and front cover,
dumping most of the oil pressure. In later engines this was replaced with a
stainless tab with a hole in it, and it cannot fall off.
The front cover needs to come off to fix that.
The oil pump key shearing and not turning the pump up to speed
is a possibility, if the nut had also been left loose. Red Locktite on the
nut after torqueing it and folding the soft
washer up on one flat. If the nut has been installed with red Locktite and
torqued, it would probably work with no key. The tightened nut makes enough
friction to turn the shaft, If the nut comes loose, the key (soft) will shear
right off.
One of the jet holders in the crank came loose?
If the balls and springs have been removed from the crank,
then hot idle oil pressure will be very low. It should come right up and be
above 60 PSI by 2,000 RPM.
You can check the oil pump nut from underneath but do little
else. The pump drive chain may have enough flex to move the sprocket a bit, but
if the key falls off you will never get it back on without removing the front
cover.
It is possible that a piece of scrap went through the pump and
broke a ring, or sheared a key driving one of the lobes.
Oil pump came loose from the front iron? Are those bolts
wired?
The oil level in the sump is very low?
The oil pressure relief has debris in it and is stuck
open?
The oil pressure relief has come loose from the rear
iron?
The temperature pill in the crank nose has come
loose?
I will think some more.
Lynn E. Hanover