Re: Zero Oil Pressure 1948 Packard

Posted by Packard 1948 On 2020/10/6 15:45:43

HH56, Yes you were one of the experts I remember who was exceptionally helpful back in 2016 when I did all of the work on my dads car.

>As I recall there is a pin or cotter key that keeps the floating screen assy on the tube assy feeding into the pump intake. Perhaps that pin or cotter key loosened and screen assy fell off.

Does anyone have any pictures of this contraption?

The service manual is silent on the pickup assembly and has no pictures and I cannot find any reliable pictures on the Google.

So to understand this oil system it helps me to spell it all out so please correct me if I am wrong...

There is a "floating" oil pickup screen assembly (why does it float) and from there the oil is sucked up through the screen and flows to the oil pump.

The oil pump is externally mounted on the right side of the engine near the front and it has a drive gear that is driven off of a matching gear on the camshaft.

The oil pump drive gear serves two purposes...
-first it drives the oil pump impellers and
-second it has a male slot in the center of the gear that meshes with the female slot in the distributer drive shaft (this was the "union" that caused so many bad words to get uttered during the reassembly...fortunately I took a picture of the distributer rotor position before I removed the oil pump).

-Once the oil is sucked through the impellers in the externally mounted oil pump the oil is now essentially unfiltered and pressurized and it now flows past a spring loaded ball bearing type pressure relief valve.

-The pressure relief valve is non-adjustable and is preset from the factory with a certain tension on the spring. If the oil pressure is too high the pressure will force the ball bearing off of its seat and that excessively pressurized oil will be dumped back into the oil pan.

-Oil flow that meets the oil pressure requirements of the overpressure relief valve will be routed back into the engine where it will take one of two paths...

-The first oil path is the oil gallery that runs along the right side of the engine parallel to the oil pan mounting flange and this is the path that feeds all of the internal components of the engine other than the lifter gallery.

-The second oil path is straight through the block and out of the other side (left/driver side) of the block at the lower oil fitting port and here will be an externally mounted Tee fitting.

-The first leg of the Tee fitting will have installed the oil pressure sender unit.

-The second leg of the Tee fitting will be one of two designs depending on IF the engine has an externally mounted oil filter assembly.

-On engines NOT equipped with an externally mounted oil filter assembly there will be a small "U" shaped pipe that will direct the oil right back into the engine through the upper most oil fitting port on the engine and this feeds the lifter gallery.

-On engines that ARE equipped with an externally mounted oil filter assembly will have an external pipe that routes the oil to the top of the externally mounted oil filter assembly and the oil will circulate around the outside diameter of the paper filter element and then flow through the paper element toward the center and once in the center the oil will flow down through the second externally mounted oil pipe through the upper most oil fitting port on the engine and this feeds the lifter gallery.


Did I get this right???

So not all of the oil flow is filtered???

So just oil screen is the only thing that filters the engine oil going to the crank and camshaft bearings (YIKES)!!!

If this all is accurate then replacing the oil pump will have removed the oil pump, the oil pump gear drive, and the oil pressure relief valve from the equation.

Perhaps the Tee fitting to the oil sender is blocked by grit???

If I remove the lid from the oil filter and crank the engine with the starter motor and if the oil level in the filter increases then I can confirm the oil pump is working???

If the oil level in the filter does not increase then it is time to take off the oil pan...drats!!!

SORRY for the long stream of consciousness but is does help to understand the system.