73 2.4T oil pressure

[3stewartS]

I have volunteered to bring an old car back to the road after 18 years in a barn.
The car was parked due to a lack of oil pressure. Even after going to a straight 60w oil.
So I have disassembled the motor expecting to find worn out bearings and such but they look great! Both the relief valve and safety valve move freely in their respective bore. I have not disassembled the oil pump but there is no obvious damage.
This engine appears to have never been apart and was well maintained. It is not the original engine to the car so true mileage is unknown. The car has over 200k kilometers (its European).
My question is: What am I looking for that would cause low oil pressure across the entire Rpm range?
Any insight is appreciated!!

[Flat6pac]

On a 73, the oil pressure is taken right above the pump. If the bearings are good, the oil pump will be too. Look for the defective sending unit.
If the bearings had dirt scratches, you would find the same inside on the pressure side of the pump, then the pump would be the low pressure.
My thoughts on it.....
Bruce

[3stewartS]

Thanks Bruce, your logic seems sound.

I have applied air pressure to oil sender and observed the correct reading on the gauge. 75 psi showed 5 bar on the gauge and 15 psi indicated 1 bar. So I must assume the lack of oil pressure is engine related. Again the bearings look good, no scoring no scratches, minor if any wear.
As this concern was 18 years ago the concern may be exaggerated.
My worry is to miss something during the inspection and assembly and still have a lack of oil pressure.

If anyone is willing to take me to school by phone I would welcome all calls. PM for phone number (or check one of my old for sale ads)

Thanks,
Scott

[E Sully]

Ultimate Oil Pressure Relief Valve Thread

[3stewartS]

Thanks Ed, I had seen that one and then went back and read it all again. That is a lot of good information. So I have studied the oil flow, and have gone back and measured the crankshaft main and rod journals, all within spec, so I platigauged the rod bearing clearance and found it at the hi limit. (with the old bearings) It's getting new bearings anyway. I also found both oil control springs to be a little short (68mm).
I don't understand yet how the bypass modification can increase oil pressure. If the oil tank is filled, the pressure pump will always have a sufficient quantity of oil so how will routing the excess (after the valve opens) back to the inlet of the pressure pump increase oil pressure (measured after the pump)? I do understand how adding the restrictor at the cam towers will increase oil pressure but not the bypass mod.

[E Sully]

The bypass modification does not change maximum oil pressure, it just changes where the excess oil is routed to. Instead of dumping oil into the sump, it stays in the pressure side. This keeps the level in the sump lower and keeps more oil in the oil tank for the pressure side.
The restrictor's increase low rpm pressure and volume to the crankshaft by decreasing excess volume to the heads, but does not increase overall maximum oil pressure.