Generac Power Systems 941-2 Section ENGINE OIL SYSTEM, Introduction To Oil System, Oil Pump

Section 5.1

ENGINE OIL SYSTEM

INTRODUCTION TO OIL SYSTEM

The engine oil system serves to (a) reduce friction between parts, (b) cool the engine, and (c) establish a slightly negative pressure in the crankcase to prevent oil leakage. Major components that will be discussed in this section include the following:

•Oil Pickup Screen.

•Oil Pump.

•Crankshaft Oil Seals.

•Pressure Relief Valve.

•Breather Assembly.

•Oil Sump.

•Oil Filter Support Assembly.

INSPECTION:

To gain access to the screen, remove the oil filter support and its gasket. Pull the screen off its tubular protrusion. Clean the screen in solvent, then inspect for damage. Replace the screen if necessary.

OIL PUMP

DESCRIPTION:

The oil pump is of the trochoid type. Its inner rotor rotates on a shaft provided in the camshaft bore of the oil sump. The outer rotor is installed over two drive pins on the end of the camshaft and is driven by camshaft rotation.

OIL FLOW

See Figure 1. The oil pump draws oil from the oil sump through an oil pickup screen and delivers it to the areas requiring lubrication as follows:

1.Through a cored channel in the oil sump to the crankcase jour- nal at one end of the crankshaft.

2.Through the hollow camshaft to the camshaft bearing.

3.Through a cored passage in the crankcase to the crankshaft journal.

4.Through the crankshaft to the crankpin and connecting rod bearing.

Figure 1. Oil System Diagram

OIL PICKUP SCREEN

DESCRIPTION:

The oil pickup screen consists of a cylindrical screen which is open at one end only. The screen's open end fits over a tubular protrusion in the oil sump, just behind the oil filter support. Also see "Oil Filter Support Assembly".

Figure 2. Oil Pump

INSPECTION:

See Figure 3. Inspect the inner and outer rotors of the pump for damage and wear. Use a feeler gauge to check tip clearance of the rotor (measured on the shaft in the oil sump). Check the bore inner diameter and the thickness of the inner rotor. If wear limits are exceeded, replace the appropriate part(s).

PUMP TIP CLEARANCE

(MEASURED ON SHAFT IN OIL SUMP) DESIGN CLEARANCE: 0.0000-0.0010 inch (0.000-0.025mm)

WEAR LIMIT: 0.004 inch (0.105mm) Maximum

INNER PUMP ROTOR BORE

DESIGN BORE: 0.354-0.355 inch (9.000-9.019mm) WEAR LIMIT: 0.357 inch (9.034mm) Maximum

INNER ROTOR THICKNESS

DESIGN THICKNESS: 0.312-0.315 inch (7.95-8.00mm)

WEAR LIMIT: 0.311 inch (7.90mm) Minimum

Replace any part that is damaged or worn excessive- ly. The shaft on which the inner rotor rotates is NOT replaceable (oil sump must be replaced).

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