How do you change the oil pump in a 1995 Lumina van with a 3.8?

REMOVAL

1. Remove front cover.
2. Remove oil filter adapter, pressure regulator valve and spring.

1. Remove oil pump cover attaching screws, then the cover and gears, Fig. 16 .

1. Check pump cover and housing for cracks, scoring, porous or damaged casting, damaged threads or excessive wear or galling. Replace as required.
2. Check pressure regulator valve for scoring, burrs or sticking in valve bore. Replace as required.
3. Check pressure regulator valve spring for tension loss or bending, replace spring as required.
4. Check gears for chipping galling or excessive wear, replace as required.

1. Measure oil pump inner gear tip clearance, Fig. 17 . Maximum clearance should be 0.006 inch.

1. Measure oil pump outer gear diameter clearance, Fig. 18 . Clearance should be 0.008-0.015 inch.

1. Measure oil pump gear end clearance with gear dropped in housing, FIG 19. Clearance should be 0.0010-0.0035 inch.
2. Measure pressure regulator valve for valve to bore clearance of 0.0015-0.003 inch.

1. Lubricate all gears with clean motor oil, then install gears in housing.
2. Pack pump cavity with suitable petroleum jelly.
3. Install pump cover and cover attaching screws. Tighten cover attaching screws to specifications.
4. Install pressure regulator valve and spring.
5. Install oil filter adapter using a new gasket, tighten oil filter adapter attaching bolts to specifications.
6. Install front cover on engine. During front cover installation, ensure inner pump gear is properly engaged on crankshaft sprocket.

Pull the oil pan off, inside is the pump, unbolt and replace