Oil Pump: Inspection

Lay a straightedge across the pump cover surface (Fig 1). If a 0.076 mm (0.003 in.) feeler gauge can be inserted between cover and straight edge, cover should be replaced.

Fig 1: Checking Oil Pump Cover Flatness - Typical
Courtesy of DAIMLERCHRYSLER CORP.
Measure thickness and diameter of rotors. If either rotor thickness measures 18.92 mm (0.744 in.) or less, or if the outer rotor diameter is 82.45 mm (3.246 in.) or less, replace rotor set (Fig 2) and (Fig 3).

Fig 2: Measuring Outer Rotor Thickness
Courtesy of DAIMLERCHRYSLER CORP.

Fig 3: Measuring Inner Rotor Thickness
Courtesy of DAIMLERCHRYSLER CORP.
Measure clearance between outer rotor and case (Fig 4). If measurement is 0.19 mm (0.007 in.) or more, and outer rotor is within specification, replace chain case cover.

Fig 4: Measuring Outer Rotor Clearance In Case
Courtesy of DAIMLERCHRYSLER CORP.
Measure clearance between the outer rotor and inner rotor (Fig 5). If clearance between inner and outer rotors is 0.150 mm (0.006 in.) or more, replace rotor set.

Fig 5: Measuring Clearance Between Rotors
Courtesy of DAIMLERCHRYSLER CORP.
Place a straightedge across the face of the chain case cover, in between the bolt holes. If a feeler gauge of 0.077 mm (0.003 in.) or more can be inserted between rotors and the straightedge, and the rotors are within specification, replace the case cover.
Inspect oil pressure relief valve for scoring and free operation in its bore. Small marks may be removed with 400 grit wet or dry sandpaper.
The relief valve spring has a free length of approximately 68.7 mm (2.70 in.) and should test between 22.5 and 27.5 pounds when compressed to 57 mm (2.24 in.). Replace spring that fails to meet specifications.
If oil pressure is low and pump is within specifications, inspect for worn engine bearings or other reasons for oil pressure loss.