Chrysler DODGE D150 1993 Service Manual page 641

9 - 36 3.9L ENGINE •
Install inner rotor and shaft into pump body. If
clearance between inner and outer rotors is 0.203
mm (0.008 inch) or more, replace shaft and both ro­
tors (Fig. 9).
OUTER
ROTOR
INNER
ROTOR
RH179
Fig. 9 Measuring Clearance Between Rotors
Place a straightedge across the face of the pump,
between bolt holes. If a feeler gauge of 0,102 mm
(0.004 inch) or more can be inserted between rotors
and the straightedge, replace pump assembly (Fig.
10).
Fig. 10 Measuring Clearance Over Rotors
Inspect oil pressure relief valve plunger 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 approx­
imately 49.5 mm (1.95 inches). The spring should
test between 19.5 and 20.5 pounds when compressed
to 34 mm (1-11/32 inches). Replace spring t h a t fails
to meet these specifications (Fig. 11).
If oil pressure was low and pump is within specifi­
cations, inspect for worn engine bearings or other
reasons for oil pressure loss.
ASSEMBLE
(1) Install pump rotors and shaft, using new parts
as required.
RN98
Fig. 11 Proper Installation of Retainer Cap
(2) Position the oil pump cover onto the pump
body. Tighten cover bolts to 11 N-m (95 in. lbs.)
torque.
(3) Install the relief valve and spring. Insert the
cotter pin.
(4) Tap on a new retainer cap.
(5) Prime oil pump before installation by filling ro­
tor cavity with engine oil.
INSTALLATION
(1) Install oil pump. During installation slowly ro­
tate pump body to ensure driveshaft-to-pump rotor
shaft engagement.
(2) Hold the oil pump base flush against mating
surface on No.4 main bearing cap. Finger tighten
pump attaching bolts. Tighten attaching bolts to 41
N-m (30 ft. lbs.) torque.
(3) Install the oil pan.
PISTON / CONNECTING ROD ASSEMBLY
The pistons are elliptically turned so t h a t the di­
ameter at the pin boss is less t h a n its diameter
across the thrust face. This allows for expansion un­
der normal operating conditions. Under operating
temperatures, expansion forces the pin bosses away
from each other, causing the piston to assume a more
nearly round shape.
All pistons are machined to the same weight, re­
gardless of size, to maintain piston balance.
The piston pin rotates in the piston only and is re­
tained by the press interference fit of the piston pin
in the connecting rod.
REMOVAL
(1) Remove the engine from the vehicle.
(2) Remove the cylinder head.
(3) Remove the oil pan.
(4) Remove top ridge of cylinder bores with a reli­
able ridge reamer before removing pistons from cyl­
inder block. Be sure to keep tops of pistons covered
during this operation.