Dodge ram truck 3500 1996 Service Manual page 393

BR IGNITION SYSTEM 8D -11
DIAGNOSIS AND TESTING (Continued)
DISTRIBUTOR CAP—3.9L/5.2L/5.9L ENGINES
Remove the distributor cap and wipe i t clean with
a dry lint free cloth. Visually inspect the cap for
cracks, carbon paths, broken towers or damaged
rotor button (Fig. 22) or (Fig. 23). - Also check for
white deposits on the inside (caused by condensation
entering the cap through cracks). Replace any cap
that displays charred or eroded terminals. The
machined surface of a terminal end (faces toward
rotor) will indicate some evidence of erosion from
normal operation. Examine the terminal ends for evi­
dence of mechanical interference with the rotor tip.
Fig. 23 Cap inspection—internal—Typical
DISTRIBUTOR ROTOR—3 J L / I . 2 L / S J L ENGINES
Visually inspect the rotor (Fig. 24) for cracks, evi­
dence of corrosion or the effects of arcing on the
metal tip. Also check for evidence of mechanical
interference with the cap. Some charring is normal
on the end of the metal tip. The silicone-dielectric-
varnish-compound applied to the rotor tip for radio
interference noise suppression, will appear charred.
This is normal. Do not remove the charred com­
pound. Test the spring for insufficient tension.
Replace a rotor that displays any of these adverse
conditions.
INSUFFICIENT
SPRING
TENSION
CORRODED EVIDENCE OF
PHYSICAL
CONTACT
WITH CAP J908D-48
Fig, 24 Rotor inspection—Typical
IGNITION TIMING
NOTE: Base (initial) ignition timing is NOT adjust­
able on any engine. On 3.9L75.2L/5.9L engines, do
not attempt to adjust ignition timing by rotating the
distributor.
All ignition timing functions are controlled by the
Powertrain Control Module (PCM). The DRB scan
tool may be used to verify base timing and electronic
timing advance. Refer to the appropriate Powertrain
Diagnostics Procedures service manual for operation
of the DRB Scan Tool.
Fuel synchronization can be verified and set by
rotating the distributor. Refer to the Distributor
Removal/Installation section of this group. See
Checking Distributor Position. This operation can be
performed on 3.9L/5.2L/5.9L engines only.
MAP SENSOR
For an operational description, diagnosis or remov­
al/ installation procedures, refer to Group 14, Fuel
Systems.
CRANKSHAFT POSITION SENSOR—3.9L/5.2L/5.9L
ENGINE
To perform a complete test of this sensor and its
circuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man­
ual. To test the sensor only, refer to the following: