Jeep Cherokee 1999 Electronic Service Manual page 1254

X J
DI AGN OSI S AN D T EST I N G (Cont inue d)
Fig. 19 Typical Inspection of Fuel Injector
FUEL INJECTOR / NEEDLE MOVEMENT
SENSOR TEST
Th e n eedle m ovem en t sen sor is u sed on ly on t h e
n u m ber –1 cylin der fu el in ject or (F ig. 20). It is n ot
u sed on t h e in ject or s for cylin der s n u m ber 2, 3, or 4.
Fig. 20 Needle Movement Sensor Location
Test in g t h e n eedle m ovem en t sen sor r equ ir es t h e
u se of a DRB Sca n t ool. Refer t o t h e P ower t r a in
Dia gn ost ic P r ocedu r es m a n u a l for a ddit ion a l in for-
m a t ion .
FUEL INJECTION PUMP TEST
Th e in je c tio n p u m p is n o t to be s e rv ic e d o r
th e w a rra n ty m a y be v o id e d . If th e in je c tio n
p u m p re qu ire s s e rv ic e , th e c o m p le te a s s e m bly
m u s t be re p la c e d .
In cor r ect in ject ion pu m p t im in g (m ech a n ica l or
elect r ica l) ca n ca u se poor per for m a n ce, excessive
sm oke a n d em ission s a n d poor fu el econ om y.
FUEL SYSTEM—2.5L DIESEL ENGINE
A defect ive fu el in ject ion pu m p, defect ive fu el t im -
in g solen oid or m isa dju st ed m ech a n ica l pu m p t im in g
ca n ca u se st a r t in g pr oblem s or pr even t t h e en gin e
fr om r evvin g u p. It ca n a lso ca u se:
• E n gin e su r ge a t idle
• Rou gh idle (wa r m en gin e)
• Low power
• E xcessive fu el con su m pt ion
• P oor per for m a n ce
• Low power
• Bla ck sm oke fr om t h e exh a u st
• Blu e or wh it e fog like exh a u st
• In cor r ect idle or m a xim u m speed
Th e elect r on ica lly con t r olled fu el pu m p h a s n o
m ech a n ica l gover n or like older m ech a n ica lly con -
t r olled fu el pu m ps. Do n ot r em ove t h e t op cover of
t h e fu el pu m p, or t h e scr ews fa st en in g t h e wir in g
pigt a il t o t h e side of t h e pu m p. Th e w a rra n ty o f
th e in je c tio n p u m p a n d th e e n g in e m a y be v o id
if th o s e s e a ls h a v e be e n re m o v e d o r ta m p e re d
w ith .
FUEL SUPPL Y RESTRICTIONS
LOW–PRESSURE LINES
Rest r ict ed or P lu gged su pply lin es or fu el filt er ca n
ca u se a t im in g fa u lt t h a t will ca u se t h e E CM t o oper-
a t e t h e en gin e in a "Lim p H om e" m ode. See t h e
in t r odu ct ion of t h e F u el In ject ion Syst em in t h is
gr ou p for m or e in for m a t ion on t h e Lim p H om e m ode.
F u el su pply lin e r est r ict ion s ca n ca u se st a r t in g pr ob-
lem s a n d pr even t t h e en gin e fr om r evvin g u p. Th e
st a r t in g pr oblem s in clu de; low power a n d blu e or
wh it e fog like exh a u st . Test a ll fu el su pply lin es for
r est r ict ion s or blocka ge. F lu sh or r epla ce a s n eces-
sa r y. Bleed t h e fu el syst em of a ir on ce a fu el su pply
lin e h a s been r epla ced. Refer t o t h e Air Bleed P r oce-
du r e sect ion of t h is gr ou p for pr ocedu r es.
HIGH–PRESSURE LINES
Rest r ict ed (kin ked or ben t ) h igh –pr essu r e lin es ca n
ca u se st a r t in g pr oblem s, poor en gin e per for m a n ce
a n d bla ck sm oke fr om exh a u st .
E xa m in e a ll h igh –pr essu r e lin es for a n y da m a ge.
E a ch r a diu s on ea ch h igh –pr essu r e lin e m u st be
sm oot h a n d fr ee of a n y ben ds or kin ks.
Repla ce da m a ged, r est r ict ed or lea kin g h igh –pr es-
su r e fu el lin es wit h t h e cor r ect r epla cem en t lin e.
CAUTION: The high–pressure fuel lines must be
clamped securely in place in the holders. The lines
cannot contact each other or other components. Do
not attempt to weld high–pressure fuel lines or to
repair lines that are damaged. Only use the recom-
mended lines when replacement of high–pressure
fuel line is necessary.
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