Jeep Cherokee 1999 Electronic Service Manual page 1246

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DESCRI PT I ON AN D OPERAT I ON (Cont inue d)
Fig. 1 Typical Fuel Pressure Test at Injector
FUEL TANK MODULE
An elect r ic fu el pu m p is n ot a t t a ch ed t o t h e fu el
t a n k m odu le for diesel power ed en gin es. F u el is
siph on ed by t h e fu el in ject ion pu m p.
Th e fu el t a n k m odu le is in st a lled in t h e t op of t h e
fu el t a n k. Th e fu el t a n k m odu le con t a in s t h e follow-
in g com pon en t s:
• F u el r eser voir
• A sepa r a t e in -t a n k fu el filt er
• E lect r ic fu el ga u ge sen din g u n it
• F u el su pply lin e con n ect ion
• F u el r et u r n lin e con n ect ion
FUEL GAUGE SENDING UNIT
Th e fu el ga u ge sen din g u n it is a t t a ch ed t o t h e side
of t h e fu el pu m p m odu le. Th e sen din g u n it con sist s of
a floa t , a n a r m , a n d a va r ia ble r esist or (t r a ck). Th e
t r a ck is u sed t o sen d a n elect r ica l sign a l u sed for fu el
ga u ge oper a t ion .
As t h e fu el level in cr ea ses, t h e floa t a n d a r m m ove
u p. Th is decr ea ses t h e sen din g u n it r esist a n ce, ca u s-
in g t h e P CM t o sen d a sign a l t o t h e fu el ga u ge on t h e
in st r u m en t pa n el t o r ea d fu ll. As t h e fu el level
decr ea ses, t h e floa t a n d a r m m ove down . Th is
in cr ea ses t h e sen din g u n it r esist a n ce, ca u sin g t h e
P CM t o sen d a sign a l t o t h e fu el ga u ge on t h e in st r u -
m en t pa n el t o r ea d em pt y.
FUEL FILTER/WA TER SEPARA TOR
Th e fu el filt er /wa t er sepa r a t or a ssem bly is loca t ed
in t h e en gin e com pa r t m en t n ea r t h e st r u t t ower (F ig.
2).
FUEL SYSTEM—2.5L DIESEL ENGINE
Fig. 2 Fuel Filter/Water Separator Location
Th e com bin a t ion fu el filt er /wa t er sepa r a t or pr o-
t ect s t h e fu el in ject ion pu m p by h elpin g t o r em ove
wa t er a n d con t a m in a n t s fr om t h e fu el. Moist u r e col-
lect s a t t h e bot t om of t h e filt er /sepa r a t or in a pla st ic
bowl.
Th e fu el filt er /wa t er sepa r a t or a ssem bly con t a in s
t h e fu el filt er, fu el h ea t er elem en t , a n d fu el dr a in
va lve.
F or in for m a t ion on t h e fu el h ea t er, r efer t o F u el
H ea t er in t h is gr ou p.
Refer t o t h e m a in t en a n ce sch edu les in Gr ou p 0 in
t h is m a n u a l for t h e r ecom m en ded fu el filt er r epla ce-
m en t in t er va ls.
F or per iodic dr a in in g of wa t er fr om t h e bowl, r efer
t o F u el F ilt er /Wa t er Sepa r a t or Rem ova l/In st a lla t ion
in t h is gr ou p.
FUEL SHUTDOWN SOLENOID
Th e fu e l s h u td o w n s o le n o id is c o n tro lle d a n d
o p e ra te d by th e MS A.
Th e fu el sh u t down (sh u t -off) solen oid is u sed t o
elect r ica lly sh u t off t h e diesel fu el su pply t o t h e h igh -
pr essu r e fu el in ject ion
m ou n t ed t o t h e r ea r of t h e in ject ion pu m p.
Th e solen oid con t r ols st a r t in g a n d st oppin g of t h e
en gin e r ega r dless of t h e posit ion of t h e a cceler a t or
peda l. Wh en t h e ign it ion (key) swit ch is OF F, t h e
solen oid is sh u t off a n d fu el flow is n ot a llowed t o t h e
fu el in ject ion pu m p. Wh en t h e key is pla ced in t h e
ON or START posit ion s, fu el su pply is a llowed a t t h e
in ject ion pu m p.
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pu m p. Th e solen oid is