Jeep Cherokee 1999, Electronic Service Manual

Page: 1248 / 1948

kP a (2175–2291 psi), t h e n eedle va lve spr in g t en sion
is over com e. Th e n eedle va lve r ises a n d fu el flows
t h r ou gh t h e spr a y h oles in t h e n ozzle t ip in t o t h e
com bu st ion ch a m ber. Th e pr essu r e r equ ir ed t o lift
t h e n eedle va lve is t h e in ject or open in g pr essu r e set -
t in g. Th is is r efer r ed t o a s t h e “pop-off” pr essu r e set -
t in g.
F u el pr essu r e in t h e in ject or cir cu it decr ea ses a ft er
in ject ion . Th e in ject or n eedle va lve is im m edia t ely
closed by t h e n eedle va lve spr in g a n d fu el flow in t o
t h e com bu st ion ch a m ber is st opped. E xh a u st ga ses
a r e pr even t ed fr om en t er in g t h e in ject or n ozzle by
t h e n eedle va lve.
A copper wa sh er (ga sket ) is u sed a t t h e ba se of
ea ch in ject or (F ig. 5) t o pr even t com bu st ion ga ses
fr om esca pin g.
F u el in ject or fir in g sequ en ce is 1–3–4–2.
FUEL TUBES/LINES/HOSES AND CLAMPS—
LOW-PRESSURE TYPE
Also r efer t o t h e pr oceedin g sect ion on Qu ick–Con -
n ect F it t in gs.
In spect a ll h ose con n ect ion s su ch a s cla m ps, cou -
plin gs a n d fit t in gs t o m a ke su r e t h ey a r e secu r e a n d
lea ks a r e n ot pr esen t . Th e com pon en t sh ou ld be
r epla ced im m edia t ely if t h er e is a n y eviden ce of deg-
r a da t ion t h a t cou ld r esu lt in fa ilu r e.
Never a t t em pt t o r epa ir a pla st ic fu el lin e/t u be or a
qu ick–con n ect fit t in g. Repla ce com plet e lin e/t u be a s
n ecessa r y.
Avoid con t a ct of a n y fu el t u bes/h oses wit h ot h er
veh icle com pon en t s t h a t cou ld ca u se a br a sion s or
scu ffin g. Be su r e t h a t t h e fu el lin es/t u bes a r e pr op-
er ly r ou t ed t o pr even t pin ch in g a n d t o a void h ea t
sou r ces.
Th e lin es/t u bes/h oses a r e of a specia l con st r u ct ion .
If it is n ecessa r y t o r epla ce t h ese lin es/t u bes/h oses,
u se on ly or igin a l equ ipm en t t ype.
Th e h ose cla m ps u sed t o secu r e t h e r u bber h oses
a r e of a specia l r olled edge con st r u ct ion . Th is con -
st r u ct ion is u sed t o pr even t t h e edge of t h e cla m p
fr om cu t t in g in t o t h e h ose. On ly t h ese r olled edge
t ype cla m ps m a y be u sed in t h is syst em . All ot h er
t ypes of cla m ps m a y cu t in t o t h e h oses a n d ca u se
fu el lea ks.
Wh er e a r u bber h ose is join ed t o a m et a l t u be
(st a ked), do n ot a t t em pt t o r epa ir. Repla ce en t ir e
lin e/t u be a ssem bly.
Use n ew or igin a l equ ipm en t t ype h ose cla m ps.
Tigh t en h ose cla m ps t o 2 N·m (20 in . lbs.) t or qu e.
QUICK-CONNECT FITTINGS—LOW PRESSURE
TYPE
Differ en t t ypes of qu ick-con n ect fit t in gs a r e u sed t o
a t t a ch va r iou s fu el syst em com pon en t s. Th ese a r e: a
sin gle-t a b t ype, a t wo-t a b t ype or a pla st ic r et a in er
r in g t ype (F ig. 6). Refer t o Qu ick-Con n ect F it t in gs in
t h e Rem ova l/In st a lla t ion sect ion for m or e in for m a -
t ion .
CAUTION: The interior components (o-rings, spac-
ers) of quick-connect fitting are not serviced sepa-
rately, but new pull tabs are available for some
types. Do not attempt to repair damaged fittings or
fuel lines/tubes. If repair is necessary, replace the
complete fuel tube assembly.
Fig. 4 Fuel Injectors and Drain Tubes
Fig. 5 Fuel Injector Sensor
X J FUEL SYSTEM—2.5L DIESEL ENGINE 14 - 5
DESCRI PT I ON AN D OPERAT I ON (Cont inue d)