Operation; Installation; Manifold Air Flow (Maf) Sensor Description; Removal - Jeep 2002 WJ Service Manual

14a - 8 FUEL INJECTION
FUEL RAIL (Continued)

INSTALLATION

WARNING: NO FIRE, FLAMES OR SMOKING. RISK
OF POISONING FROM INHALING OR SWALLOWING
FUEL. RISK OF INJURY TO EYES AND SKIN FROM
CONTACT WITH FUEL. POUR FUELS ONLY INTO
SUITABLE AND APPROPRIATELY MARKED CON-
TAINERS. WEAR PROTECTIVE CLOTHING.
(1) Position and loosely install fuel return line
from fuel filter, with new seals to rail (Fig. 7).
(2) Position fuel rail to cylinder head, feed in high
pressure line with new seals (Fig. 7).
(3) Tighten fuel rail bolts to 14 N·m (124 lbs.in.)
(Fig. 7).
(4) Tighten nut of pressure line to high pressure
pump/rail to 22N·m (194 lbs.in.).
(5) Tighten banjo bolt of fuel return line to fuel
rail to 20N·m (177 lbs.in.).
CAUTION: Inspect sealing cones at the lines.
Replace as necessary. Ensure that all fuel pressure
lines are exactly located in original position.
(6) Install injector lines (Fig. 7). Tighten nut of
pressure line to rail/injector to 22N·m (194 lbs.in.).
(7) Reconnect fuel rail pressure sensor and pres-
sure control valve electrical connectors (Fig. 7).
(8) Install engine cover (Refer to 9 - ENGINE -
INSTALLATION).
(9) Connect negative battery cable.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH FAN. DO NOT PUT YOUR
HANDS NEAR PULLEYS, BELTS OR FAN. DO NOT
WEAR LOOSE CLOTHING.
(10) Start engine and inspect for leaks.
MANIFOLD AIR FLOW (MAF)
SENSOR
DESCRIPTION
The Mass Air Flow (MAF) Sensor is mounted
inline in the air intake between the air filter and the
turbocharger (Fig. 8).
Fig. 8 MASS AIR FLOW (MAF) SENSOR

OPERATION

The ECM uses the mass air flow (MAF) sensor to
measure air density. A signal voltage is provided to
the MAF sensor that contains a ceramic element. As
engine speed increases, air flow across the ceramic
element increases. Changes in air flow and air den-
sity cause the temperature of the ceramic element to
fluxuate. The ceramic element changes resistance
respectively to changes in temperature. The change
in resistance varies the signal voltage output to the
ECM. The signal voltage is used by the ECM as a
measure for the air mass supplied. The Diesel Power
Relay supplies battery power the to MAF sensor,
ground is provided by the ECM. The MAF sensor sig-
nal is provided by the ECM.

REMOVAL

(1) Disconnect negative battery cable.
(2) Disconnect mass air flow (MAF) sensor electri-
cal connector (Fig. 9).
(3) Disconnect air inlet tube.
(4) Remove MAF to air cleaner housing retaining
bolts and remove sensor (Fig. 9).
INSTALLATION
(1) Position mass air flow (MAF) sensor to air
cleaner housing and tighten bolts (Fig. 9).
(2) Connect air inlet tube.
(3) Connect MAF sensor electrical connector (Fig.
9).
(4) Connect negative battery cable.
WG