JEEP CHEROKEE 1988 Service Repair Manual

valve.
FORWARD DELAY VALVE
Forward delay valve is located between EGR CTO switch and EGR
valve. It modifies initial vacuum signal applied to EGR valve by
delaying full vacuum force.
TESTING
EGR VALVE
Valve Opening Test
1) With engine at normal operating temperature and at idle,
rapidly open and close throttle. Open throttle sufficiently to obtain
at least 1500 RPM. Movement should be noticed in EGR diaphragm.
2) If diaphragm does not move, probable causes are: faulty
vacuum signal to EGR, defective EGR diaphragm or defective
backpressure sensor diaphragm (if equipped), or leaks in vacuum lines
or connections.
Valve Closing Test
1) With engine at normal operating temperature and at idle,
manually depress EGR valve diaphragm. RPM should immediately drop,
indicating that EGR valve is not leaking and had been properly cutting
off exhaust gas flow at idle.
2) If there is no change in RPM and engine is idling
properly, exhaust gases are not reaching combustion chamber. Check for
plugged passage between EGR valve and intake manifold.
3) If engine idles poorly and RPM is not greatly affected by
manually moving diaphragm up, EGR valve is not closing off exhaust gas
flow. Check for carbon between pintle, leaking EGR valve gasket or bad
EGR valve.
COOLANT TEMPERATURE OVERRIDE (CTO) SWITCH
NOTE: Engine coolant temperature must be below 100F (38C) to
perform this test.
1) Check vacuum lines for leaks and correct routing.
Disconnect vacuum line at backpressure sensor (if equipped) or at EGR
valve, and attach this line to vacuum gauge.
2) Operate engine at 1500 RPM. No vacuum should be indicated
on gauge. If vacuum is shown, replace CTO switch.
3) Idle engine until coolant temperature exceeds 100
F (38C)
on 4-cylinder engines, or 115F (46C) on 6-cylinder and V8 engines.
4) Raise engine speed to 1500 RPM. Ported vacuum should be
shown on gauge. If not, replace CTO switch.
DUMP VALVE
1) With engine at normal operating temperature, remove dump
valve vacuum hose from manifold and plug manifold connection.
2) Raise engine speed to 2000 RPM. Vacuum should be present
at exhaust ports on bottom of valve. If not, replace valve.
3) Reconnect vacuum hose to manifold and raise engine speed
to 2000 RPM. No vacuum should be felt at exhaust ports on bottom of
valve. If vacuum is present, replace valve.
THERMAL VACUUM SWITCH (TVS)

1) With the air cleaner temperature below 40F (-4C),
disconnect vacuum hoses from TVS and connect vacuum source to large
outlet.
2) Apply vacuum to TVS. TVS should hold vacuum. If not,
replace TVS.
3) Start engine and warm air cleaner to 55
F (13C), or
greater. TVS should not hold vacuum. If it does, replace TVS.

ELE C TR IC AL C O M PO NEN T L O CATO R

1988 J e ep C hero ke e
1988 ELECTRICAL COMPONENT LOCATOR
Jeep Electrical Component Locations
Cherokee, Comanche & Wagoneer
COMPONENT LOCATOR CHARTS









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BUZZERS, RELAYS & TIMERS









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Component Component Location
A/C Clutch Relay On right front wheelwell.

A/C-Heater Blower Relays Under right side of dash, on
evaporator housing.
Automatic Load Leveling Relay On load level compressor
bracket.

B+ Latch Relay On center of right front
wheelwell.
Choke Relay On right front wheelwell.
Door Lock/Unlock Relays Under dash, behind right kick
panel.
Fog Light Relay Behind right headlight, on
wheelwell.

Fuel Pump Relay On right front wheelwell.
Horn Relay Taped to wiring harness, above
fuse block.
Load Swap Relay On front of right front
wheelwell.
Power Antenna Relay Under right side of dash.

Rear Window Defogger Relay Under instrument panel, to
right of steering column.
Rear Wiper Relay In tailgate, next to wiper
motor.
Starter Relay (Graphic 1) Behind right headlight, on
wheelwell.

Starter Relay (Graphic 2) Behind right headlight, on
wheelwell.
Timer Delay Relay Above starter relay, behind
battery.
Trailer Towing Relays,
Brake/Stop Light Relay (Cherokee) Above left rear wheelwell.

Left Turn Signal Relay Above left rear wheelwell.
Right Turn Signal Relay Above left rear wheelwell.








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CIRCUIT PROTECTION DEVICES









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Component Component Location
Circuit Breakers
Power Accessories In fuse block.
Power Window In fuse block.
Trailer Towing Above left rear wheelwell.
Windshield Wiper On side of fuse block.
Fuse Block Under left side of dash.

Fusible Links (Graphic 1) At starter relay.