Suzuki XL7 2007 Service Manual page 282

1A-177 Engine General Information and Diagnosis:
– The thermostat is the correct heat range—
Refer to "Thermostat Diagnosis: ".
– Proper engine coolant level—Refer to "Draining
and Filling Cooling System (LY7 GE 47716 Fill):
" "Draining and Filling Cooling System (LY7
Static Fill): ".
2. If the above conditions do not address the symptom,
refer to the additional symptoms tests.
Additional Symptoms Tests
Detonation/Spark Knock: Test the engine for an
overheating condition. Refer to "Engine Overheating:
".
Poor Fuel Economy: Inspect for foreign material
accumulation in the throttle bore, and for carbon
deposits on the throttle plate and shaft. Also inspect
for throttle body tampering.
Rough, Unstable, or Incorrect Idle and Stalling:
Inspect the engine mounts. Refer to "Engine Mount
Inspection: ".
Surges/Chuggles: Test the heated oxygen sensors
(HO2S). The HO2S should respond quickly to a
change in throttle position. If the HO2S do not
respond to different throttle positions, inspect for
contamination from fuel, silicon, or the incorrect use
of RTV sealant. The sensors may have a white
powdery coating and result in a high, but false,
signal voltage, which gives a rich exhaust indication.
The ECM reduces the amount of fuel delivered to the
engine, causing a driveability condition.
Hard Start
• Test the engine coolant temperature (ECT) sensor.
Compare the ECT sensor value to the intake air
temperature (IAT) sensor value on a cold engine. The
ECT and IAT sensor values should be within ± 3°C
(5°F). If the ECT sensor is out of range with the IAT
sensor, test the resistance of the ECT sensor. Refer to
"Temperature Versus Resistance - Engine Coolant
Temperature Sensor" for resistance specifications.
Replace the ECT sensor if the resistance is not within
specification. Refer to "Engine Coolant Temperature
Sensor Replacement: ". If the sensor is within the
specification, test the ECT circuits for a high
resistance.
• Test the fuel pump relay operation. The fuel pump
should turn ON for 2 seconds when the ignition is
turned ON. Refer to "Fuel Pump Electrical Circuit
Diagnosis: ".
Hesitation, Sag, Stumble
• Test the fuel pressure. Refer to "Fuel System
Diagnosis: ".
• Test the generator. Refer to "Symptoms - Engine
Electrical: ". Repair the charging system if the
generator output voltage is less than 9 volts or more
than 16 volts.
Poor Fuel Economy
• Heavy loads being carried or towed
• Acceleration rate too much or too often
• Inspect for foreign material accumulation in the
throttle bore, and for carbon deposits on the throttle
plate and shaft. Also inspect for throttle body
tampering.
Engine Cranks but Does Not Run
Diagnostic Instructions
• Perform the "Diagnostic System Check - Vehicle
Diagnostic Information: " prior to using this diagnostic
procedure.
• Review "Strategy Based Diagnosis: " for an overview
of the diagnostic approach.
• "Diagnostic Procedure Instructions - Vehicle
Diagnostic Information: " provides an overview of
each diagnostic category.
Circuit/System Description
This Engine Cranks but Does Not Run diagnostic is an
organized approach to identify a condition which causes
the engine to crank but not start. This diagnostic directs
the technician to the appropriate system diagnosis.
Diagnostic Aids
Inspect for any of the following conditions:
• The engine control module (ECM) uses the camshaft
position (CMP) sensors to determine engine speed
and position when there is a crankshaft position
(CKP) sensor condition.
• The engine will operate with a CKP sensor condition
only if the ECM has stored the learned reference
position of the camshafts in memory. With a CKP
sensor condition in the signal circuit, the engine will go
into a limp home mode after a hard restart. The ECM
then calculates engine speed from one of the CMP
sensors.
• Insufficient fuel can cause a no start condition.
Thoroughly inspect the fuel delivery system for
sufficient fuel volume to the fuel injectors. Inspect the
fuel supply components for partial blockage or
restrictions.
• Fuel injectors with partially blocked and restricted
nozzles, or a malfunctioning solenoid, can cause a no
start condition. Refer to "Fuel Injector Solenoid Coil
Test: ", "Fuel Injector Balance Test with Special Tool: "
or "Fuel Injector Balance Test with Tech 2: ".