Checks
| Action
|
DEFINITION: The engine cranks OK, but does not start for a long time.
The engine does eventually run, or the engine may start but immediately stalls.
|
Preliminary Checks
| Refer to
Powertrain On Board Diagnostic (OBD) System Check
.
| • | Check that the driver is using the correct starting procedure. |
|
Sensor Checks
|
| • | Check the engine coolant temperature (ECT) sensor. Use a scan
tool in order to compare the engine coolant temperature reading on a cold
engine with the ambient air temperature reading of the same engine. A coolant
temperature reading that is more than 5°C (41°F) different than
the ambient air temperature reading (on a cold engine) may indicate a high
resistance in the coolant sensor circuit or the sensor itself. Refer to Temperature vs Resistance
. |
| • | Check the throttle position (TP) sensor. A sticking throttle shaft
or a binding throttle linkage will causes a high TP sensor voltage (open throttle
indication). The PCM may not control the idle if a high TP voltage is present.
Monitor the TP sensor voltage with the scan tool or a voltmeter. The indicated
voltage should be less than 1.25 volts with throttle closed. |
| • | Check the CKP sensor engine reference signal with a scan tool.
Observe the Engine Speed parameter while cranking the engine. The scan tool
should indicate a steady 200-300 RPM while cranking. If the
erratic values, such as sudden spikes in engine speed are displayed, the
engine reference signal is not stable enough for the engine to start and
run properly. Check for a short to ground in the CKP sensor Ignition Reference
Low circuit . A short to ground in the CKP sensor Ignition Reference Low
circuit will cause a faulty engine reference signal to be sent to the PCM,
but will not set a CKP sensor DTC (P0335). |
|
Fuel System Checks
|
| • | Check the operation of the fuel pump check valve. A faulty in-tank
fuel pump check valve will allow the fuel in the fuel lines to drain back
to the fuel tank after stopping the engine. This condition can cause hard
starts, especially on hot soak restarts. In order to check for this condition
perform the fuel pressure check in
Fuel System Diagnosis
. |
|
Ignition System Checks
|
| • | Check for adequate secondary ignition voltage with a J 26792
spark tester or an equivalent. |
| • | Check the spark plugs for any of the following conditions: |
| - | Wet (fuel fouled) plugs. |
| - | A terminal screw that is bent or loose (rotate and pull). |
| - | A ceramic insulator that has cracks, carbon tracking or deposits
(red or black dust) |
| - | A tip insulator that has cracks, carbon tracking, deposits (oil,
carbon, glazing, fuel additive), or is loose (rattles). |
| - | A center electrode that is loose (wiggles side to side) |
| - | An incorrect spark plug gap that is too large or too small. |
| • | Check for bare or shorted ignition wires. |
| • | Check for loose ignition coil connections. |
| • | Check all the ignition system electrical connections. |
|
Additional Checks
|
| • | Check the IAC system for proper operation. |
| • | Check for no crank signal to the PCM. In order to provide improved
cold engine starting, the PCM delivers a richer fuel injector pulse on a cold
engine when the crank signal is present. Observe the Starter Switch parameter
on the scan tool while cranking the engine. A faulty crank signal circuit
WILL NOT cause a no start, only a longer start time under harsh conditions. |
| • | Check for Service Bulletin updates or information. |
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