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
Diagnostic System Check - Engine Controls
.
• | Check that the driver is using the correct starting procedure. |
|
Sensor Checks
|
• | Inspect for a shifted or fixed engine coolant temperature (ECT)
sensor. Test 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 (9°F)
different than the ambient air temperature reading on a cold engine
may indicate a high resistance in the coolant sensor circuit or
in the sensor. Refer to
Temperature Versus Resistance
. |
• | Check the throttle position (TP) sensor. A sticking throttle shaft
or a binding throttle linkage will causes a high TP sensor voltage or an 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 digital multimeter. The indicated voltage should be less
than 1.25 volts with the throttle closed. |
• | Check the canshaft position (CMP) 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 erratic values, such as sudden spikes in the
engine speed, are displayed, the engine reference signal is not
stable enough for the engine to start and run properly. |
|
Fuel System Checks
|
• | Check the operation of the fuel pump check valve. A faulty check
valve will allow the fuel in the fuel lines to drain back into 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 loose ignition coil connections. |
• | Check all the ignition system electrical connections. |
|
Additional Checks
|
• | Inspect the PCM grounds and engine grounds for clean and tight
connections in the correct locations. Refer to
Engine Controls Schematics
. |
• | 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. |
|