Engine Cranks but Does Not Run

Engine Cranks but Does Not Run

Description

The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic table directs the service technician to the appropriate system diagnosis.

The Engine Cranks but Does Not Run diagnostic table assumes the following:

* The battery is completely charged. Refer to Battery Inspection/Test Battery Inspection/Test in Engine Electrical.
* The cranking speed is within specifications. Refer to Engine Cranks Slowly Engine Cranks Slowly in Engine Electrical.
* There is adequate fuel in the fuel tanks.

Diagnostic Aids

Inspect for the following conditions:

* Mass air flow is compared to a calculated mass air flow based upon the manifold absolute pressure (MAP), throttle position (TP), and engine RPM readings. A skewed or unresponsive MAP sensor at KEY ON will cause the predicted air flow value to be inaccurate. Compare MAP and TP sensor values to that of a known good vehicle.
* Faulty engine coolant temperature (ECT) sensor. Using a scan tool, compare engine coolant temperature with intake air temperature (IAT) on a completely cool engine. Engine coolant temperature should be within 3°C (5°F) of the intake air temperature.
For an intermittent condition, refer to Intermittent Conditions Intermittent Conditions.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
3. This step determines if the ignition relay is providing the listed circuit breakers with voltage.
5. This step determines if the fuel pump is operating electrically.