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. In order for the engine to start and run, the correct amount of good quality fuel must be properly delivered to each cylinder. The timing of the valve train operation in relation to piston position is also critical, as is mechanical compression of the air/fuel mixture.
The Engine Cranks but Does Not Run diagnostic table assumes the following:
| • | The battery is completely charged. Refer to Battery Inspection/Test in Engine Electrical. |
| • | The engine cranking speed is acceptable. Refer to Engine Cranks Slowly in Engine Electrical. |
| • | There is adequate fuel in the fuel tank. |
Diagnostic Aids
Inspect for any of the following conditions:
| • | 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 and Fuel Injector Balance Test with Special Tool . |
| • | There may be fuel spray at the fuel injectors and the indicated fuel pressure may be correct, yet there may not be enough fuel to start the engine. If the fuel injectors and the injector circuit are OK, and fuel spray is detected, the fuel injector ON time may be inadequate. If the engine control module (ECM) receives incorrect inputs from the various information sensors, the fuel delivered by the fuel injectors may be inadequate to start the engine. Check all the engine data parameters with a scan tool and compare the values indicated with the expected values or the values from a known good vehicle. |
| • | Check the crankshaft position (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 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. |
| • | Inspect the engine for good secure electrical grounds. Refer to Engine Controls Schematics . |
| • | If the engine almost starts and then stalls, check for an open in the ground circuits of the CKP sensor and the camshaft position sensor. |
| • | Water or foreign material in the fuel can cause a no start or engine will not stay running condition. During freezing weather water can freeze inside the fuel system. The engine may start after 30 minutes in a heated repair shop. The malfunction may not recur until parked overnight in freezing temperatures. Extreme weather conditions can cause contaminated fuel to prevent the vehicle from starting. |
| • | A vehicle that starts and runs after being brought to the repair shop for a no start condition, may have an ignition system that is susceptible to moisture. Spray water on the ignition system components and the wiring in order to check for an engine starting or will not stay running concern. |
An intermittent malfunction may be caused by fault in any of the critical information or component electrical circuits. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .
Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The listed DTCs can cause a no start. If a DTC is set, diagnose the DTC before using this diagnostic procedure.
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This step tests for the correct operation of the CKP sensor. If there is a condition with the CKP sensor or circuits, engine speed will not be displayed on the scan tool. Depending on the circuit failure, DTC P0337 may not set.
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The voltage to the ignition coil is controlled by the fuel pump relay. This step tests for the correct operation of the fuel pump relay.
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It is important to test for the presence of spark from all of the ignition wires.
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This step tests for proper operation of the ECM control of the fuel pump circuit.
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The voltage to the fuel injectors are controlled by the ignition relay. This step tests for the correct operation of the ignition relay.
Step | Action | Values | Yes | No | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connect End View Reference: Engine Controls Connector End Views | ||||||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||||||||||||||||
Does the scan tool display DTC P0118, P0201, P0202, P0203, P0204, P0336, P0337, P0351, P0352, P0601, P0602, or P0607 failed this ignition? | -- | Go to Step 3 | ||||||||||||||||||||
Is engine speed displayed on the scan tool? | -- | Go to Step 4 | Go to DTC P0327 | |||||||||||||||||||
Important: Perform this procedure on both sides of the fuse when the fuel pump relay is commanded ON. Does the test lamp illuminate on at least one side of the fuse when the fuel pump relay is commanded ON? | -- | Go to Step 5 | ||||||||||||||||||||
Does the spark tester spark and is the spark consistent? | -- | Go to Step 6 | ||||||||||||||||||||
Command the fuel pump ON, with a scan tool. Does the fuel pump turn ON? | -- | Go to Step 7 | ||||||||||||||||||||
Does the test lamp illuminate on at least one side of the fuse? | -- | Go to Step 8 | ||||||||||||||||||||
8 |
Caution: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete. Is the fuel pressure within the specified range while the fuel pump is operating? | 380-427 kPa (55-62 psi) | Go to Step 9 | Go to Fuel System Diagnosis | ||||||||||||||||||
9 | Inspect for the following conditions:
Did you complete the action? | -- | Go to Step 10 | -- | ||||||||||||||||||
10 |
Does the engine start and continue to operate? | -- | Go to Step 11 | Go to Step 2 | ||||||||||||||||||
11 |
Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||||||
