Diagnostic Instructions
Circuit/System Description
The engine cranks but does not run 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.
This diagnostic assumes the system voltage levels are adequate for starter motor operation. Fuel level and fuel quality must be determined for correct diagnosis.
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 LINK (Fuel Injector Diagnosis). |
• | 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 vehicle in good condition. |
• | Check the crankshaft position 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. |
• | If the engine almost starts and then stalls, check for an open in the ground circuits of the crankshaft position sensor and the camshaft position sensor - Intake or camshaft position sensor - Exhaust. |
• | 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 min 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. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
• | EL-26792 HEI Spark Tester
|
• | CH-48027 Digital Pressure Gage
|
For equivalent regional tools, refer to
Special Tools.
Circuit/System Verification
Attempt to start the engine. The engine should start and run.
Circuit/System Testing
- Crank the engine for up to 15 s.
- Observe the vehicle DTC information with a scan tool.
⇒ | If any of the following DTCs are set, refer to
Diagnostic Trouble Code (DTC) List - Vehicle to diagnose those DTCs P0201-P0204 00, P026 00, P0262 00, P0264 00, P0265 00,
P0267 00, P0268 00, P0270 00, P0271 00, P0335 00, P0336 00, P0601 00, P0602 00, P0604 00, P0606 00, P0607 00, P0686 00, P0687 00, P0689 00, P2610 00. |
- Ignition OFF for 90 s, determine the current vehicle testing altitude. Ignition ON, observe the scan tool MAP Sensor parameter. Compare the parameter to the
Altitude Versus Barometric Pressure table.
The MAP Sensor Pressure parameter should be within the specified range indicated in the table.
⇒ | If the reading is not correct for your altitude, diagnose the B74 Manifold Absolute Pressure (MAP) Sensor. Refer to LINK (DTC P0107, 00 or P0108 00). |
- Verify the following scan tool parameters indicate Not Run to OK, when the engine is cranked:
⇒ | Cylinder 1-4 injector circuit short to volts test status |
⇒ | If the parameters do not indicate the specified values, refer to
DTC P0201, P0202, P0203, P0204, P0261, P0262, P0264, P0265, P0267, P0268, P0270, or P0271. |
- Observe the engine speed parameter while cranking the engine.
- Install a
EL-26792 HEI Spark Tester
.
- Crank the engine for 15 s. Spark should be observed from the
EL-26792 HEI Spark Tester
.
- With the ignition ON and the engine OFF, test the fuses that are supplied by the ignition main relay for voltage. The test lamp should illuminate at each test point for the following fuses:
⇒ | If the test lamp does not illuminate on at least one side of each fuse, refer to LINK. |
Note: Additional DTCs may set when using the fuel pump output control.
- Command the fuel pump ON and OFF. Fuel pump should energize when commanded ON and De-energize when commanded OFF.
- Turn OFF the ignition.
- Install the
CH-48027 Digital Pressure Gage
or
CH-48027 Digital Pressure Gage
. Turn ON the ignition and command
the fuel pump ON while observing the
CH-48027 Digital Pressure Gage
or
CH-48027 Digital Pressure Gage
. The fuel pressure
should be between 384-425 kPa (56-62 PSI).
- Inspect for the following conditions:
• | Compare the actual engine coolant temperature to the ECT parameter. |
• | Air filter and air intake system for restrictions and obstructions |
Repair Verification
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Spark Plug Replacement.