When there is a problem starting the vehicle, the question most mechanics attempt to answer first, is the problem with the fuel or ignition system. Basic troubleshooting should begin by determining "is there spark'' and "is there fuel''- Quite often it is easier, especially on fuel injected vehicles, to begin by verifying if the ignition system is properly functioning. The NO-START test provided in this section will only verify whether is an adequate spark supply to each cylinder. For complete ignition system diagnosis and testing, please refer to the detailed information covering engine electrical components and ignition systems found earlier in this information. If the ignition system checks out (there is spark), then you must determine if the fuel system is operating properly (is there fuel-).
- Connect a voltmeter across the battery terminals. If battery voltage is not at least 12 volts, charge and test the battery before proceeding.
Turn the key to the
position, and observe the voltmeter. If the engine turned over and battery voltage remained above 9.6 volts, go to the next step. If the engine failed to crank and/or voltage was below 9.6 volts, proceed as follows:
If the instrument panel lights dim, load test the battery, check the battery terminals and cables, test the starter motor, and verify that the engine turns.
Using a spark tester as described in
, check for spark at two or more spark plugs.
If a normal spark is observed, continue testing following the appropriate fuel system diagnostic procedures.
See Figure 1
- Remove the air cleaner assembly.
Operate the accelerator pump, while watching for fuel discharge from the port in the throttle barrel. If fuel is not discharged from the pump, proceed to next step. If accelerator pump operates, refer to the appropriate section and check the following items:
Remove spark plugs and verify the engine is not flooded.
- Verify adequate fuel in the tank. If okay inspect visually inspect the fuel supply system components. Check for damaged lines, clogged fuel filter, etc.; if okay proceed to the next step.
Most fuel pressure specifications are given at idle speed. It may be necessary to compensate the reading obtained; verify that adequate pressure exists to unseat the float and fill the carburetor.
- Connect a fuel pressure gauge and check fuel pressure and volume. If fuel pressure and/or volume is not within specifications, replace the fuel pump and retest.
FUEL INJECTED ENGINES
See Figures 2, 3, 4 and 5
Cycle the ignition switch
, several times, while listening for fuel pump operation.
If fuel pump operates, proceed to next step.
Verify adequate fuel in the tank, then connect a fuel pressure gauge and check fuel pressure.
If fuel pressure is within specifications, proceed to next step.
Disconnect the fuel injector connector and connect a noid light to the wiring harness. Crank the engine, while watching the light. Perform this test on at least two injectors before proceeding.
If the light does not flash, go to the next step.
Check and verify the MIL lamp is operating properly.
If the light does not operate, check the ECM and related wiring.
- Check the engine valve timing and overall mechanical condition of the engine. If okay, items such as; poor fuel quality, faulty injectors and computer controlled devices should be checked. Although these items are less likely, a shorted TPS or faulty coolant temperature sensor, are also possible causes of a no-start condition.