When your engine cranks but fails to start, it could be because of no spark.
No spark is one of the most common reasons and why I like to start here.
Confirm Your Engine Has No Spark.
No Spark Testing – Disable the fuel system by removing the fuel pump fuse or relay.
No Spark Testing – Insert a spark plug tester into the plug boot and ground it on a piece of metal on the engine.
Finally, Have someone crank the engine and watch for no spark.
If the engine has a coil-on-plug ignition system with no plug wires:
- Remove one of the coils from the spark plug.
- Use an extra spark plug.
- A spark plug tester.
- Or even a screwdriver in the end of the coil.
Ground it on a piece of metal on the engine.
Finally, Have someone crank the engine and watch for a spark.
No spark indicates an ignition problem.
In extreme cases the PCM may have failed.
In some cases, a PCM problem will cause the vehicle not to run at all.
The PCM’s functions include positioning the crankshaft and controlling the ignition spark and timing.
If there are problems with how the PCM performs these functions, the vehicle may not run.
So, your engine cranks normally but will not start because it has no spark.
The No Start Problem May Be Due To Any Of The Following:
A Bad Crankshaft Position (CKP) Sensor (on engines that do not have a distributor).
- First of all, look for any broken, loose or corroded wires from the sensor to the PCM. The crankshaft position (CKP) sensor monitors the position or rotational speed of the crankshaft. If the crankshaft position sensor has failed completely, and isn’t sending a signal to the ECU at all, then the computer won’t send any fuel to the injectors. This will leave you unable to start the car.
A Bad Ignition Module (on engines that have a distributor or use an ignition module separate from the PCM).
- Ignition modules are solid state switching devices that typically use a component like a transistor to switch the current flow through the primary winding of an ignition coil on and off. In that way, an ignition module works a lot like mechanical points. However, ignition modules are not able to do the job alone. Whereas points were mechanically operated by the rotation of the distributor shaft, an ignition module requires some type of external input in order to activate.
- If your vehicle stalls unexpectedly during operation and will not start again, it is likely because of loose or corroded electrical connections in the ignition module. In this case, check the switch, clean oxidized terminals, and replace broken wires if necessary. Another problem is damage by overheating. If you cannot start the car, you need to test the ignition control module.
A Bad Pickup Inside The Distributor (on engines that have a distributor), A Stripped Distributor Drive Gear (common problem with plastic distributor drive gears), Broken, Loose Or Corroded Wires From The Pickup To The Ignition Module Or PCM.
- Electronic ignition pickups are a component found on traditional electronic distributor ignition systems. They are located inside the distributor and function as the trigger for the ignition system to produce spark. The pickup coil monitors the rotation of the distributor and triggers the ignition system. Consequently, at the optimal moment to produce the best timed spark for best engine performance. As the ignition pickup essentially functions as the activation switch for the entire ignition system, when it fails, it can greatly affect the operation of the vehicle.
- One of the first symptoms of a bad ignition pickup is an engine that stalls and eventually will not restart. Consequently, An old or failing ignition pickup may cut out signal intermittently, which may cause the engine to stall. The engine may suddenly just shut off, almost as if the key had been turned off. Depending on the nature of the issue, sometimes the vehicle can be restarted and driven. Consequently this problem will only get worse and completely fail.
A Bad Ignition Coil (on engines that have a distributor and a single coil).
- The ignition coil is the unit that takes your relatively weak battery power and turns it into a powerful spark. One of the most common symptoms of a faulty ignition coil is when the vehicle runs for a while and then the car’s engine suddenly dies for no apparent reason. As a result, This occurs after the ignition coil or module gets too hot. Furthermore, it could correct itself after the engine module cools. In some cases, a bad ignition coil will result in the vehicle not starting it all.
A Bad Rotor Or Distributor Cap (cracks or carbon tracks that are allowing the spark to short to ground).
- Often the distributor cap is suspect. The internal and external surface of the cap should be clean. No erosion should be on the surface and the firing points should be free of rust or corrosion. The rotor needs to be checked as well. Consequently, It could short out the coil voltage and cause a faulty connection inside the terminal of the distributor cap. The result is a misfire in the spark plugs. Look for any cracks or carbon trace in the cap.
Faulty Ignition Switch.
Normally, when you put the key in the ignition switch and turn it, you will have three positions:
- The first position is the ‘off’ status.
- The second position is the ‘on’ position where the dashboard lights come on but your engine will still be off.
- The third position is the ‘start’ mode where you exert key pressure to actually fire the engine up.
One major sign of a bad ignition switch is the instrument panel not lighting up in position two.
Suspect the ECM as a last resort. Therefore, If all other components are functioning properly you may have a bad ECM. At this point you should consider taking your vehicle to a professional to diagnose the problem.
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