Spark plug must be grounded against the engine to be checked. If it is truly a no/spark condition, then the next thing to check is the “dead-man” switch if it is on a pushmower and then check the ignition module air-gap. That is the distance in between the legs of the coil and the magnets in the flywheel. Different engine applications (you did not say) are set a few thousandths different but a good rule of thumb is closer is better. Set the air gap at .008″-012″ or about the thickness of a standard sized business card. If this doesn’t produce a spark, then the ignition module is possibly bad.
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What Can Cause a No-Crank, No-Start Situation? If your car does not start and does not crank, there`s likely an issue with the starter or the charging system, which includes the battery, the battery terminals, the alternator, and any wire connections.
There are a number of possible causes for a lifeless mower, but ultimately only two things are required for an engine to start: fuel and a spark. If the engine isn`t getting a spark at the plug or fuel isn`t reaching the engine, your lawn mower is never going to start.
If no spark appears, check for broken wires, shorts, grounds or a defective stop switch. Once you have confirmed that the stop switch is working, reconnect the spark plug lead.
With a poor ground the starter ring return path may not allow adequate amps to return to allow a starter to reach the torque and speed to start. Normally, however, with a well tuned car and cranking, the engine will fire right up. Weakness, though, and it may not start.
A Bad Crankshaft Position Sensor
The crankshaft position sensor monitors the position and rotational speeds of the crankshaft. Without the crank sensor, the engine control module (ECM) wouldn`t know when to fire the fuel injectors and ignite the spark plugs.
The starter will not have any impact on the engine`s ability to produce spark. There are a number of issues that may cause an ignition system to not produce spark. A bad crankshaft position (CKP) sensor (on engines that do not have a distributor), or broken, loose or corroded wires from the sensor to the PCM.
There are diesel engine which run without any spark plug. They have higher compression ratio so a significant amount heat is generated at the end of compression stroke and only spray is needed for blast.
If you do not see a spark, there is an ignition problem. Remove a plug wire and insert an old spark plug or a spark plug tester into the end of the wire (the plug boot). Place the spark plug on a metal surface on the engine, or ground the spark plug tester to the engine. Then crank the engine to check for a spark.
Incorrect timing is the most overlooked and misdiagnosed cause of a no-start. Perhaps you automatically think of ignition timing as the position of the crankshaft when the No. 1 plug fires. While this is important, it isn`t the only timing condition that can influence a no-start.
Symptoms of An Electrical Ground Fault
However, a few common symptoms of electrical ground faults are: Strobing lines on your TV or desktop computer monitor. Humming or buzzing in your home stereo or TV audio system. Unexpected shocks when you touch metal appliances, trim, or pipes.
If the ignition relay shorts, burns out, or otherwise fails while the engine is operating it will cut off power to the fuel pump and ignition system. This will cause the vehicle to immediately stall due to fuel and spark being cut off.
A Bad Crankshaft Position (CKP) Sensor
If the crankshaft position sensor has failed completely, it will not send 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.
Why won`t my car start but I have power? If you attempt to start up your car but the engine won`t turn over and the dashboard lights up, then you most likely have an issue with your battery. You could have a damaged or corroded battery terminal, which is stopping the engine from starting up when you fully turn the key.