Tech Stuff

Quick no-start diagnosis

A simple spark tester goes a long way in confirming that the ignition system is not the cause of your no-start.
<p>A simple spark tester goes a long way in confirming that the ignition system is not the cause of your no-start.</p>

About the author: Truglia is the owner of Car Clinic, a state-of-the-art repair facility in Mahopac, N.Y. He is ASE certified with a M.A. from Columbia University. In the automotive world he has been trained by Technicians Service Training and Automotive Technician Training Services. Car Clinic’s facility is fully equipped with factory-level equipment and services American, European and Asian vehicles, including diesels and hybrids. (All vehicles were diagnosed by G. “Jerry” Truglia, Alex Portillo and Craig Truglia.)

Don’t let those no-starts frustrate you. Unlike intermittent faults we have to wait for, the no-start is ever-present and can be isolated in about five minutes. Once we can figure out our diagnostic direction, then we can nitpick exactly what’s wrong with the vehicle.

Sparks, fuel, mechanical

Engines need three things to run. Spark ignites the fuel and if anything from the spark plug to the PCM that grounds the coil is bad, the car will not move. Fuel is needed for the controlled explosions of engine combustion to take place. So, anything from the fuel injectors to the fuel pump to the PCM may prevent fuel from getting to the engine and allowing combustion to take place. Lastly, you need a good working engine! Bad timing (jumped timing belt/chain), low compression (washed down cylinder walls), or high exhaust back pressure (clogged catalytic converter) can prevent an engine from working properly.

Now, why does my subject header list spark first, then fuel, and lastly mechanical? This is because in the real world a no-start is usually caused by the same parts that cause misfires. Sure, bad engine compression can cause a misfire, but how many more times does the correct repair involve replacing spark plugs or the ignition coil? The same applies to no-starts. Look at the most likely culprits and then work your way down the list.

Tags: Alternators  Battery 
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