Q: Car turns over but won't start.

asked by on May 12, 2016

My engine fails to start. It turns over, and I hear scattered, weak pops. There's some kind of combustion happening, but it won't crank. When I pulled the plugs, I got a spark, but it was very weak. The plugs themselves didn't look good; they were fouled up and the electrode was eaten away. It doesn't look like anyone has changed them in over 100,000 miles.

The plugs have been replaced, but the spark is still very weak, not bright blue like I would expect. I don't see any plug wires. I have a resistor pack and rubber boots together in one pack on top of the engine. Is there way to test if the that pack delivers proper voltage?

As far as the fuel system, my fuel pump activates, and I still have some pressure, as the fuel port in the injector squirts when I use a screwdriver. The check engine light stays on when the motor is being cranked. I don't know if it was lit up before. As far as I know, the light should go away once the engine is running. The crank sensor should turn it off. The computer isn't throwing any codes, and there were none saved. All systems check out when I hook up my reader. I suspect the crank sensor or wiring may be bad. Is there anything else that could cause this?

I think that the ignition coil is a very likely cause of this issue. Since the spark plugs do not have their own individual coils, if the main ignition coil fails, it could affect all cylinders’ ability to spark.

This part is also a fairly common failure on this engine. To be honest, this is somewhat of a poor design of ignition system due to the probability of failure and the problems that can be associated with just one part failing. General Motors offers a diagnostic test for this ignition coil using either a GM scan tool or a digital multimeter.

For best results, have the ignition coil tested by a certified mechanic to ensure that the readings are accurate and comprehended correctly. Once the coil has been tested, the mechanic would relay the results of the test over to you to make a repair decision, which may include replacing the ignition coil, if deemed necessary.

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