When Your Car Won't Start (2005 Impala)

There are definite differences to how a car owner sees a no-start versus how a professional mechanic sees it. One thing is that if your car won't start you will try to make it start. There is no good time for your car to not start. You were on your way somewhere and your car was needed to take you there. If trying a dozen times while crossing your fingers might work, you'll try it.
A mechanic, on the other hand, isn't necessarily trying to start your car. He's trying to see why it won't start. There is a difference. There are a lot of reasons for a car to not start and there are a lot of different cars. Lets walk through this particular no-start on a 2005 Impala.
No-start has to get broken down into smaller possibilities. Does the engine crank? Cranking is the starter engaging and spinning the engine. If it cranks well, spins over well then your no-start isn't a battery, alternator or starter issue and you can forget about looking for jumper cables.

I noticed there was no check engine (MIL) light on with the key on. There should be at least a bulb check. I connected a scan tool mainly to see if the engine computer was working. The computer was communicating, several codes were stored but none seemed directly related to the no-start. There were a LOT of misfires in history for #6 cylinder and quite a few for #3 as well. Also, the scan data showed the computer was commanding the MIL on. Bulb out? The interesting thing about those misfires was that #3 and #6 are on the same ignition coil. There are 3 ignition coils bolted to the ignition module and 2 cyls fire from each coil. The misfires as seen here are usually a bad ignition coil due to worn spark plugs. As I said, it doesn't seem directly related to the no-start but could very well have brought about the problem. The car has 306,000 miles. I wonder what the spark plugs look like.

Okay, the car cranks but does not start. The MIL does not come on but the engine computer is alive. When the car was last running it was misfiring on two cylinders and very likely has worn spark plugs and a bad ignition coil. Of course spark plug wires would also be part of that running problem. But the ignition problems on that side would make the car run bad, not keep it from starting.

I could hear the fuel pump run and a gauge showed good fuel pressure to the rail. So primary fuel delivery was good.

Secondary fuel delivery is the injector spray into the cylinder and I have no problem with using a noid light to check the injector signal. If it doesn't flash while cranking I'm getting no injector pulse.

I wanted to test ignition spark at the spark plug end of the plug wires, maybe even remove #3 to see just how badly these were worn. However those plug boots were stuck to the spark plugs. Not a single one was coming off without doing some damage. For the time being I ran a good wire from one coil tower over to a spark tester and no there was no spark while cranking. The items missing from a successful start are secondary ignition and injector pulse signal.

Now when I see no spark and no injector signal I start thinking there is a problem with a crankshaft position signal. Throw in that the plugs, wires and coil have problems and we could even have a bad ignition module as well. I watched the tachometer while cranking and it never moved feeding right into my hypothesis.

I decided to check my signal from the crankshaft position sensor which is behind the front crank pulley. Removing the right front tire will give pretty good access for testing purposes. The wiring was not in good shape near the connector for running the car, but those bare spots were good for connecting test leads. With the key on and turning the crankshaft by hand I should be able to see the crank signals from the sensor but there were no signals. I need voltage to the sensor from the ignition module to make the sensor work but there was no voltage from the module.

I had ignition voltage to the module but nothing from the module to the crank sensor. I had a bad ignition module. Fits right in with the way a secondary will die if you keep driving with an ignition misfire, plugs, wires, coil, module. My car won't start had become I have a bad ignition module that isn't providing voltage to my crankshaft position sensor and that my friend, is something you can work with.

On removing the old module I found there was a crack in the 1-4 coil. Two bad coils in total (of 3). One bad ignition module. Replaced spark plugs and plug wires and repaired wiring at sensor.

It's about patience and a logical plan.

Kenny@ggauto.repair
G&G Auto Repair
Searcy