Help! (or, Can You Assist Please My Car Won't Start)

The complaint was the car stalled on a trip and would not restart. The car was towed over the weekend and setting in the lot to welcome me on Monday morning. I gave it a quick look to see that it was safe to try and crank the engine. It is always better to see that half the engine isn't taken apart or similar while others before you were trying to get the car running. It looked safe to try and crank the engine.
Let me take a moment here to make note of "will not start" complaints. In diagnosing a problem what you are really doing is narrowing the possibilities down to the actual cause. When I turned the key to start position there was no starter engagement. The complaint just went from "will not start" to "will not crank". Engine *cranking* is the starter engaging and turning the engine. Focus was now on why would the engine not crank.
Clues were that the instrument cluster lights were flickering, gauges were erratic and no headlight operation when the light switch was turned on. Those things could be from a discharged battery. If you are not familiar with a "booster pack" it is a sort of portable battery with attached cables. You can connect the cables directly to the car and power the electrical system with a "known good" battery without a lot of trouble. 

With the booster pack connected the lights work, the gauges work, the door chime and interior lights come on AND the engine will crank. The engine will also start and run. The diagnostic problem had just shifted again. I was now looking for why the battery was dead. The next clue was the battery light on the instrument cluster. The red battery light was on with the engine running.  A battery light usually indicates an alternator that isn't working. I checked the system voltage at the booster with a voltmeter and since the voltage was the same with the engine running as it was when not running it also indicated an alternator that wasn't working. 

Ideally I wanted a fully charged battery before doing some charging system tests but the battery was not accepting a charge after quite some time on the charger. The actual battery on this car is inside the fender on the driver's side. It is not readily accessible. I could attach the booster pack and do some charging system checks using that as a battery. An extremely discharged battery can take an overnight on the charger to reach full charge and this one looked like it was going to do just that. I could see through to the battery from the engine compartment and the battery looked new, with good clean connections. I decided to go ahead and test the charging system using booster pack as the power source. 

Since I wasn't seeing charging from the alternator I started by testing for voltage at the alternator. I had power at the output post (large wire). There is a connector with 2 small wires at the alternator. The brown w/gray stripe should have power when the car is running and the computer is trying to energize the field circuit. I had power there as well. The alternator should have been charging, but wasn't. I needed to let the battery charge overnight and get an okay from the car owner to replace the alternator. 

The problem went from no-start to bad alternator step by diagnostic step. 

Thanks for reading!

Kenneth Hayes

G&G Auto Repair