2002 Gmc Safari 4.3L, ticking/clicking sound coming from area by alternator and vehicle would not start after being turned on and off a few times. Dealer claims it is distributor cap and rotor plus weak battery with dead cell that appears to looking in good condition. Please advise.

Try charging the Battery first or if you have a second car and a booster cable, Try jump starting the battery. A simple week battery will not have enough power to turn the engine or activate the ECM to start the ignition system. AS the starter draws power from the battery, the voltage drops. If the voltage drops less then 10.5 volts, the ECM shuts down the ignition system. Start with addressing the battery first, most battery last only 4 to 5 years the most and yours may just be at the end of it's life time. Good luck and keep me posted.

Usually a dead cell will show normal to low voltage on a voltmeter but it won't allow the car to start. I'm not sure on the electrical mechanics of it, but it has something to do with the battery not being able to run a return current through the starter when you're trying to start it. If the car will start up fine with jumper cables then the battery is most likely dead.