1996 Blazer will not start

Battery clamps. Most likely ground but check both. Air Filter possible staving for air. Get reading from OBT.
might help. If it has one? Is there an idle adjustment?
Check for vacuum line leaks.

PS Also check for the ground cable from engine to frame or body. usually a braided flat unwrapped/uncoated
ground strap, if it has one.
Larry

Does the vehicle start after sitting over night or do you need to jump start it . Is the charge light on ( batt. symbol ) at any time ? Serpentine belt good , tensioner good ? Battery cable connections good an tight and no corrosion ? Battery also good ? That is normal for battery voltage to jump up to 14 volts after starting , alternator is replenishing the battery after starting ,that draws down the battery . Going down to 11 or 12 volts when stopping and almost stalling isn't a charging system problem . You have a idle problem , IAC - idle air control valve or dirty air passage , a vacuum leak . Giving it gas and it going up to 13+ the alternator is working . Your best bet take it to a qualified repair shop and have it check .

I hope you dont have an alarm system as they get triggered, your battery needs charging since its completely dead and boosting would not charge any battery, have your altinator check for out put, should be 14V+

Have you ever put in the gasoline tank any injector cleaner yet because the cleaner will unclog the injectors so full amounts of gasoline can get into the piston chambers the right amounts so try putting injector cleaner into your gas tank. When you put this into the gas tank to remember that it takes time for the cleaner to get to the injectors so you might have to keep trying to start the vehicle many times for the cleaner to unclog the injectors. This will not hurt your vehicle at all so go try this.

Try squirting some starting fluid in the intake and see if it starts if it starts then dies its lacking fuel this could could be that the crank position sensor could be bad. Do you have any codes and have you had them extracted( check engine light is on).the fuel pump may be working and you may be getting fuel up to the fuel rail but if the injectors are not getting the signal to pulsate you will not get any fuel in the intake so check the crank position sensor.Try this first if this doesnt do it check the timing how many miles are on the vehicle if it has high milage it may be in the timing belt. If this has helped you please rate my assistance towards you thank you.

Have you checked the charge on the battery? How bout your connections at the terminals. Vw are very sensitve to voltage drops. You might even have something thats draining your battery

There is some things to check....

(1) Is your alternator charging? take your vehicle to Advanced Autos, Napa or someone like that and have them test your alternator.
(2) Is there something in the vehicle causing excessive drain on the battery when the motor is not running... like is the interior light may be on or something to that affect.
(3) Are you doing enough driving to recharge your battery? short stops and starts is not good for a battery as you may rob more energy from the battery then you are putting back in.
Sounds like something is draining your battery, something must be left on in the vehicle, Advanced Autos or Napa should be able to tell if something is draining your battery when the vehicle is off.

if voltage reulator on alt. does not stop current after battery is charged it will over charge battery abd can drain cell from boiling electrolite out.check 4 bulged battery case(swelling) indication of overchaeging.the start problem could be your starter wires connection.remove starter wires clean contacts and torque respectively.dont forget the ground to motor.sounds like a loose or corroded contact somewhere.

Its most likely the voltage regulator which is most often attached or inside the alternator its a replacable item. Normaly the sighns of an alternator gone are a dying battery.

bad ground cable,use a jumper cable from negative to alternator bracket, if it starts thats it.