1996 1500 chevy Z71 ,350 engine. Everything works electronic except when you turn key on it won't crank

Connect it to a code reader scan tool. The engine light codes will tell you some of the reason, but Jeff's answer is far better than mine regarding how all this stuff works..

Glad you solved it.

Are you saying the engine cranks but won't start, or the engine won't crank ?
If the engine does not crank, you would check for voltage at the starter, the neutral safety switch, and the key switch as well as the ground connections.

check for power at the fuel pump if no power check relay's fuses ect If you have power at the pump then most likely bad fuel pump.And yes they do quit just like that

First thing to check is turn your key on and look for a amber light that say check engine. Make sure that light come on and go out after about 3 to 15 sec with the key in on position. If you don't have the light on the most likely your car computer do not get power recheck the fuses and fusible link.

If you have the light on then listen to the fuel pump running when you turn the car on, it should run for about 3 sec. and turn off. If you don't hear the sound of the fuel pump then it would be your fuel pump or relay. obd2 scanner tool

You might have a defective fuel tank pressure sensor!

try locking your car with the key and unlocking it with the key, leave it for 30 second or so between the locking and unlocking , the car thinks some one has tampered with it

i know industry jargon can be confusing, but lets try this. if it turns over but won't start, it could be your ''ignition module'' that sits on top of the vave cover on the motor or it might be the fuel pump or filter. make sure when you crank the engine that the key is all the way turned or it may not always make a proper contact to activate the ignition module. iv'e seen this before & had to change the ignition switch & all worked ok after that. i would need to know engine lt size to give you more details on the matter. please get back to me.

You can't fix it yourself. It takes a scanner at your Local Dealership to do it. People do it, (new battery) everyday unaware that doing so can and usually does, arm the theft system and either kills the radio or the whole car. To me it's just another built-in defect that requires dealer assistance. It's a buzzkill I know, and it probably won't be long until car owners won't even have access to the engine compartment. Sorry.

you said you repl dist cap that means you don't have a crank sensor you have electronic ing module. remove your elec ing module have it tested most auto parts stores could test your module, or check your coil at the neg terminal. should have power. if not you lost your primary volt from your batt.your secondary power is coming from your electronic ing module from the module to the pos terminal on the coil, when the eng cranks,from the coil to the dist cap , from the dist cap center to the rotor then out to the plugs,this all happen pervided the timing belt or timing chain is ok. the cumbustion chainber needs 3 things , thats fuel, air, and spark.