It cranks, but why doesn't it start?

Hi Anthony......,It's either electrical OR fuel so If you're a hands on guy then do this.... Pull a spark plug lead off a spark plug OR if it's a "COIL ON A SPARK PLUG" pull that off and put a spare spark plug into that spark plug lead OR coil, Then earth that spark plug to a clean part of the motor(make sure the spark plug is touching steel)Turn motor with the key and see if the spark plug sparks.... If it sparks then you have a fuel problem....... But if no spark then you have an electrical problem.... The links below are YouTube videos showing how to fix a car that doesn't start/cranks but doesn't start, Also there's videos down the right side of the links that may help as well...................
Fixing Car That Does Nothing When You Turn The Key

Fixing Car That Cranks But Doesn Start Up

Car Cranks But Will Not Start

No the ignition switch doesn,t have any thing to do with the car not get spark,Who ever told you that clearly has no clue what they are talking about, It probally has to do with the coil packs,Or the (PCM) might evan have to do with it,Being that it is a (Audi) The best thing to do is to take it to some body that works on (Audi,s) End now,s what there doing, Then ,Waste your money, Paying some mechanic that has never work on one, End doesn,t have a clue about them,

Before you threw a bunch of parts at it maybe you should at least see if it has spark. If it doesn't have spark then the crank sensor and coil pack would be appropriate. If it is not getting fuel then the fuel pump, filter, etc. would be the way to go. So see if there is spark, do this by pulling a spark plug and see if there is spark out the end with it plugged into the wire and cranking it over. If there is spark put all this back together and squirt some fuel into the throttle body while cranking it over, if it tries to start but doesn't try to start on its own without squirting fuel in it then the fuel pump is bad. How many miles on it? Possibly the cam timing is off. Maybe take a compression check and see if the cam is out of time.

Check for spark and gas. Try to add gas to the intake. If it starts, there is a fuel delivery problem. If it doesn't, then there may be no spark which you can test using a spark tester.
If there is no spark, the crank sensor circuit may be at fault.

you need fuel, compressen, and electrical , make sure you all of the above dose it make any noise like it is trying to start ?

It's very likely your fuel pump has failed. Have somebody thump on the fuel tank while you're cranking the engine and see if it starts. If it does, replace the fuel pump. Otherwise get your fuel pressure checked, and check for spark. If no spark, check to make sure the distributor is turning(if applicable) If a 3.3 motor with no spark, suspect the crank sensor or cam sensor. Crank sensor is much easier to replace if experimenting.

O2 sensor won't cause a no spark no start condition but the crank sensor will. most time bad crank sensor will not set a code if engine doesn't start. usually set code on o drop while driving. I would check connection at sensor if good then replace sensor.

No this does not affect the fuel pump. It will affect the spark though. Hit the gas tank in the center a few times. If it starts then replace the fuel pump. Unfortunetly pumps with a few yaers on them will die when ran out of gas. If it doesn't start pull one of the spark plug wires, insert a screwdriver and put it close to the engine. crank the engine and watch for a spark. if there is no spark then replace the crank shaft sensor. before you replace the fuel pump.

check your crank sensor, if bad it will crank but computer doesn't see it so it shuts down fuel and spark

IF the car cranks over but doesn't start you need to see if you have Spark and Fuel. IF it doesn't crank, check starter and related circuit, tapping on starter will sometimes help to get it rotating. Check all fuses, and make sure battery terminals are clean and tight. Have someone or yourself connect a scanner DTC reader and see if you have any engine computer faults. If manual transmission make sure your clutch pedal switch is not missing the bushing. Aftermarket alarms can cause no starts also, but usually a "no-crank" situation.