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Hi there, I have had trouble with Starting, The car does turn over but shuts down as if there is no power, although the battery is good, But I noticed that the inside of the alternator did not spin. Does not spinning prevent the car from Starting?. I thought it may be the fuel pump, or the spark plugs but I changed those along with water pump, radiator, belts, drove fine and normal, but I neglected to check the alternator during all of this and now all of a sudden doesn't want to rev up. Thanks..
 

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I mean right at start up, should there be any kind of spinning during the. Ignition sequence, I guess this answers my question, I know it should spin during the car being on, but since it doesn't spin when i attempt to start the car...
 

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Alternator should be spinning when the engine spin because it is connected by the pulley and belt -unlike A/C compressor it has a magnetic clutch. During ignition, the battery is powering the car. The alternator starts to give power when the engine already started. I dont think the alternator is the problem if you unable to start the car.
 

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AFAIK, my E46 alternator always spins inside when the engine turns (unless I have removed the belt). Doesnt' matter if the engine is running on its own or pushed by the starter. However, I don't think I have a clutch pulley on my alternator. I heard some alternators have a clutch and the voltage regular can engage the pulley or not, which means the pulley always spins but the armatures inside may not always spin. Maybe you have a clutch on your alternator.

But to get to the heart of your question, the alternator guts don't need to spin to start the car. During starting, the battery provides power to both the starter motor (to crank the engine) and to the spark plugs. I agree with ac_2007 that you probably have a fuel delivery issue. When was your fuel filter last changed? If you turn your key to "On" without trying to start, do you hear the fuel filter priming?

Otherwise some other possibilities are your CPS (crankshaft position sensor) went bad or one of your engine grounds is loose. Or if you recently replaced something, you might have failed to reconnect some important plug. I believe if the CPS has failed (or you disconnected it), the DME will refuse to send any spark to to the cylinders and the car won't start. If your car thinks you're trying to steal it, it might cut off the fuel pump power too.
 

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I've never heard of a clutch on an alternator... I know the newer BMWs can vary when the alternator charges the battery, but it doesn't user a clutch for that. When an alternator's coils aren't energized it's essentially freewheeling anyway so a clutch would be pointless.

Sent from my HTC Sensation 4G using Bimmer
 

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Thanks for correcting me. I guess if there were a clutch at the pulley, it would need an electrical wire to turn it on and off, or a heat-activated coupling like the cooling fan clutch on automatics. I could have sworn I saw ECS Tuning selling an alternator pulley removal kit that said it was for clutch pulleys. So what about the OP, what could cause his alternator to stop spinning on engine startup, other than forgetting to put the belt back on properly? Or maybe he's looking at the stationary part of the alternator's guts instead of the spinning part?
 
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