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Old 06-07-2018, 05:43 PM   #1
cherwool
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E46 M3 random starting issue - anyone else experienced?



Hi guys,

New here but longtime BMW owner. I'm having an issue with my E46 M3 on and off where every couple weeks it has trouble starting on the first try.

Not related to weather, temperature, drive length, or anything. It is completely random.

The engine cranks over strong, but unless I cycle the key on/off a few times it won't catch and start.

I've replaced fuel filter this year, it had new coil packs two years ago, battery and starter are strong, and fuel pump seems fine because I've never had any other issues with it.

Anyone experience this or know what might be causing it?

Thanks
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Old 06-07-2018, 09:55 PM   #2
jabela
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Flaky crank position sensor maybe? You might have better luck on m3forums or e46fanatics.
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Old 06-08-2018, 10:17 AM   #3
sloveniaboy
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try waiting for a few seconds before you start the car and see if that resolves or at least reduces the amount of times the car doesn't start on the first shot.

key in and turn to start position, wait for the fuel pump to finish priming (few seconds), then try and start

let us know
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Old 06-08-2018, 11:21 PM   #4
cherwool
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Thanks guys - tried priming the pump first, but it doesn't seem to affect the issue. That's why I'm led to believe it is probably not a faulty pump? Correct me if I'm wrong
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Old 06-08-2018, 11:23 PM   #5
cherwool
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Quote:
Originally Posted by jabela View Post
Flaky crank position sensor maybe? You might have better luck on m3forums or e46fanatics.
Could you explain the sensor purpose? This might make sense at it seems to only affect start up and not actual fuel delivery.
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Old 06-08-2018, 11:35 PM   #6
jabela
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Quote:
Originally Posted by cherwool View Post
Could you explain the sensor purpose? This might make sense at it seems to only affect start up and not actual fuel delivery.
The CPS tell the ECU the position of the crankshaft and when to fire the injectors, spark plugs, etc. If the ECU doesn't get the signal from the sensor, it wouldn't start properly. It could be that the sensor is soft failing, and works once it's warmed up or something like that.

Likely not a pump issue if you hear it running when you turn the key. You'd also have more driveability problems when you were flooring it when driving.

To start the engine you need fuel, air and spark. You also need the starter to crank the engine to pull in the air.

It sounds like you have everything but fuel or spark. You might also be missing air if your ICV or throttle is somehow stuck shut.

If you could connect a decent OBDII scanner, or better yet, the BMW INPA software, you could see your vacuum level, fuel, spark timing, etc.

Maybe BMW owners have the software on their laptop, you could get it or ask someone nearby.
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Old 06-10-2018, 06:13 PM   #7
cherwool
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Quote:
Originally Posted by jabela View Post
The CPS tell the ECU the position of the crankshaft and when to fire the injectors, spark plugs, etc. If the ECU doesn't get the signal from the sensor, it wouldn't start properly. It could be that the sensor is soft failing, and works once it's warmed up or something like that.

Likely not a pump issue if you hear it running when you turn the key. You'd also have more driveability problems when you were flooring it when driving.

To start the engine you need fuel, air and spark. You also need the starter to crank the engine to pull in the air.

It sounds like you have everything but fuel or spark. You might also be missing air if your ICV or throttle is somehow stuck shut.

If you could connect a decent OBDII scanner, or better yet, the BMW INPA software, you could see your vacuum level, fuel, spark timing, etc.

Maybe BMW owners have the software on their laptop, you could get it or ask someone nearby.
Thank you - this is very helpful.
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