04 745i - Fails to start sometimes

Hi, for sometime now, when I press the start button, the starter doesnt engage with, and mostly without, a clicking sounds from the starter. I hear hiss sound of vacuum solenoids or something else, but no sound coming from starter motor.

After few minutes of pressing start button, the starter engages suddenly and the car starts normally. Most of times, the starter engage on the first press of start button, and the car starts without any signs of previous failures.

I had replaced the starter, then had a new battery installed, but it doesn't make a difference.

NO...it's not that I did not press the brake pedal hard enough, or not pressing the start button correctly, ....I am not that stupid....

I have tried turning off headlights and A/C to reduce power load and tapping near the start with metal object to discharge static electricity, but this doesn't help.

My questions.....

1. Assuming it is not a battery charging issue, how to tell if there is shortage causing a power drainage. I have no fault message of any kind on display while the car is not responding to start button.

2. Is it a DME issue? or faulty start-lockout relay module issue?

3. If I plug in a emergency battery pack into cigarette lighter, when the car doesn't start, to see if extra boost of juice can help, will I cause any electrical problem on the car? I am scared to try it...

I have read every forum post with similar problem but nobody has any clear answer to this "silent" problem that can't be demonstrated in the shops.....because most of times, car starts normally without any signs of malfunction.

Any of you BMW experts out there have a experience in correcting my problem?

Thanks very much.....

close to what mu friend had.
It stopped working one day thats it.
So he ended up disconnecting all modules and cleaning the contacts. especially one on the steering wheel.

My car is doing the same as the original poster. Intermittent issue. I've gotten it started in the past by opening door, closing door, locking then unlocking and start the starting process. TOday, however, this didn't work. What did work was using the switch in trunk to disconnect battery for a few seconds, then reconnecting. It started right up. I'm curious what models were cleaned from the friends car.

Have you checked the brake switch?
Do all lights come on but nothing happens?
Do the lights dim when it should be attempting to start but is not?

Great Questions. I have not checked the brake switch...that is a good lead. Not sure how to check it. Any ideas?

The lights do all come on and the wheel comes down and out like the car started. The lights do not dim, flicker or in any other way lead me to think that it is a voltage issue. What I do hear though is what sounds like a click/thunk noise that a switch would make or a starter that wasn't working correctly.

Lets keep it coming as I'm trying to avoid having the dealer put in modules, starters and other things that don't fix the problem.

Thanks

http://www.realoem.com/bmw/showparts...62&hg=12&fg=35
thats what you need..

Funny. I hijacked. I only think about my own problems. But enough about me...whats wrong with my car?

http://www.bimmerfest.com/forums/sho...d.php?t=482390

this is the answer to your problem..

OK. Looked at the int. supply module tonight. Looked for moisture and couldn't find any. Do you know if I can remove it, unplug the harnesses going to it and check for moisture or anything out of the ordinary and then plug it all back in with any weird consequences like reprogramming, etc?

Also ikob...I like you confidence. But you are so sure about it...not only to me but others. This would be a cheap fix...but why so sure?

Thanks

I had same issue 2 yaers ago and it cost me 2000$ doing and fixing differend things, which never fixed the problem the car had. afeter changing Integrated supply module car start acting way she was supposted to act.
lissen im giving you advise, its up to you what you will do.

Thanks. I appreciate your advice and even your advice about your advice. It sounds pretty easy. I'm going to try to take a look at it.

Thanks

Originally Posted by revrun

Great Questions. I have not checked the brake switch...that is a good lead. Not sure how to check it. Any ideas?

Without testing wires, you could just tap the brake pedal a few times and see if it turns over with no other changes.