Starting problems

Let me start off by saying I have searched on this for weeks and talked to numerous BMW mechanics. Also I have worked as a painter at a hot rod shop for going on close to 15 yrs so have knowledge but we don't deal with a lot of fuel Injection or computer stuff and my mechanics here are stumped as well. A few weeks ago the battery went dead on our 07 328i we had to jump it and did that under the hood. Ran for a few days then happened again so went and bought a new battery for it and did fine, so dunno if thos could b a prob with whats happening now a few days after this my wife gets in it and it turns over and over, tries to fire and goes dead over and over. Finally after messing with it, finally starts, once it started drove ab 50 miles did fine and kept starting the rest of that day. Next morn won't start again and this happens for days can finally get it started over messing with it will continue to start then next day will not, was told to swap keys so did thT and no change, checked fuses, checked fuel pump and power to the pump, checked relays, was told to fill the tank and if did fine then started acting up at a half tank then syphoner in left side of tank is bad, filled up but no change, sprayed carb cleaner in intake and still took ab ten tries of turning over to start, so at this point I'm stumped. Stumped on if it's fuel or fire as well And the Beamer place told me with me knowing a bit of what to do I should keep trying to find the problem cuz if I take it to them there gonna have to do the same thing were doing possibly not find a problem and have a big bill. Any help at all would b greatly appreciated. Thank you

Did you buy an OEM battery? Because these car are very temperamental without the right amount of voltage.

Yes i did.

Also I checked voltage, and it's getting what it's suppose to, turns over great just right when it fires goes dead over and over.

Its probably not your battery, does it run smooth once you get it started?

Once I finally get it started runs perfect and usually will start right up the rest of the day, once sits for ab 8 hrs just turns over tries to fire but won't, like it's not getting fuel but everything seems to be working properly.

Wow, I'm as baffled as you, I'm trying to search what it might be to try to help, you're gonna have to divide the issue in all three parts? Oxygen, Spark and Fuel, which are the three components needed for a car to start, sometimes it helps when you focus on only one at the time.

Fuel pressure regulator maybe?

Spark wise I figure might b something I won't find seeing that there's all these chips that could burn up and all that. I figured spraying carb cleaner in intake if were a fuel prob should have fired right up but still didn't And have pulled fuel pump out and tested and tested for fire everywhere. Also if would have burned up a chip in the key or something figured it wouldn't start at all but once starts runs fine til sits for a while which makes me feel like it's fuel but cant find anything anywhere that's not working properly fuel wise. Will say the only thing haven't checked or looked at is the fuel filter but I'm thinking if that were the case it would occasionally act up driving if it were trash in it and doesnt and also it's basically the same routine everyday with it which has me completely baffled.

So far you have checked everything I would if it was my car. What really throws everything off is that it runs great once started.

Yep, and I mean it runs perfect, our shop is ab 45 mi from house, actually drove it today, went out this morn, turned over and over for ab 15-20 min or so this time the last few tries u could hear it trying to run but still go dead after just a couple sec, the last try when it fired gave it some gas sputtered a bit and started running, I could walk outside right now and will fire right up but by tomorrow morn it won't start again.

Sucks to have such a beautiful machine and have that issue, wish I could have helped, good luck, try google you might find a thread.

Sounds like a fuel pressure problem to me. After it has been sitting, turn the ignition on without cranking it over. Let the fuel system pressurize for a minute or two and then try cranking it. If it fires right up then the fuel pressure is not building up for whatever reason.

Also, don't spray anything down the intake of a fuel injected car. The Mass Airflow sensor will get messed up if you coat it with anything you might spray down there.

Yes I'm aware I sprayed in the actual intake not at the mas which was what BMW told me to do. I actually tried that, left the key on And also cycled the key on and off a few times as well but never changed the outcome. Was the only other thing I could thing of was the pressure was leaking off over time which was causing it to not fire until after so long it finally builds ip pressure to start but of this was the case where could the problems be to cause no fuel pressure? Fuel rail or pump or what else? Also is this like any other engine like the LS engines with the fuel rail and the pressure valve at the end where I could actually hook up a pressure gauge? This wasthe only other thing I could think to do.

Even if that were the case still should have fired for few seconds when sprayed the intake I would think.

Get a code read or code reader.
See if there are any error codes.

Did that as well, no codes.