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Steve, BMW Expert
Category: BMW
Satisfied Customers: 23983
Experience:  BMW Expert
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2003/ bmw 330i - car will turn over, but will not start. It

Customer Question

2003/ bmw 330i - car will turn over, but will not start. It did the first time i started it, but then turned it off to see if it would restart and did not. And, has not started for two days...
My MAF sensor has been acting up, sent code..and read with scanner p0102. At first it would cause vehicle to acting like it was bogging out at high or low speeds. Changed the oil, and clean the MAF sensor and that same night would not start. I will being replacing MAF sensor today, as it arrives at noon. I did also check the fuel pump fuse all was okay.
What could it be, would the MAF sensor cause vehicle not to start if its gone bad? how to diagnose?
Submitted: 1 year ago.
Category: BMW
Expert:  Steve replied 1 year ago.
what is fuel pressure?
Customer: replied 1 year ago.
Greetings do I check that ?
Expert:  Steve replied 1 year ago.
with a fuel pressure test guage...
Customer: replied 1 year ago.
Just saw video ...YouTube to check for pressure...
Expert:  Steve replied 1 year ago.
what question would you like answered exactly? would you like to know possible causes for the no start?
Customer: replied 1 year ago.
I would like to know if MAF sensor would cause car not to start if bad...and other possibilities. ..that I have not checked..As it cranks over..but won't start...
Expert:  Steve replied 1 year ago.
I will provide an honest answer. I trust this will be appreciated. Please remember that a low rating PUNISHES me for being honest and that I receive nothing for my time until a positive rating is clicked.
The vehicle is not starting because it is either not getting spark, or not getting fuel – or getting fuel/air in a very wrong mixture. It is uncommon for a MAF to cause a car not to start. However, simply unhooking the MAF and trying to start with it unhooked can confirm.
No spark would most commonly be caused by a bad crank sensor, bad main relay or bad engine control unit. Sometimes it can also be key or anti-theft related.
No fuel would be caused by a blown fuel pump fuse, clog/blockage/bro***** *****ne of some kind, bad fuel pump relay (if fitted), or bad fuel pump. Relay failures are quite rare, however.
Depending on your abilities and equipment/tools, you may or may not be able to diagnose further.
The simplest thing to do (after checking the fuel pump fuse) would be to spray quick start / starter fluid into the intake (carefully) while cranking. If the engine starts on this, then you have spark and the problem lies with fuel delivery and can be further traced from there.
Another check would be for power at the fuel pump, and to see if it is running or not. If power is present and it is not running, it is confirmed as having failed. If the pump is running, pressure may not be correct, so it also needs to be tested.
If I had to give a guess, I would say it is likely a bad fuel pump.
If you are not comfortable or familiar with the above then the testing should be carried out professionally.
Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.