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Steve, BMW Expert
Category: BMW
Satisfied Customers: 25238
Experience:  BMW Expert
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My bmw 520i is failing to start.l bought a new battery,the

Customer Question

My bmw 520i is failing to start.l bought a new battery,the starter only laughing and the engine doesn't respond.whats the problem?
Submitted: 4 years ago.
Category: BMW
Expert:  Steve replied 4 years ago.
What exactly does the car do when you try to start?
Customer: replied 4 years ago.
If try starting,the engine/starter produces a Khhhh sound and the engine does not kick start.the engine will be wanting to kick but it's as if they is something can hear the engine wanting to start but this goes on until the battery get flat
Expert:  Steve replied 4 years ago.

The vehicle is not starting because it is either not getting spark, or not getting fuel. Most likely it is not getting fuel

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/broken line 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 familiar with the above then the testing should be carried out professionally.

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