vettdvr

The hall effect sensor is basically a coil of very small wire that when a magnet mounted in a rotating device such as flywheel cam etc passes close to the sensor a small pulsating signal it produced. This signal is then applied to the Main computer to indicate the engine is rotating and to then fire fuel/plugs etc. The most common failure mode is age/heat causeing the tiny wires/coil inside the sensor to open and therefore not produce the pulse signal needed by the computer for the engine to run and a no start condition exist. It is possible for some random pulse to be sent allowing the engine to run until warm up and once again coil opens. Easy solution replace sensor.

cm60k

^^WELL SAID^^..

ZAYED,,

wonkaa

ive changed the fuel pump relay and the CPS.

still not starting up. its trying to. if anything its become a bit more calm. before when trying to start the car would shake a lot but now its just turning over but then just turns off after a few seconds.

any other options?

after replacing the CPS i disconnected the battery for about 30 seconds just incase, not sure if that does anything but yea..

anything else i can troubleshoot? already spent NZ$200 so if nothing else ill get it towed to a mechanic.

should i get a friend to scan for error codes? and also the previous problem with the MAF is still there but i really dont think that the MAF is the cause for the car not starting up..

thanks..

vettdvr

What we don't know is, fuel pressure? Can you put a gauge on the rail and verify pressure while cranking.

ibeforreal

It might sound a bit crazy but you could have a blown fuse. Check your fuel pump fuse.

Once you disconnected the battery for about 30 minutes most of the stored codes have been cleared. However, if there is a problem they will come back.

Did you try cleaning the MAF? That is about a $7 can of MAF cleaner.

cm60k

That's weird..!,

if replace CPS & relay not helps, means need to diagnose the car, no need to spend more $$$ & time for nothing,,

don't forget to check the fuel delivery, in the same time when you diagnose the car...

ZAYED,,

ibeforreal

Checking the fuel pump fuse is free and the fuses if blown cost less than $1.

cm60k

He already checked the fuse in post #14 John, no problem with double check..

ZAYED,,

wonkaa

Could it actually be thr starter motor?

I just remembered that the car used to display msg that says something like, "battery protection, convenience functions are unavailable."

This has come on randomly during the past few days including currently.

As well as in the past, it was quite random.

cm60k

How's the condition of your battery..?, do you know what's the battery out-put..??

if you have a problem with MSG before, your alternator or alternator regulator goes bad..!?!

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wonkaa

Not sure. It was a public holiday yesterday so long weekend. No one working. I have a friend who can run diagnostics coming on monday..

I think the battery is ok but maybe the aux battery? How to check?

Checked the main battery voltage by the on board computer.

shows UB: 11.5V

cm60k

You can test the battery with Multimeter/Voltmeter or Load Tester,

If the battery voltage is 12.6v/12.8v or higher means battery is good,, if it reads anything below 11.9v would be considered it's mostly dead...

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wonkaa

Normally the battery is 11.5v

I connected with another BMW via jump cable and reading showed 12.9-13v but still wont start..

cm60k

I think your battery soo weak..!, starting DIN will be down either,,

it should be more than 12.6v, prefer if you can get another good battery, it will helps to see if starting issue caused from weak battery..!!

ZAYED,,

wonkaa

Yes but if i connect to friends car battery why jump start not working?

Also, i think the small battery is also bad. what is the correct voltage for the aux battery?

cm60k

There is something else for starting called DIN/EN, it may goes bad during of lower voltage..!,,

Aux. battery is 12V, 12AH, it should not reads below 9.4v, did you test that..?

ZAYED,,

wonkaa

What is din/en?

I cant check the aux battery i dont have a voltage checker..

Also how about alternater? Can that cause the car to not start?

cm60k

It's the cranking power, depend of battery spec.,



alternator provides power to whole Electronics, and supplies power for the vehicle while the engine is running,

When you start the car, power is taken from the battery to alternator to recharge it,

if alternator fails, the car will begin using up the battery for supplying power, then battery will run low, after that car will die,,

and need jumping or new battery..!

ZAYED,,

wonkaa

i got a voltage checker and checked the batteries.

main battery in the boot : 11.6V

aux SBC battery in the front : 12.4V

still not too sure what the problem is...

cetialpha5

I don't think it's your battery. Mine reads 11.5 volts and it's about 19 degrees here. I believe the battery low messages kick in when it's 11 volts and a second message kicks in at 10.5 volts.

Do you have any CEL lights on? You can get a basic ELM327 scanner that costs around $25 in the US (the BAFX from Amazon), works with Android and the Torque app is about $5. It scans basic OBDII codes, but it won't do more complex systems though.

wonkaa

unfortunately i am not located in the states.

the CEL was on for like 6 months prior to the car not starting due to a faulty MAF which is yet to be replaced.

but i dont suspect that causing the car to not start.

thanks...

cetialpha5

You could also try getting an X431 EasyDiag from Launch. I got it from Aliexpress and the vendors there ship worldwide, only cost me $25 for it but I haven't really used it yet so I can't say if it's any good. Reviews are 50/50 some like it, some don't. They have versions for android and iOS. They charge another $39 to read Benz specific codes and cover other systems. Took them 2 weeks to mail it to me though.

I think your first step is to get the CEL read, with it on all the time, there could be additional codes that might tell you what's wrong. In the US, most auto parts stores will read the code for free and even let you borrow tools. I borrowed a store's code reader once just by leaving my license.