BMW z4 won’t start

A

AdamZ4

New member
Hi my bmw won’t start, the batter voltage is 14v the positive connector in the engine compartment is also showing 14 v I disconnected the ins and it. Still would not start. I have replaced relay 30 and still won’t start.


The only? Way I can start it is fronm a jump pack on the positive connector in the engine bay. Any ideas? Thanks
 
Might be a problem with the battery. If the car isn't running, the battery voltage should not be that high.
 
I know it's been said a thousand times on here - but battery battery battery!!!

Check the age of it - if it's >5 years old, it's very likely fooked & just needs replacing.

14v on a multimeter? Normally you should see about 12.5 - 12.7 volts fully charged (which also means little).

It's CCA that starts the car & you won;t measure that with a multimeter.

£100 every 5 years, consider it a maintenence item.
 
It does sound like you battery isn’t delivering the amperage to start the car, especially if it will start from a jump.
 
With one or more dead cells the battery will still show normal voltage but, as said, won't have the current capacity.
14v should only be showing on a meter if a charger is attached. If you really do have a constant 14v at rest in a 12v battery, I would stand well back.
12.8v is around the maximum which should be indicated for a fully charged battery.
 
Said a million times, you need obd reader to check fault.

On my car it was reported by the obd code reader the key module was faulty.
Ordered took 2 weeks to arrive at dealer.
I replaced it car still wouldn't start.

By then the drivers window was stuck open, the cover i put on blew off, rained in, shorted the foot brake stop switch (didn't know at time)..
That then blew something in ABS unit module (came back as pressure sensor fail).

I replaced battery, the starter, finally brake switch from Eurocarparts, which was new but faulty (tail brake lights stuck on) :x so lead me down another path.

Replaced ABS with second hand, fitted second brake switch (in fact cheapo from ebay) and car finally started having stood for 6 weeks.

All i can say is good luck.
 
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