Car won't start even while being JUMPED???


Asked by Feb 04, 2014 at 08:53 PM about the 1997 BMW Z3 2 Dr 1.9 Convertible

Question type: Maintenance & Repair

I have a '97 Z3 and I'm completely perplexed.  I have replaced the alternator and
battery, checked the battery terminals and they're fine.  What is happening is with this
last cold snap, I had to jump the car in order to get it started (it was in our detached
garage which is not heated but at least the Z is protected from the elements).  I got it
started, put in gear and started to reverse.  The car died. Jumped the car again, left it
attached for 20 minutes, the same thing happened.  

I have no idea what could be going on.  I replaced the alternator less than a year ago
and replaced the battery just this past December.  The ground to the battery is tight.  

Went out to mess with the car again, see if I could get it started and this time it wouldn't
even start while jumped.  

Any ideas?

6 Answers

break out with the wire brush....clean the lug end that attaches to the frame ground....the spot where the lug bolts to and that 1/0 battery cable lug too~ with renewed ground potential... systems will work properly again,,,,in addition to the MAIN ground connection to frame...there is also one 1/0 battery cable connecting to the motor block as well (near the alternator) the starter motor can pull the requisite 300 or more cold cranking short your battery ground cable is full of road salt and rust....clean it till shiny with a wirebrush...use a NEW bolt if you can...without any corrosion on it~

1 out of 1 people think this is helpful.

sounds like the battery is dead.. new or not have it checked just stay away from interstate battery's there no good here in the cold there sissy hot climate battery's for out west better off using diehard in this cold...

1 out of 1 people think this is helpful.

ya I know you cleaned the cable...the clamp end...the other end (the business end) is what we need cleaned to allow FULL amperage through...yet supply an unwavering 12 volt source for the heated 02 sensors the ECU the TCM the BCM and auxilliary components such as winshield wiper motors and power windows~

1 out of 1 people think this is helpful.

...good point tt, check the 'knock off' labels on the top of your battery...these tell the date of it's first charge...since the tin/antimony alloy batteries will degrade approximately ten percent per year (stop accepting a charge) it is important that this battery is NEW and fresh if you are gonna make it through this cold snap okay~

correct me if I'm wrong, but the BMW's have TWO main ground leadin' to the chassis and one leadin' to the motor~

1 out of 1 people think this is helpful.
Tom Demyan

Yes , there are 2 grounds, but like ttribex said, it's probably your battery. What is the voltage? If you can't jump start it, it probably has a shorted cell. Remove the battery and take to a local auto parts store, they will test for free.

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