Battery issue - battery's good, won't start unless jumper pack connected

[FantasiaWHT]

'97 328i (convertible).

Brand new battery (actually replaced a brand new battery because we thought it was bad but that obviously wasn't the issue). Tested it and it's in peak condition.

But the car won't start. Trunk lights, dash lights all come on when they should, but turning the key just gives me a whir and a click or two. If I hook it up to a jumper pack, it starts beautifully. Let it run for however long I want, doesn't matter. Turn it off and try to turn it back on again and nothing (or just a whir & click). Also the jumper pack is able to do this over and over and over again without needing to be recharged.

Ideas for where to start to track this problem down?

[Moron95M3]

Loose/poor battery terminal connections. Clean them, re-tighten your cables.

[Eric93se]

If that doesn't do the trick, there may be a loose connection on one of the terminals at the jump box. If none of that works then the jump box may be cracked.

[FantasiaWHT]

Thanks! I'll get looking at those two things.

[Turbohugh]

check your ground points.
also inspect cables

[XnWarden]

Check the ground strap that runs to the motor mount arm. Connect a jumper cable from the lift point on the vanos to a strut tower bolt. If it starts then your engine ground is bad

Sent from my VS987 using Tapatalk

[Turbohugh]

Shhh!!! The point is for him to check them all!

[shogun]

check the fusible link https://www.bimmerforums.com/forum/s...328is-No-Start

[jc43089]

Not the fusible link if it runs and starts sometimes. It sounds like a loose connection/ bad ground on a large power cable.

[shogun]

yes, it can also be the fusible link if it runs and starts sometimes, then the fusible link has a haircrack and sometimes works and sometimes not. This is not internet experience, my own experience , car was starting sometimes, sometimes dead http://www.bimmerboard.com/members/s...ible_E32_1.jpg
But of course it can also be a loose connection/bad ground.

[gc325is]

Are you using the battery post in the trunk to jump start the car or the under the hood remote terminal posts?

[FantasiaWHT]

Are you using the battery post in the trunk to jump start the car or the under the hood remote terminal posts?

Posts in the trunk.

[Eric93se]

It may be your starter that is bad and it's just a coincidence that it's starting when jumped.

What is the battery voltage with the car off and when it's running?

Does the car ever start without it being jumped? (if it does then it's most likely your starter).

[gc325is]

So the statement is my car does not start with a battery alone, I must add the jump box to it to get it to start.

As said put a Volt meter on the starter and read it. Sounds like you may have a high resistance drop for a battery alone, loose connector to starter, corrosion on wires bad starter.