intermittent no start - can be fixed by rolling the car forward

[mike okisbig]

Hi all

Car is a 1999 528iT automatic

Symptoms: occassionally, and without warning, the car will unlock normally with the remote, interior lights come on, door chime sounds with key in, dash lights come one, etc. Go to turn key to start position and....nothing. Everything goes completely dead. No lights, nothing. Turn key off and try again, still dead. The last couple of times this has happened I've been in a position where I can roll the car down an incline (my driveway) in neutral for about 100 feet and if the key is still in the 'on' position the car will come back to life and start normally and then start normally after that until the cycle starts again.

Any ideas? Battery isn't draining as the car starts fine once it 'comes back to life'. I was thinking ignition switch but it doesn't have any of the other strange failing ignition switch symptoms with the sun visor lights, etc

Thanks

[Santaclaus4]

A loose battery connection can cause the same problem. Moving the car causes it to "jiggle" and make a connection.

[mike okisbig]

Yes, I thought of that too. The battery cables are on very night with no play in any direction.
Thanks for the reply

[DennisG01]

Did you also check cables (positive and negative) at the engine bay/starter? How clean are the connections?

[Santaclaus4]

The symptoms totally reeks of a loose battery connection somewhere. Perhaps a switched connection. The car may still have electrical power but an electrical contact may open (due to a loose wire perhaps) and remove power from several switched systems in the car.

[mike okisbig]

I'll check the connections and report back. Thanks!

[BimmerBreaker]

Hows your starter?

[mike okisbig]

Starter seems fine, always fires on the first crank (when it has power ;-) and doesn't exhibit any other problems.

[BimmrMeUpSnotty]

My ground cable from the battery came loose at the connection to the rear quarter panel a couple times in my 540 in the past. Should be a 13mm nut.

[geargrinder]

The symptoms totally reeks of a loose battery connection somewhere. Perhaps a switched connection. The car may still have electrical power but an electrical contact may open (due to a loose wire perhaps) and remove power from several switched systems in the car.

I completely agree with Santa.

[mike okisbig]

I think it was a loose positive battery cable on the battery. I took both cables off, cleaned the terminals, and reinstalled them and it seems to be fine now. Fingers crossed!
Thanks all.

[WBAD530i]

I had a similar problem with my 530. The battery connections were tight, but it still lost connection after driving/parking intermittently. The fix was to go out back to the battery and wiggle the BST (Battery Safety Terminal). I knew it was good if my trunk light came back on. This is the piece that has a small explosive charge to disconnect the battery after impact from a wreck. Normally when this blows it has to be replaced to get the car going again, but I believe they can over time from removing the positive terminal too many times create a "soft fail" scenario.

[WBAD530i]

Also to add to the above ^ If your car does not have the battery hold down bracket in place it can cause the battery to shift a little and likely put tension on your cables. this was the cause to my BST failing all the time. I didnt have the bracket.