[BioChemBro]

hi everyone

i have been dealing with a no start issue for a couple months (worse now since its warmer out). I can start the car when the engine is cold without any issues, but when the engine has warmed up, it will not start until the engine cools down..

This can take hours, however 9 times out of 10 i can hook up jumper cables from a separate car to the engine bay terminals and it will start INSTANTLY. as in no battery charging required

Things to note:
-The battery voltage via the engine bay terminals read ~12.25 volts when it will not start
-no long cranking whatsoever, fires right up when the jumper cables are attached
-clicking noise can be heard when its not starting
-Tapping on the starter does not do anything
-100% starts up when the engine is cold
-Upon close inspection, ground cable between engine and chassis looks to be in good condition
-All lights radio drive etc work when not starting

Could this be due to starter heat soak? even though the car will start when hot if jumper cables are attached?

thanks for reading, i could not find too many similar situations across multiple bmw boards

[BioChemBro]

initially i thought it was ground related, so i added an additional 4 gauge ground cable from the engine to the chassis. this worked the first week but no longer seems to provide any support

[opjose]

How old is the battery?

[BioChemBro]

Originally Posted by opjose

How old is the battery?

about a year old

[mxchris727]

i would start with a replacement battery. A faulty one can have sufficient voltage, but not the amperage (especially after being over-charged). Did you register the current battery?

[tlow98]

Battery voltage looks good, but have you had it load tested?

Sounds like a starter issue, but the jumper cables making it work instantly contradicts a starter issue. Hmmmm

[ptpending]

try to disconnect IBS sensor (it is integrated with negative battery terminal) when car is not starting
if that will not help you can try to check outside battery terminals which go outside near rear left arch, under arch cover

[BioChemBro]

Originally Posted by mxchris727

i would start with a replacement battery. A faulty one can have sufficient voltage, but not the amperage (especially after being over-charged). Did you register the current battery?

Yes i registered the battery when i bought it

Originally Posted by tlow98

Battery voltage looks good, but have you had it load tested?

Sounds like a starter issue, but the jumper cables making it work instantly contradicts a starter issue. Hmmmm

Getting it load tested this afternoon, or tomorrow. the jumper cables have me thinking its the engine to chassis ground strap, the car lived its life in houston before i had it shipped up to PA.. ground strap corrosion could still be an issue

Originally Posted by ptpending

try to disconnect IBS sensor (it is integrated with negative battery terminal) when car is not starting
if that will not help you can try to check outside battery terminals which go outside near rear left arch, under arch cover

I tried disconnecting the IBS cable, it did not make a difference. Ill check out the rear left arch battery terminals. thanks for the suggestion

[PhaseP]

Originally Posted by BioChemBro

the jumper cables have me thinking its the engine to chassis ground strap, the car lived its life in houston before i had it shipped up to PA.. ground strap corrosion could still be an issue

Aren't you putting the negative jumper cable on the side chassis negative post? Then it still goes through chassis ground strap to reach engine and started which is bolted to engine.

Like others I think you have weak battery or somewhere along the battery to engine cables/connections there is something loose and it is gets more loosened with heat. You can check your battery connections, battery to the trunk posts, then the battery plus to your junction box under the glove box. Look for anything loose, any sign of cable insulation going brown from heat at around any connections of those. It could be a relay too. Most relays are inside the ECU box, some are on the junction box under the glove box.

[SirHoward]

When that happened to me, it was my starter, had to replace it.

[cohenerickson]

Having an identical issue on my 07, did you end up finding out what’s wrong?