Chasing a possible power issue

[jwatson]

Hello Everyone

So for month now I have been having issues with my 05 Z4. Sometimes I will go to turn the car on, I place the key in the ignition, turn the key and the car dies. I initially thought this was a battery issue because every time I I would check to see if my battery was good, the car would power back on if i touched or slightly adjusted either positive or negative terminals. I replaced my battery and the problem still continued. I have changed my starter motor, I have changed my ignition and just yesterday I changed my voltage regulator. None of these have solved the problem, so i am left to assume that I have a bad ground strap somewhere. Would anyone happen to know where the ground straps are located for this vehicle? I cannot seem to find any kind of guide or diagram that would tell me.

[wdb]

Have you searched realoem.com? It's not perfect for locating items physically but it might give you some hints.

It sounds as though you might have an issue near the battery somewhere. Another place to look would be the grounding strap for the engine block. That should be fairly easy to find.

[Clearancediver]

One ground strap is on the passenger side of the engine....

Attached to wheel fender...on my '04 it's a round cable.

I would also check the BST to see if it had functioned. The BST is part of the battery cable in the battery well. If it blew and remained slightly "engaged" it might replicate this issue. Slight possibility but suggest this as a result of you wiggling battery cables and engine starting up afterwards...

[jwatson]

Originally Posted by wdb

Have you searched realoem.com? It's not perfect for locating items physically but it might give you some hints.

It sounds as though you might have an issue near the battery somewhere. Another place to look would be the grounding strap for the engine block. That should be fairly easy to find.

I will check this site out. Thanks!

[jwatson]

Originally Posted by Clearancediver

One ground strap is on the passenger side of the engine....

Attached to wheel fender...on my '04 it's a round cable.

I would also check the BST to see if it had functioned. The BST is part of the battery cable in the battery well. If it blew and remained slightly "engaged" it might replicate this issue. Slight possibility but suggest this as a result of you wiggling battery cables and engine starting up afterwards...

I will take a look down there and see if I can find it. As far as the BST, I dont see any signs of it blowing, but I may not know what Im looking for. Minor clarification, my engine doesnt start back up after wiggling the wires, power just comes back to the car. I don't know if that makes a difference in your assessment or no.

[Clearancediver]

Really confusing statement that your car doesn't start up after wiggling cables but power just comes back to car.....

Care to explain....

Normally you need to engage ignition/starter to start car... is that what you mean? And if so... how long after wiggling wires does the power "comes back"

[pungo]

Throwing parts at a problem is not the best way to resolve it. Diagnosing/testing/troubleshooting is more effective and cheaper. I'm having trouble understanding your exact symptoms so I can't recommend how to diagnose the problem.

[JAS1169]

Your car initially wouldn't on occasion start. In your search to determine the source of this no start problem you wiggled the battery cable and power returned to the car, yet the car still lacked power to start the engine.

The BST, when its safety mode is initiated, is designed to allow power to the car for light, hazards, telephone etc. but, provide no power to start or run the engine. This BST safety mode is mirroring what you saw happen when you wiggled the power cables. In that, no power to start the motor, but power to other things in the car. The BST has to be in the center of your problem because it is the only device which is intentionally designed to allow some power to the car and at the same time prevent power from reaching the engine

Your BST is no longer functioning correctly and has developed unknown faults. If this was my car I would replace the entire positive cable (with it's build in new BST).

[jwatson]

Hey everyone. I know I was gone for a minute but I did want to give an update on this issue. I did FINALLY get the problem resolved. As a couple of you have guessed, this turned out to be a problem with the BST. I ordered an entire new positive wire and replaced it and now the car is having no more issues. Thanks everyone!