E39 M5 total power loss starting problems

Heinekelover100 · 14th September 2011, 17:06

I have scoured the internet and not come up with much hopefully someone can help. I got up this morning went out to the car and my trunk and doors opened just fine. When I went to start the car I got about a quarter turn on the ignition and lost all power in the car. I hooked up my booster thinking the battery might just be dead let that sit for about and hour and tried starting again now had power in the car but it would not turn over. When I disconnected the booster the power now remained on and checked the voltage at the battery it was reading 12.4V. So I tried to star the car again now with no booster and when I turn the ignition I loose all power again just like I did the first time. I now went back to the trunk to check the voltage again and as soon as I touched my voltmeter to the battery the power came back on. My suspicions are a bad battery though it is only 18 months old and I have had no problems, my starter is dead but that does not explain the total power loss, I have a ground shorting issue? Thanks in advance for the help. Kyle

Mike S. · 14th September 2011, 17:13

First, check your battery cables and make sure they are clean and tight on the battery posts.

Second, start shopping for a battery as it sounds like yours is probably spent. I think you need to see a bit over 13V when you check it. I think.

Heinekelover100 · 14th September 2011, 17:14

I have checked the connections and they are all good. I am about to pull the battery and take it to autozone to check it out.

bcampbe7 · 14th September 2011, 17:50

Check all wires coming off the battery. Are they corroded or brittle? Wiggle them.

I know it is not the same car, but years ago I had a Supra that just died while leaving work one evening. Lights, everything went out and car shut off. I had it towed home and the next morning was going to have it towed to a shop. The tow truck guy showed up and I told him what had happened. He said, "pop your hood." He wiggled a smaller gauge wire on the positive side of the battery and it just broke off. There was the issue! I cut it back (leaving enough room to reach the battery but still got rid of corrosion) put a new connector on it and reconnected. Car fired right up and never had another issue with it.

Heinekelover100 · 14th September 2011, 18:25

Thanks for the response. Looks like I got to the bottom of it I removed the battery to have it checked it was fine as I suspected. Despite the terminals and cables looked good I cleaned them up with some steel wool and replaced the battery with dielectric grease on the connections and I am now up and running again.

Sailor24 · 14th September 2011, 19:17

Although you are up and running it might be because you moved the wires around. There have been a few cases reported on the board of the ground from the battery being loose where it bolts to the car. Just follow the ground wire back to where it bolts to the body to find the location it is not far. Your symptoms are the same as theirs.

Heinekelover100 · 14th September 2011, 20:37

I will give that a check tonight. Thanks for the heads up.