1974 Carrera Cold Start Battery Drain

[Dick2.7]

Hello, I appeal to your 911 knowledge.

I have owned this beautiful targa for 5 years and it has never run properly. I have spent much money with a well known early 911 restorer, and it has improved, but it continues to backfire, and feels sluggish.

However, after replacing the battery twice, I was determined to locate the electrical fault. I attached a meter and located a draw of 35mA with ignition turned OFF. The draw returns to zero when I removed the middle fuse in the engine compartment labelled “cold start”. If I remove the fuse, it is a pig to start, but she now performs amazing at all temperatures. So, now I remove the fuse when I garage and no more battery drain. I insert the fuse to start, then immediately remove, perfect.

So my question. Whilst I have a work around, it would be lovely to fix the problem. Any ideas?

I am not a vehicle mechanic so it is unlikely I will repair myself unless it is straight forward. I am not completely incapable, having prepared a classic Panda 4x4 for PandaRaid last year. But this engine looks scary and it is too valuable for a mistake. I will most likely use your wisdom to instruct a 911 mechanic.