Engine sometimes wont starts

[Yoni_d]

Hi All

Been out of the country for a long time...finally I can play with the Porsche again

I have a strange problem...Sometimes when I am trying to start the engine it wont starts. The engine is cranking but no signs of life.
The voltage on the battery is not so high - 12.6 volts (when cranking)
The same voltage is under the hood in the main "+" terminal.

When I connect the battery from other car to the "+" terminal under the hood the engine starts right away

I am wondering...if the engine is cranking in a good speed even with 12.6 volts, maybe the spark is not strong enough for the ignition? Maybe I have a loose wire or fuse somewhere on the way?
Any ideas what can I check/do in order to solve this problem?

Thanks guys!

Yoni.

[JhwShark]

I'm sure others will add to this...Since you get cranking from an external source...One might assume the connection between the jump post and control panel is OK (the heavy gage red wire from the post to the board). Also the similar wire from alternator to jump post...
Check the ground connection for the Bat as well as the cable itself for corrosion. While in the boot check the other ground contacts in the plastic connector. Use your volt meter as well to confirm voltage at the post and the panel.
What is the resting voltage at the jump post, at the bat pos, at the control panel.

After you started the car from the external source and removed the jumper cable what are the voltage readings at the jump post, at the bat pos, at the control panel (where the red wire connects)?? Is the red wire at all hardened??

Besides the Bat voltage possibilities...random FP relay or start relay (if AT) contacts/corrosion can cause issues.
COuld be a bad cell in the Bat

...just some info to start with.
Jon