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Thread: It all started with a dead battery

  1. #11
    Senior Member Scott A's Avatar
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    A little unrelated, but kinda something to look out for.

    On a 914. The ground strap at the tranny/body was bad. So the car looked for a new ground and used the parking brake cable. It severely melted the plastic jacket and welded the cable to part of the body. It totally fried up the cable. I could smell something…and maybe I remember hearing something. But it was the smell that got me looking…. Because it was such an unusual problem.

    On the 911, it was similar, I don’t think it was the ground strap at the tranny. But a ground near the alternator. But that lack of ground caused the 16 pin connector to fail, heating and melting between two pins.
    Which I noticed after I snapped open the 16 pin connector.

    Current long term ownership: 63 Cab, 71 911, 74 914

  2. #12
    Thanks Scott, I checked the major grounds first, tranny, distributor to case, CDI panel grounds, fuel console grounds, alternator ground, coil ground etc. and everything checks. Checked resistance at coil and and the 2 wires going to distributor again and console plugs and wires again. Pulled front skid pan to see if kinked or cracked fuel line going to the fuel tank as well as tracing fuel lines from chassis to fuel pump then to fuel console and MFI pump. Tomorrow I'll continue with the puzzle. Appreciate the input!!!!

    Kevin

  3. #13
    Senior Member
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    This might be a crazy comment - but it is not clear how long your car was stored, so are you sure the fuel is not bad?
    Bill

    Early 911S Registry Member #4087
    Instagram: @myflat6

    '72T hotrod 210 0228
    '82SC Targa
    '97C4S (sold - and regretting it)

  4. #14
    Bill, I drive the car at least 3 times a month on weekend spurts! Probably 10-20 miles per drive.

  5. #15
    Senior Member
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    Quote Originally Posted by kwikt View Post
    Bill, I drive the car at least 3 times a month on weekend spurts! Probably 10-20 miles per drive.
    answers that!
    Bill

    Early 911S Registry Member #4087
    Instagram: @myflat6

    '72T hotrod 210 0228
    '82SC Targa
    '97C4S (sold - and regretting it)

  6. #16
    Senior Member
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    Quote Originally Posted by kwikt View Post
    The car ran great up until battery died about a month ago now. Like I said I jumped it with my F150 and started right up and ran great while i drove it around the block to park it back in the garage. Turned the key and NOTHING. That's when I purchased the new battery and problem started.....Today i checked voltage at center plug going to CDI 12.3 volts so I have voltage! I'm checking grounds to see if bad connections. I was just going to swap batteries from my truck just for the hell of it who knows.

    Is this 12.3v without the car running. Or with the car running. Doesn’t sound great to me. CDI boxes are voltage sensitive.
    looking for 1972 911t motor XR584, S/N 6121622

  7. #17
    Senior Member
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    Quote Originally Posted by edmayo View Post
    While you're at it check for battery drain by removing ground strap and using an ammeter to check for battery drain. Should not be more than 25 milliamps. Still want to know why battery died with even with battery tender on it. Exactly how long ago was it that car ran perfectly. Week, month?
    (

    I like Ed's path. A short to ground would drain the battery and maybe get worse with vibration when starting the engine. I would by-pass the CDI(I say CDI as you report gas fumes meaning the fuel is not getting ignited and you report 12.3 volts which is about a half charged battery-12.6 is fully charged) and jumper 12V directly to the coil and see if it runs. I by-passed my MSD CDI this way and found an input power issue with the voltage being lowered going through a fuse. I have a 69 with Marelli and carbs, so suspect bypassing the CDI on a 72 is a lot more complicated.

  8. #18
    Yes that's 12.3 with the car not running but according to the manual 11 measured volts is required with ignition on not running. Not sure if it makes a difference.

  9. #19
    Have you checked the output voltage of the alternator?
    Dave Reu
    Member #3949
    1973 Silver Metallic 911S

  10. #20
    Yes Dave, I checked it at the battery while running 13.8 volts.

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