wmmihail

Have a 2000 Z24 convertible I use seasonally. Late last summer the car started to exhibit slow cranking. It always started, some times after one try, most times after two, sometimes even took three but always started. Sometimes dash exhibited "Service Engine" and "Theft System" lights after starting but car always drove fine. Tested battery and OK. Further ruled out battery by trying several different. Bench tested starter at Autozone, they said OK. Further ruled out starter by trying another used starter, same slow cranking. One warm day last winter I tinkered with grounds between battery and starter circuit. That day car cranked normally. Thinking it was fixed I parked car. Next time I tried slow cranking was back. And now that car is seeing regular use this spring the slow crank still plagues me. Played with grounds again, no better. Tried jumping starter circuit from several locations including bypassing relay on radiator support and using a remote switch right at starter leads. Basically same slow crank, maybe a little better when I jumped leads right at starter. Last week I had a new development. Typical slow crank, car starts, maybe the 2 aforementioned lights lit on dash and than WHAM! The dash lights up like a christmas tree. All lights lit, coming on, coming off. Error code on odometer flashing then returning to normal than back to error. Analog guages drop to zero, back to normal, back to zero. I think you get the picture. Dash acted like it was possessed. Car drove OK but I sensed it wasn't perfectly normal. Got home with one stall but restarted fine. It was late, couldn't check anything. Next day car was perfectly normal, in fact the cranking was normal too. The normal cranking lasted 2 days than back to slow crank. Yesterday, again car lit up the dash and I definitely noticed a miss on acceleration. This time I pulled over and restarted car several times until the dash lights cleared. Drove home with no issues and car ran perfectly. I know this was long winded but I gotta believe they are related. Any suggestions would be greatly appreciated.

Segfault

You do have bad ground somewhere. Mystery lights are good indication of weird ground loops. Double-check the battery ground and engine ground, connect a voltmeter between battery minus terminal and engine block, turn starter, keep an eye on voltmeter, what's the reading? I'd say 0.5 V is already too much.

wmmihail

Yep. Bad negative battery cable. Drop test showed almost 5.0 V. Set up a redundant ground from negative post on battery to stud on engine to double check and it cranked nicely. New cable $6.49. Haven't driven much yet to make sure the dash lights are acting normal but I'm pretty optomistic. Thanks very much for the advice. Hope someone else benefits from this post.

Segfault

You are welcome!

wmmihail

Finally got to drive car this morning. As stated, cranking was fine but dash light issue is still plagueing the car. In fact, I had the extra added treat of having the radio turn on and off by itself. While sitting in the garage at work I was abe to notice that the turn/hazard inicator lights on the dash were also dimly lit with the engine idling. As I stepped on the gas they would brighten a bit but never fully illuminate. Does this all still sound like a ground issue? When I replaced the battery negative cable this weekend it was not an exact replica. The original cable had a ground strap crimped on about the midawy point where the insulation was stripped back. This connection was made to a bolt on the battery tray. I did not dulicate that connection detail. Did I loose any significant body ground because of this? On my way home I plan on fastening a temp ground with a pigtail to see if that helps. Thanks so much for the advice and thanks to you or anyone else who might have a constructive suggestion.

Segfault

Well, I'm not a modern car specialist. I used to know stuff, but it was years ago. Basically, intermittent battery connection is a bad thing to have while engine is running. Voltage regulator will not work properly and the voltage of alternator may reach dangerous levels. (I've seen over 50 V on a 24 V system.) Dangerous for on-board electronics. In short, whatever electronic unit is controlling your dash and radio may be "fried". Sorry for bad news.
I do not think your replacement cable has anything to do with this.
Good luck.

wmmihail

Well my test worked during my short drive from work last night. Car acted flawlessly. Made final connection from available pigtail on new negative battery cable and, using 10 gauge wire, connected other end to bolt on battery tray. Drove the car for a good hour after that and no issues. Thanks again. Hope someone benefits from this post.