924Board.org

[ourkid]

This has happened twice recently - I leave the car in work and forget to turn off the CD player (it has a wierd on/off switch so comes back on by itself),so when i try toi start it,the battery is a bit low,BUT is showing 12v on gauge,cranks engine only SLIGHTLY slower than before,all ancilliaries work, and will crank for a good 20 secs at a time before going flat.
The car will not make any attempt at all to fire,not a whisper.This is not a battery issue as it is fairly new and the last time it happened was with a different,also good battery.

SO, my car appears to need a fully charged,strong battery to even Attempt to fire up.I'm now showing 13.5 volts running and it fires up with it's usual 1/2 crank.

I've had cars in the past that will start,even with a battery almost flat,is this a characteristic of the ignition/injection setup or is something else going on?

Oh - all my earths are clean/new and i have an extra earth from battery to body.THe battery holds a good charge for weeks when the car is not used so i'm sure i have no shorts anywhere.

Thanks,
Ade.
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1983 924 N/A

[Ozzie]

um- put an isolating switch or rewire the power to the CD?
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[ourkid]

Thanks Ozzie,

I was really questioning why my car didn't fire with a battery that was quite capable of cranking the engine,working lights etc.It was only a bit low.
With a fully charged battery it fired straight up,so either these cars always need a 100 percent good battery,or mine has a fault somewhere,i'm thinking voltage drop (ignition switch maybe?)

Ade.
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1983 924 N/A

[Ozzie]

I had a similar problem with a faulty fuel pump relay.
An intermittent fault and a shit to find.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[Rich H]

What does the battery voltage drop to during crank?

That is a measure of how healthy it is, it is that voltage that has to create the sparks for start and so on, if the battery is sick it will give 8V or less which is not enough. A healthy battery should give 10V or more on crank.
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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[924guy]

take your battery to autoparts store or a shop and have it load tested first, to ensure it really is "good." then you can move on from there. Id certainly look at rewiring the radio as well, by running a new 12v relay with direct main power and activated by the "key in" acc. wire. I would also run a direct radio ground as well, and add at least one additional ground point to the factory radio harness.
the electrics in these cars were not designed for todays high powered radios, if only the original wiring was used, it can cause some havoc, besides power draw zapping the battery, they can also cause lighting fluctuations and even rough running..beef it up a little if it hasn't been already..
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Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

[Slam]

I read somewhere that CIS needs a strong charge to fire the car, and if the battery's down it'll actually prevent the car from starting. My 924 behaves like this. I put in a new battery and make sure the charge doesn't get too low.
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'84 944 - kid blew motor
'83 944 - resting comfortably. For 12 years
'87 944 - sideswiped by trucker
'80 924 - gone
'78 924 - gone
'77 924 - rusting comfortably

[!tom]

I'm wondering if the ballast resistor is being properly bypassed while cranking.
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78 924 NA
5-lug