924Board.org

stenakt · Joined: 27 Oct 2008 Posts: 2 Location: Oakville, Ontario

I recently had a problem with starting the 924 (1980). No spark, so checked the power to the coil and nothing. I 'hot wired' from the battery to the +ve teminal of the coil and it started immediately. The problem then disappeared, but comes back now and again. Hot wiring makes it go away for a while every time.

From searching other posts I reckon that it is either
1. The ignition switch
2. The ignition module
3. The fuse box

and the Haynes manual is on it's way! What I can't understand though is why a quick hotwire (which I remove once running) makes the problem go away?

Also, why are there two feed wires to the positive side of the coil?

thanks for your help

Stewart
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1980 924, absolutely stock
1991 944 S2, stock

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

Welcome to 924board.org Stewart.

Sounds like your problem may be a faulty ignition coil ballast resistor or a connection associated with the coil B+ supply. IIRC there should be 2 ceramic resistors, one in series with coil + and ignition on and the other in series with the connection at the starter for power during cranking. Check for a nominal 12V at the coil (could be as low as 6V) both with ignition on and during cranking.

Rich H · Posted: Tue Oct 28, 2008 8:33 pm Post subject:

My 1980 NJ/A has resistance wires not resistors, they have a sort of clear orange insulation with a black/purple stripe on them.
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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

924RACR · Posted: Tue Oct 28, 2008 9:36 pm Post subject:

The power for the coil is supplied through the ignition switch.

By hotwiring the car, you bypass the ignition switch and supply your own.

Since this works, you have replaced the faulty component. Now you just need to get the proper new switch to install.

A switch is a mechanical device, not just electrical. As such, there is wear associated with it. Of course, since this appears in our FAQ as a recommend diagnosis step, that also points out that failure of this device is common, at the current age of our cars.

Added info; when cranking, the coil is supplied 12 V via one circuit (and a ballast resistor or load wire, depending on the year of the car), whereas when running a different circuit supplies power to the coil at only 6V. This allows creation of a spark twice as hot as normally needed to support starting a cold engine.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

IIRC the circuit during cranking comes off the starter. May want to check there for loose connections.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

michi924 · Joined: 22 May 2007 Posts: 163 Location: Pontevedra, Spain

If your car has ballast resistors, check it for possible failure.
I it doesn't has ballast ressitors, check the conection from the coil to the starter. (pin 16 or 15a in Haynes manual).
You should have more than 5volts (5-7 volts) in the coil +terminal with the ignition on (but not cranking) and 12v while cranking.
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Porsche 924 NA Euro.

stenakt · Joined: 27 Oct 2008 Posts: 2 Location: Oakville, Ontario

Thanks for the welcome and thanks everyone for your replies - given me a few things to look at. I'll post the solution when I find it..

Stewart
_________________
1980 924, absolutely stock
1991 944 S2, stock