924Board.org

briankienle · Joined: 22 Sep 2006 Posts: 14 Location: Bremerton, WA

New poster here. I have a 1977 924 that cranks, fuel is getting to the engine but won't spark. Seems like the issue is a the coil. I had it checked and it checked out (even pulled another that I know works and same deal.) when I check for spark at the coil wire there isn't any. voltage is reaching the coil (through 2 resistors, one ballast type and another plastic one), even tried bypassing the resistors to see if it would spark, nothing. checked the ground, even grounded it directly to the block. no luck. Any ideas? I must be missing something!
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Brian in Bremerton

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Welcome to the board, Brian.

Does your car have the old-style contact breaker ignition or the electronic type?

If the former, there's not much to go wrong so long as everything's adjusted OK (contact gap/dwell angle, etc); if the latter, check the voltage/wiring at the control box (behind the left headlamp).
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

briankienle · Joined: 22 Sep 2006 Posts: 14 Location: Bremerton, WA

I swapped out a working ignition control box from a parts car I have and same result, no spark. Is there a relay that could be the root of the problem?
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Brian in Bremerton

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Well...you could check that the ignition box is getting power. I don't think there's a relay for this - it comes directly from the ignition switch.

Secondly, what about your distributor? If that isn't supplying the timing signal to the ignition box, you won't get a spark. And don't forget to check for broken wires/loose connections.

Do you have an alarm/immobiliser? These can do funny things with the ignition wiring.
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

chris24 · Posted: Tue Oct 03, 2006 6:44 pm Post subject:

Seconded. If you swap in a known good distributor, that would help narrow it down.
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1983 - 924 (185K miles) - not mint
1985 - 924 (148K miles) - mint
1990 - 944S2 cab (52K miles)

924RACR · Posted: Tue Oct 03, 2006 9:59 pm Post subject:

You ought to also check the coil for resistance itself - believe there is a procedure in the Haynes manual.

Recently had an odd case diagnosing a non-starting racecar (924) where it turned out the tach had developed an odd short preventing the car from starting or running. When cranking, the voltages at the coil were bouncing around in an odd way. After removing the tach lead wire from the coil, the car fired right up immediately on 3 cylinders! (one lead was removed and plugged into an external/spare spark plug to monitor for spark).

Pretty bizarre. We ran it without the tach connected; either the tach itself died, or the wiring to it was suspect. But that's not necessarily your situation...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

briankienle · Joined: 22 Sep 2006 Posts: 14 Location: Bremerton, WA

It may be the tach short, last time we were cranking it it did bounce around. Which lead would be the tach (Red or Black?) I did check the resistance, it was right and I do have a good distributor in there. I really appreciate all the feedback, this is a great resource!
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Brian in Bremerton

924RACR · Posted: Wed Oct 04, 2006 12:59 am Post subject:

I'm not sure what the tach was doing in our case, we weren't watching it. But which lead, it was the green one in our case I think. YMMV, as you will likely have different wiring schematics. Not abnormal that the tach might bounce, though.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

briankienle · Joined: 22 Sep 2006 Posts: 14 Location: Bremerton, WA

I plan on swapping the distributor with the working one and we'll see what happens next. Thanks for all the pointers!
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Brian in Bremerton