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Gary
Member
Username: gary_j
Post Number: 6
Registered: 06-2009
| | Posted on Tuesday, June 30, 2009 - 11:34 am: | 
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My 1973 9.8 is not firing, (no spark @ plugs) what can I troubleshoot to pinpoint the problem. Thanks |
Graham Lamb
Senior Member
Username: galamb
Post Number: 5508
Registered: 05-2007
| | Posted on Tuesday, June 30, 2009 - 12:36 pm: |
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Gary, that model has an early Thunderbolt 2 ignition system.
So it still has points and a condenser (which Merc called a capacitor in some reference material) as well as an early stator that incorporated both a low speed and high speed coil (mounted as two separate parts on the stator assembly which was a modular design - kinda neat to see the precursor to the modern stator like that).
The points for these are still available (at a touch over 100 bucks for the pair) but the condenser and high speed coils have been long discontinued.
You can test for continuity between the wires coming from the coils (the ones under the flywheel) - you are basically just looking to make sure the windings are intact.
Be careful to disconnect the wires from the capacitor, and be careful in general if you are fiddling with the capacitor - if it's working it holds a charge of approx 1000 volts - it won't kill you but she bites pretty hard if it discharges when you have a hold of it.
You can also check for simple continuity across the two little posts on the spark plug coils, again just making sure the winding is intact, but it would be unlikely that both went at the same time.
Your issue most likely rests in the capactior (condenser) or the low speed coil itself...
In 1974 this model converted to the Thunderbolt 4 ignition which is still considered "modern". If your model does have an issue involving one of the discontinued parts you may be better served to try and find a complete used ignition from a slightly newer model and retrofit it.
The discontinued parts may still be available from a recycler or a place like www.oldmercs.com but could end up costing you a small fortune. |
Gary
Member
Username: gary_j
Post Number: 7
Registered: 06-2009
| | Posted on Tuesday, June 30, 2009 - 03:43 pm: |
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Thanks for the info, I'll keep my fingers crossed for the cheaper fix. |
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