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Registered
Join Date: Nov 2002
Location: Clinton, CT
Posts: 51
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confused....cd box/ ign. coil wiring
First a llittle backround. I bought my car 2 years ago, in poor running condition. After taking it to my mechanic one of the problems found was that the previous owner had removed the cd box and changed the coil and added a condenser to avoid buying a new cd box. my mechanic replaced the cd box and coil and rewired things to perform properly. ever since everything has performed just great.
Now to the problem. I am in the process of redoing the engine compartment and engine. Painting, cleaning up wiring and doing an msd ignition. When i went to install the msd my wiring to the ignition coil doesn't seem to be right. The pos. wire goes into the factory harness and to the cd box, but the neg. side is grounded to bolt holding the coil. By looking at the electrical diagrams for the car it looks like that should go to the cd box along with a wire from the distributor. I do have a wire coming out of the distributer that goes to the condensor and that wire has been cut off. Before i change any of these wires around i would like to know how it is suposed to be connected and how to tell if i have the right distributer in the car, why is there a condensor there, isn't that built into the cd box? Thanks for any help you can provide. I like to understand how things work in the car, especialy before i am about to change things around.
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74 911s 2.7 Turbo |
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The condenser isn't needed with a CDI system because the points aren't switching a high current with an inductive load. Significantly less than an Amp is being switched, so no tendency towards rapid points pitting/erosion exists.
The coil is supposed to be grounded at the bracket, but a braided shield was also run from that same ground location ... to the distributor and back to the CDI ground lug 'D' terminal ... as part of the OEM wiring harness! The braided shield may have been omitted by your mechanic when he reinstalled the CDI unit. The system will work without it due to existing grounding, but it adds to the reliability of the factory CDI unit!
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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Registered
Join Date: Nov 2002
Location: Clinton, CT
Posts: 51
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Ok i do have that ground on the cd box, but it must get lost in the harness, because it is not on the other end near the coil. If i understand correctly the car is wired almost correct meaning the 2 wires from the msd, that are suposed to go to the original +/- coil wires should go to the original + and ground and the new wires from the msd will get conected to the top of the new coil. no longer having it grounded to the mount??
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74 911s 2.7 Turbo |
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Registered
Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,140
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the MSD comes with wiring instructions for clarity. If you need a copy e-mail me. Put MSD in subject header.
and fwiw I rewired everything using Radio Shack silver solder. Don't use Radio Shack wire terminals.
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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