Umm, so I'm crap with electronics.

I have a pertronix type installation and have wired it in accordingly and installed a GT40 Bosch coil (yes just the GT40 type - no R or T after the 40) minus the resistor (the white ceramic block about the size of a AA battery)- I am getting no spark on the plugs but when I remove the main cable from coil to dizzie, it produces a spark in expected rythm with the hall sensor picking up the 4 90 degree triggers.

So, I've changed dizzie cap, cables and spark plugs. No dice.

Anyone got any pointers? Even if I put the spark plug on the end of the main coil lead there is no spark?!?

I think I may have an intermittent ignition switch problem, do you agree? The ignition barrel isn't particularly tight and the car is rough as buggary so I wouldn't be surprised if this is the case.

Also changed the rotor but still no spark.

That's a doosey! Does the coil lead fit properly on the coil? I'm guessing you changed the parts with all new ones. I wonder if the carbon button in the dizzy is touching the rotor properly?

You can isolate the ignition switch by hot wiring it just to test. That'll at least rule that out. Just run a lightish cable from the battery to coil +ve (light so it'll burn out if something is wrong).

I'd be suspecting the cap or coil lead or the connections to them.

Is there a wire that is supposed to be insulated from, but may be earthing on the distributor body?

What kind of spark are you getting? A white thin spark won't power a spark plug, maybe not even jump the gap from rotor to cap.

You should get a big fat yellow or big fat blue spark.

BTW, GT40 is a 3 ohm unit. So be sure to connect both wires from the 1200 harness to the coil+ terminal. These are the two wires that connected to the ballast resistor.

The spark I thought was quite weak, it is there but weak I guess.

Thanks for the ideas and info guys, I will take some pictures tomorrow and upload them after I have another look at the wiring.

Yikes. One terminal has many different wires going into it. There are the two from the ballast resistor (white-black combo) a bundle of wires from the main harness and of course the positive from the distributor.

Is this making logic in your mind ddgonzal? Here are before and after shots.

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  Old Coil.jpg (144.35 KB)


  New (old) Coil.jpg (172.14 KB)

HAD SIMULAR PROBLEM RECENTLY CHANGED EVERYTHING WHEN GOING FROM POINTS TO ELEC YOU DONT NEED BALLAST RESISTOR ANYMORE
JUST USE THE MAIN POWER WIRE FROM HARNESS STRAIGHT TO POSATIVE ON COIL ALSO SHOULD BE ELECTRONIC IGNITION COIL NOT POINTS COIL AS THEY NEED HIGHER SPARK
MAKE SURE DIZZY IS EARTHED I RAN LEAD FROM DIZZY TO BODY

TRY TAKING DIZZY OUT AND ROTATING BY HAND WITH IGN ON SEE IF YOU GET SPARK THEN
THATS WHAT I HAD TO DO AND ITS ALL GOOD NOW

Chris, do you have a test lamp? Even a multi-meter will do if it has a continuity option. See circuit diagram for pertronix installation. Looks like you have +12V to both sides of the primary winding of the coil.

The splade that has the blk/red trace and blk/white trace goes to the + coil terminal. The blk/red trace wire is there to supply +12v during cranking so that a nice big fat spark is availble. Normally there is only ~ +9v to the + coil terminal via the black/white trace wire to increase the lafespan the of the no longer installed points.

The two single spade blk/white trace wires that used to go to the ballast resistor need to be joined together or reinstall the ballast resistor. If the wires are joined together the coil will see +12V all the time or with the ballast resistor it will see +9v once the engine has started and teh starter is no longer engaged.

The black single spade wire that went from the -ve side of the coil to the distributor body can be disconnected as you now have the -ve [black] wire from the pertronix unit connected directly to the -ve side of the coil.

Yes, ensure both wires are attached to the Coil + terminal

BR - cranking 12V
BW - non-cranking 12V

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