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Old 07-02-2016, 03:23 PM
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Texasdoc Texasdoc is offline
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Join Date: Feb 2012
Location: Keller, TX
Cobra Make, Engine: Lonestar Classics LS427. Self-built 408W, AFR 195 heads, Performer RPM Intake, Quick Fuel 750, 407rwhp, 479rwtq
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Maybe.... Still trying to hunt down the cause of this. Waiting for the dist Brent sent.

While waiting, I decided to go back thru and check everything again. Even though everything has been checked, why not? Plugs gapped. Spark lead ohms good. Fuel pressure, timing, etc.

I pulled out the old/destroyed MSD cap that I used to set the rotor phase to check it again. Hooked it up and started the motor. Everything looks "in phase" but the spark is barely visible. Hmmm, weak spark.

Put the new coil back in (had replaced it with an old one for testing) and it still had weak spark. Since the plugs are good, wires good, coil good, lets check the Mallory Hi Fire box (6AL copy).

It gets 13 volts on the big red wire (I also have the MSD capacitor on this line to prevent spikes). 13 volts on the small red wire. Ground is good.

Somebody make sure I did this right:
1. Disconnected the coil lead at the distributor, put it 1/4 inch from ground.
2. Disconnected the Green/Purple wires at the distributor.
3. Ignition On, Engine off
4. Short the Green/Purple wires with a paperclip. NOTHING.
5. Disconnect the Green/Purple wires at the connection at the box (I have the MSD shielded cable as an extension). Short these wires - NOTHING.
6. Cut the connector off the Green/Purple wires so I only have a few inches of wires going right into the box. Short these - NOTHING.
7. Touched the white (points) wire to gound - BUZZ. Big spark. Nice loud buzzing.

So, it appears the magnetic pickup input to the Mallory box is dying/dead. Did I do anything wrong in the testing? There is not a switch to tell the box magnetic vs points.

Any other thoughts before I go buy a new ignition box?
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