cutting out....

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green67cuda

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ok...on the way back from the dragstrip tonight (first time in this car....more on the night later) the car started sputtering a lot....it did it on one of my runs too, and i have been noticing it in the past few weeks, but tonight it was REALLY noticeable.

I was cruising along at 4K, and the tach started spiking downward....it would tick down to 3K, randomly, but often...then it'd be fine for a few minutes...then start again....then it started pegging zero, and my girlfriend called (she was following me) and said i was shooting fire out the tailpipes....

now, i have a truck that had a bad coil about 6 years ago, but it would just drop to zero and sometimes start back up, and sometimes not.....
the barracuda, however, has a Mallory hyfire IV box and the matching coil....i don't think it's the coil, because the tach is dropping (on the truck, the tach comes off the - coil wire, and on the cuda, it comes off a tach lead from the box)

any thoughts??
 
Before condemming the ignition box check for loose connection to the coil or ignition module also check the gang plug on the firewall for a bad connection
 
done.....
oh....and the dizzy is a mallory YL-577HP....has the optical trigger and mechanical advance
 
Check for bad grounds. Do you have one from the block to the body ?
 
actually, adam...you reminded me......
when i was reconnecting everything when i put the engine back in, the ground wires for the dizzy and for the hyfire somehow got wrapped around the alternator stator wire, and were connected there.

When i went to connect the battery, i got a nice big spark, checked everything, tried to connect again, got a spark again, then investigated everything that was disconnected during removal and found the wires.....then grounded them....

and, i also realize that this has been happening since i got it all back together....when i accelerate, i have noticed the tach bobble a littleall the way through the rpm range....so i MUST have fried either the box or the optic module....
 
i found Mallory's test procedure for the unilite module....

after proper preps, should have normal voltage on coil (-), then when you block the beam in the module, it should drop to <2V.
mine only droped to 4.5, which the procedure says that it could produce a weak spark....so maybe that's NOT the problem...i ordered a new one anyway, because 4.5V isn't right anyway.
 
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