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post #1 of (permalink) Old 12-06-2002, 06:39 PM
sirhumpy
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No spark, fried module?

I've got a completely new motorcraft electronic ignition system as well as new wiring. I fired it up this morning and it ran for about 10 seconds and then died. Turns out I don't have spark any more. I did some searching and installed the ballast resistor and replaced the coil, figuring the excessive voltage killed it. Still no spark. I am getting 12 volts at start and 7 in run at the coil. I'm going to take the module to napa in the morning to have it tested, but my question is twofold: If i can eliminate the coil and all ignition wiring as problems, what else could it be aside from the module? I read about testing the resistance across the dist pickup, but do those go out after 1000 miles or so since i bought the distributor? Secondly, if the module is indeed gone, would it have been caused by the absence of the ballast resistor, or from bad diodes in the alternator? I just don't want to slap another module in there if whatever is killing it is still lurking around in there. Any insight would be greatly appreciated.
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post #2 of (permalink) Old 12-06-2002, 07:38 PM
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Re: No spark, fried module?

Ask and ye shall receive, ignition system consists of:

The crankshaft turns the camshaft,
the camshaft turns the distributor gear,
the distributor gear turns the distributor shaft,
the distributor shaft turns the rotor and the hall effect switch vane.
the hall efect switch vane causes the hall effect swtich to pulse
the ignition module amplifies the pulse,
the pulse is what creates the field for the coil,
the coil creates the energy and sends it to the rotor in the distributor,
the rotor sends the energy to the distributor cap plug wire tower,
the plug wire tower transmits the energy to the spark plug wire,
the spark plug expends the engergy when it jumps the spark plug gap to ground.

The absense of the ballast resistor, or resistor wire applies full voltage to the coil and burns out the coil, often destroying the ignition module in the process.

Ok.. there's the whole thing in a nutshell [img]images/graemlins/grin.gif[/img]
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post #3 of (permalink) Old 12-07-2002, 01:16 AM
sirhumpy
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Re: No spark, fried module?

Thank you LEVE, I guess the two just went out. I'll go pick up another module in the morning and see how things go. Thanks again.
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post #4 of (permalink) Old 12-07-2002, 08:19 AM
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Re: No spark, fried module?

Sorry, I missed the part about a bad diode in the Alternator...

1. Yes, this can have an affect on the ignition module.
2. If you're taking in the igniton module for testing... take the alternator too!
3. Have 'em check the regulator diodes, or watch or AC on the machine as it's being tested (if they can see it!).
4. A bad diode can cause all sorts of nasty stuff in other descrete electronics installed in the Jeep, stereo's blow, etc..
5. Good point! Again, sorry I missed it [img]images/graemlins/blush.gif[/img]
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post #5 of (permalink) Old 12-10-2002, 12:25 AM
sirhumpy
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Re: No spark, fried module?

I took the module and alternator in to be tested and the module was shot, as you predicted. However, the alternator showed good charge but they couldn't give me a straight answer on the diodes, i'm not so sure if they knew how to use the machine aside from checking for charge. What exactly is a characteristic of a bad diode assembly?
post #6 of (permalink) Old 12-11-2002, 12:56 AM
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Re: No spark, fried module?

Symptoms of a bad Regulator Diode are:

1. With a voltmeter set to AC,
a. On a small scale,
b. Measure AC volts at the alternator output cable or wire.
c. Over 0.5v AC and a diode is bad.
2. Increased alternator whine on the radio/cb, etc..
3. Charge warning lamp comming on with no drop in voltage, even intermittenly.
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