ignition problem
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ignition problem
i have a 78 f150 with a 74 351c.until recently no problems with how it runs.it developed a high rpm miss.today it just up and died.replaced coil module and battery.only get fire from coil when i first hit key then no spark.anyone ever have this happen before.any ideas besides burning it lol
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
This means the module is not switching the coil on its own. Either the pickup in the distributor is bad, the ignition module is bad, the wiring in between the module and the pickup is bad, or the module is not getting power.
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
If the engine is cranking at all, you're getting power to the solenoid which means the fusible link is fine.
To check the pickup, disconnect the distributor and measure the resistance between the ORANGE and PURPLE wires coming from the distributor; it should be between 400 and 700 ohms. Neither wire should have continuity to ground.
To check the pickup, disconnect the distributor and measure the resistance between the ORANGE and PURPLE wires coming from the distributor; it should be between 400 and 700 ohms. Neither wire should have continuity to ground.
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MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
You've eliminated the pickup, now move on to the other things I told you.
That voltage is too low; it should be 6 to 7 volts in RUN and 10 or so in START. What voltage do you get across the battery posts?
That voltage is too low; it should be 6 to 7 volts in RUN and 10 or so in START. What voltage do you get across the battery posts?
Senior User
Joined: Dec 2008
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From: Fowlerville, Michigan
Before you bust out the multimeter though, take a look at your duraspark module - if there's epoxy running out the back of the module onto your fender apron, odds are it's toast. I fried a few in the past by not using the correct ballast resistor with my coil.
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i have verified power to module i ran a continuity test on the wires none broken.cleaned all connections and in run position have around 7.5 volts to coil and little over 10 cranking.thanks for all your help fmc400
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