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  Low Ignition Voltage Help

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Author Topic:   Low Ignition Voltage Help
bobbyford72
Journeyman

Posts: 10
From: new jersey
Registered: Nov 2000

posted 03-20-2001 10:26 AM     Click Here to See the Profile for bobbyford72   Click Here to Email bobbyford72     Edit/Delete Message   Reply w/Quote
Anyhelp from you guys would be appreciated on the following item:
I have a full size ford '72 Ltd conv. w/400 ci engine. I have an aftermarket points conversion kit installed with a high capacity coil. Car had run fine for quite sometime with this setup, now when I take a voltage read at the coil with key off it is 4.5 volts. With car running it measures between 7 and 8 volts. Engine seems underpowered.
I assume I should have anywhere between 9.5 to 11.5 volts when running to properly fire the ignition. Would the low voltage make engine seem to run weak? I assume that all older cars expeirence this problem as they age. What is the best fix? Could the ignition switch be the culprit? Could I wire in a relay between the ignition wire to the coil to bring the voltage back up? Has anyone else had this problem. Any help and diagnostic suggestions would be appreciated.
Thanks again

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SteveLaRiviere
Administrator

Posts: 44935
From: Saco, Maine
Registered: May 99

posted 03-20-2001 11:33 AM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
Bobby, it's not a problem, the ignition wire on the older Fords is a resistance wire and you need to tap into a keyed 12v circuit to power your new Petronix {?} kit. I assume the kit calls for 12 volts?

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'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
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"Keep your driveway all Ford!"

[This message has been edited by SteveLaRiviere (edited 03-20-2001).]

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bobbyford72
Journeyman

Posts: 10
From: new jersey
Registered: Nov 2000

posted 03-21-2001 10:33 AM     Click Here to See the Profile for bobbyford72   Click Here to Email bobbyford72     Edit/Delete Message   Reply w/Quote
Steve, thank you for your response. Just so I am clear on your answer, I should disconnect the wire that runs from the key ignition (resistance wire) to the coil and run in a seperate keyed controlled 12v power source i.e, from the alternator to the coil and then cap off the disconnected ignition wire.
Does sound right?

Thanks again.

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Moneymaker
Administrator

Posts: 26813
From: Lyons, IL, USA
Registered: May 99

posted 03-21-2001 11:08 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Correct Bobby. The factory wire had higher resistance for the breaker style points and condeser igntion system. Just replace it with a full 12 volt source ignition on wire. Welcome to M&M by the way !

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Alex Denysenko Co-Administrator and Moderator NHRA/IHRA/SRA member
Fleet of FoMoCo products
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