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03-28-2024, 02:04 AM | #21 |
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Join Date: Jun 2014
Location: Land of Lincoln
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Re: Model A no spark
Until you fix the loss of power in the fuse holder your spinning your wheels. The starter mounted fuse holders are know for going bad. Replace it or bypass it, originally A’s didn’t have fuses. I would go to a automotive parts store and get a inline fuse holder and bypass the starter holder, that way if you have other issues you won’t burn your car up.
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03-28-2024, 07:02 AM | #22 |
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Location: Western North Carolina
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Re: Model A no spark
The Hammer is right. I had to clean the contacts in my fuse holder and bend the contacts for better contact. I changed over to a 30 amp circuit breaker that fits into the fuse holder. I carry extra fuses just in case the circuit breaker fails. I use some copper containing electrical grease for contacts such as in the fuse holder. That greatly reduces the chance of oxidation of the metals.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
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03-28-2024, 07:34 AM | #23 |
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Join Date: Sep 2022
Location: Canton, Michigan
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Re: Model A no spark
You could get one of these to replace that fuse holder:
https://www.amazon.com/JACAWEEN-Wate...aaebfdd1b40ce6
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--------------------------------------- 1929 Model A Tudor "Stay away from negative people, they have a problem for every solution" Model A Ford Club of America Model A Restorers Club Motor City A's Club |
03-28-2024, 08:55 AM | #24 |
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Join Date: May 2010
Location: Southwest Ohio
Posts: 35
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Re: Model A no spark
[QUOTE=Amctavish77;2300669]I have voltage on either side of the fuse with the key in the off position but lose voltage when the key is in the on position./QUOTE]
Try putting paper between points and test with ignition on and see if you have power. If your getting power at junction box then the fuse is good. |
03-28-2024, 11:59 AM | #25 |
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Location: Central Illinois
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Re: Model A no spark
Unless I'm confused: The comments don't make sense to me. With open/insulated points you should get 6+ volts at all test locations of the primary ig circuit this includes the points arm. Are you keeping track of the ignition switch status? It must be closed / 'on' , points open / insulated to have the correct readings.
With ig switch 'on' points closed, the input side, - coil post should be 6+volts. But the output side, + coil post, red wire should have zero or nearly zero voltage reading if a digital meter is used. The reading at the points arm should also be 0. If these two readings are still 6+ volts then the points are not fully closed or are contaminated at the contacts or there is a ground issue at the distributor or further on. Placing a jumper across the terminal box posts will by pass a problem that exists between the passenger post, up to the ammeter and back to the driver side post if the problem is an 'open' in that portion of the ig circuit. If the problem is an unintended ground / short, the jumper will not work. When you tested the voltage readings at the safety fuse and got zero with the ig switch 'on' and 6+ volts on both sides with it off, is this reading repeatable? We assume you are using a VOM placing the black lead on the fuse holder and the red lead on a good ground such as a clean head nut. If you put the leads on each end of the fuse holder, you might see a 0 volts or a small fraction to the right of the decimal. Analog meters won't show the fractions. If your car is wired to Ford specs, the ig switch being on or off should not affect the voltage readings at the fuse holder. If you car has a hot rod mod where the ig switch is wired in between the starter switch stud and the input side of the coil rather than between the coil primary winding output side and the distributor points as Ford intended, then your readings as written might indicate an intermittent grounding of the switch. This is a common issue. The zero readings at the sides of the safety switch would not allow 6+ volt readings further up the line. It seems they are intermittent??? A law of DC auto electrics is that "all voltage is consumed by the load/s of a completed circuit". The only loads between the - negative battery post and the output side of the starter switch safety fuse should be insignificant resistances at the connections. There are no meaningful loads, such as the primary ig coil windings ahead of the safety fuse. I'm using "Modern electron flow" in my analysis which states that current / electrons flow from the - post / anode to the + post / cathode.
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"It ain't what you know for certain that gets ya in trouble. It's what ya know for certain that just ain't so!" Last edited by Rob Doe; 03-28-2024 at 12:04 PM. |
03-28-2024, 07:01 PM | #26 |
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Re: Model A no spark
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03-29-2024, 09:11 AM | #27 | |
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Join Date: Mar 2024
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Re: Model A no spark
Quote:
Your 28 A model won't start, with no spark even after trying a known good coil and new wiring; you're seeking help to identify and resolve the issue. |
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03-29-2024, 09:27 AM | #28 |
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Join Date: Feb 2020
Location: Paducah Ky
Posts: 282
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Re: Model A no spark
You probably have a very poor connection somewhere, probably the switch or a ground. Try bypassing the switch like someone suggested, with a jumper directly to the battery, or to a known good connection like the starter.
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