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1990 454 mag lost power

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Old 10-16-2022, 08:03 PM
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Bump the engine over and make sure the distributor is turning.
SB is trying to walk you through this, follow him.
With key in run position you should have 12v at positive post of coil. Voltage goes through coil and out negative post and on to ignition module. When engine turns over the ignition module turns that negative side off and on which makes the coil fire.
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Old 10-17-2022, 05:51 PM
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Originally Posted by Prestigeworldwideee
I don’t have many diagnostic skills, there’s a spark on the outside of the distributor cap that connects to the ignition module. I tried touching my light testers to everything inside the distributor cap and got nothing.
If you don't have the skills to follow the flow chart I posted, then you really should just have a professional diagnose the problem.
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Old 10-18-2022, 05:13 PM
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Originally Posted by SB
Please reread above.

Furthermore….your coil looks like this.
Looking at carburetor from frt of engine, it is just behind the carb to the right.Puple wire terminal is + and grey wire terminal side is -.


No, there’s not.
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Old 10-18-2022, 05:43 PM
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Originally Posted by Prestigeworldwideee
No, there’s not.
There is a coil somewhere. Maybe further back. Easy to find if you Follow the ‘spark plug wire’ attached to center of distributor cap. This goes right to the coil. And why it’s actually called the coil wire.
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Old 10-18-2022, 07:22 PM
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Originally Posted by SB
There is a coil somewhere. Maybe further back. Easy to find if you Follow the ‘spark plug wire’ attached to center of distributor cap. This goes right to the coil. And why it’s actually called the coil wire.
I mean to say there is no voltage coming out of it.
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Old 10-18-2022, 07:44 PM
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Originally Posted by Prestigeworldwideee
I mean to say there is no voltage coming out of it.
Double checking
key to run ?
+ lead of multimeter to purple wired connector on coil ?
- lead of multimeter to a good ground on engine ?
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Old 10-18-2022, 08:08 PM
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Originally Posted by SB
Double checking
key to run ?
+ lead of multimeter to purple wired connector on coil ?
- lead of multimeter to a good ground on engine ?
Yep…. Needle didn’t move one bit.
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Old 10-18-2022, 08:24 PM
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Okay.

Turn key to run. Get to back of ignition switch.

+ lead multimeter to purple wire connection.
- lead multimeter to the ground post or bar the guages or etc ground to.

Do you have 12 volts at the ignition post (purple wire is connected to it) of key switch ?
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Old 10-19-2022, 05:07 PM
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Originally Posted by SB
Okay.

Turn key to run. Get to back of ignition switch.

+ lead multimeter to purple wire connection.
- lead multimeter to the ground post or bar the guages or etc ground to.

Do you have 12 volts at the ignition post (purple wire is connected to it) of key switch ?
There was an orange wire and yellow wire. The orange had 12v, the other one, nothing.

Last edited by Prestigeworldwideee; 10-19-2022 at 07:10 PM.
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Old 10-19-2022, 06:56 PM
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Originally Posted by Prestigeworldwideee
Therw was an orange wire and yellow wire. The orange had 12v, the other one, nothing.
yellow wire with red line is start. Some call it solenoid. This wire attached to ‘S’ terminal back of ignition switch.

Red wire with purple line is power from battery. Terminal on ignition switch is marked ‘B’

Purple wire powers the ignition and things like gauges that are on when engine runs. The Terminal on back of ignition switch fir this is marked ‘I’ for ignition.

Orange , if there, is typically powering other stuff on dash.


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