1990 454 mag lost power

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10-16-2022, 10:30 AM

#11

phragle

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Quote:

Originally Posted by Prestigeworldwideee

Guessing my next move to replace the distributor and rotor?

Look like the one I should buy?:

A.A Tune-Up Kit Distributor Cap Rotor for MerCruiser GM V8 Thunderbolt IV, V, HEI Ignition System 18-5273, 805759Q3 https://a.co/d/iQcMcER

Im guessing your next move is to slow down and develop some trouble shooting skills. A harbor freight test light goes a long ways and they start at like $3.99

https://www.electricaltechnology.org...lor-codes.html

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liberator221 (10-16-2022)

10-16-2022, 10:49 AM

#12

GPM

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Maybe,

Amazon.com: B. Ignition Sensor Kit for MerCruiser Thunderbolt I IV Distributor : Automotive

10-16-2022, 12:02 PM

#13

Prestigeworldwideee

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Quote:

Originally Posted by GPM

Could be the module in the distributor

How do I test that? Pop the distributor cap off, use a light tester and the battery negative?

Last edited by Prestigeworldwideee; 10-16-2022 at 12:41 PM.

10-16-2022, 12:56 PM

#14

Griff

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TB IV ignition troubleshooting flow chart https://bpi.ebasicpower.com/faq/MERCSB92-11.htm

10-16-2022, 01:07 PM

#15

Prestigeworldwideee

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Quote:

Originally Posted by Griff

TB IV ignition troubleshooting flow chart https://bpi.ebasicpower.com/faq/MERCSB92-11.htm

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.

10-16-2022, 02:36 PM

#16

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Okay.
turn key to run. Put your volt meter to the ignition coil leads. Is there 12 volts present ?

10-16-2022, 04:02 PM

#17

GPM

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From the looks of that distributor, you may want to replace it.

10-16-2022, 04:07 PM

#18

Prestigeworldwideee

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Quote:

Originally Posted by SB

Okay.
turn key to run. Put your volt meter to the ignition coil leads. Is there 12 volts present ?

Just pull a spark plug wire off and crank it over?

Last edited by Prestigeworldwideee; 10-16-2022 at 04:20 PM.

10-16-2022, 04:48 PM

#19

GPM

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You already know you don't have spark, you just don't know why. Call your local auto parts store and see if they can test your module.

10-16-2022, 05:07 PM

#20

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Quote:

Originally Posted by SB

Okay.
turn key to run. Put your volt meter to the ignition coil leads. Is there 12 volts present ?

Quote:

Originally Posted by Prestigeworldwideee

Just pull a spark plug wire off and crank it over?

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 -.

Last edited by SB; 10-16-2022 at 05:11 PM.

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