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496 mag strange intermittent problem

Old 06-19-2022, 03:13 PM
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Default 496 mag strange intermittent problem

please help if possible 496 mag intermittent problem, while driving the boat starbd motor starts to run crappy , black smoke, lower rpms than other motor, if i shut off motor then the battery and wait a sec it seems to reset something, then engine runs fine, seems like an overfueling problem, stuck injector? idk one thing i noticed was when this condition is happening when you turn the key on fuel pump should prime for a few seconds then shut off , while in this condition it never shuts off. any help is appreciated.
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Old 06-19-2022, 04:32 PM
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Originally Posted by bobz71 View Post
please help if possible 496 mag intermittent problem, while driving the boat starbd motor starts to run crappy , black smoke, lower rpms than other motor, if i shut off motor then the battery and wait a sec it seems to reset something, then engine runs fine, seems like an overfueling problem, stuck injector? idk one thing i noticed was when this condition is happening when you turn the key on fuel pump should prime for a few seconds then shut off , while in this condition it never shuts off. any help is appreciated.
Fuel pump doesn't shut off. That is different but when the motor is running the fuel pump will not shut off.
Check fuel pressure and need to scan for codes
Also could use your motor serial number?
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Old 06-19-2022, 05:25 PM
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yes i know it doesnt shut off while running , i shouldve specified that not while engine is running but when i turn on key to prime the system before i crank motor the pump will just keep running, seems like something is just causing fuel to dump in and not combust i will try to scan for codes and i will check fuel pressure asap. serial number M 025579 496 mag. thanks for any help
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Old 06-19-2022, 07:01 PM
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I'm thinking the injector driver but need the scan to verify
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Old 06-20-2022, 07:29 AM
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ok i should be getting it scanned tomorrow, i hope, i will let you know asap.
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Old 06-20-2022, 07:36 AM
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also is the injector driver an internal part of the computer? just curious?
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Old 06-20-2022, 08:27 AM
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Originally Posted by bobz71 View Post
also is the injector driver an internal part of the computer? just curious?
Yes, it's internal to the ECM
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Old 06-22-2022, 07:52 PM
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so havent had it scanned yet, waiting on adapter for the 496 then ill see, thanks again Bob
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Old 06-23-2022, 01:01 PM
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so i switched computer from working good motor to running bad motor, did the same problem to the original running bad motor thus i believe ruling out a computer issue. also test pressure at rail turn key on 43 psi, then slowly drops then start motor stays steady at 36ish psi both motors do exactly the same numbers.
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Old 06-23-2022, 01:10 PM
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As far as fuel pump staying on, i would suspect relay first ? I think.
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