XJ40 ( XJ81 ) 1986 - 1994

Fyi: Fuel fail 24

 
  #1  
Old 03-15-2019, 02:55 PM
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Default Fyi: Fuel fail 24

My car died and the VCM code showed FF24. However, the symptoms on trying to restart the car did not indicate a problem with the Ignition Amplifier (Module). Just to be sure, I replaced the ignition amplifier with a new one and the same problem exist. I cleared the code and tried restarting the car. problem still exist.
Going with my prior experience and the symptoms present, (the car tries to fire up, and would backfire through the intake. After many tries, it started and would idle for about 30 seconds and die.
Replaced the Mass Air Flow sensor and now its running fine. Put back old Ignition Amplifier and it is running fine.
What's up with that?
 
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Old 03-16-2019, 12:28 AM
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There’s gotta be an intake leak, at least that was my experience with intake backfires.
 
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Old 03-16-2019, 08:53 AM
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Originally Posted by sanchez View Post
My car died and the VCM code showed FF24. However, the symptoms on trying to restart the car did not indicate a problem with the Ignition Amplifier (Module). Just to be sure, I replaced the ignition amplifier with a new one and the same problem exist. I cleared the code and tried restarting the car. problem still exist.
Going with my prior experience and the symptoms present, (the car tries to fire up, and would backfire through the intake. After many tries, it started and would idle for about 30 seconds and die.
Replaced the Mass Air Flow sensor and now its running fine. Put back old Ignition Amplifier and it is running fine.
What's up with that?
Hi sanchez,

FF24 doesn't necessarily indicate failure of the ignition module/amplifier, but rather a problem with either an open or short circuit in the wiring to the module. A likely explanation is that there was an open circuit between the harness connector and module due to oxidation on the connector terminals that triggered FF24, and by swapping modules you resolved the problem by scraping through the oxidation. Just to be safe, it would be good to go back and flush the electrical connector with zero-residue electronic cleaner. It doesn't take much oxidation to add sufficient electrical resistance to a sensitive sensor circuit to push it out of the range expected by the Engine Control Module. The humidity and salt air in Florida are not friendly to electrical connections.

The same situation may have existed with the MAFS connector but it had not yet triggered FF12, and you likewise resolved it by swapping the MAFS.

This is a great reminder to all of us to periodically clean the electrical connectors of important Engine Management System components and to also clean the engine bay ground points, especially the ones referenced by the EMS, two on the intake manifold and one on the firewall behind the cylinder head.

Cheers,

Don
 

Last edited by Don B; 03-16-2019 at 09:04 PM.
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  #4  
Old 03-16-2019, 10:07 AM
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Exactly my thoughts Don, but you said it much more eloquently than I could have!

Larry
 
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Old 03-19-2019, 05:50 AM
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Considering the circumstances, I will agree with Don. Corrosion, even minor is a PITA.
Thank you all.
 
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