Low voltage from ignition module mercruiser 5.0 thunderbolt

Toreh

Cadet
Joined
Jul 24, 2019
Messages
7
Hi i got some problems with no spark,i have measured the red/white from the ignition module and only get about 11.55 volt out -in i have about 12.65v betveen the black and grey in the socket for the module-does this mean that the module are broken?
btw i tried the module in å similar boat and it did not start-does that seal deal?🤔
 

wellcraft-classic210

Master Chief Petty Officer
Joined
Sep 22, 2010
Messages
839
Hi
A few questions

Does the engine start for you ? ( if not have you verified their is no spark ? )

Whats the voltage at the battery when cranking the starter ?
 

Toreh

Cadet
Joined
Jul 24, 2019
Messages
7
Hi the engine starts sometimes and only runs for about 2min,sometimes spark sometimes no spark,voltage on batteri are 12,today i change the alternator and batteri-still the same,i will buy me a new ignition module and try again
 

Toreh

Cadet
Joined
Jul 24, 2019
Messages
7
Before i changed alternator and batteries the batteri voltage when crancing was about 11.7v
 

wellcraft-classic210

Master Chief Petty Officer
Joined
Sep 22, 2010
Messages
839
Hmmm


Its not surprising that the voltage would drop a little on startup given the current draw-- but I don't know the typical values or more importantly min. limits for ckt operation.

If the engine starts sometimes it would seem a connection is the likely cause // or perhaps something that's failing when it gets warmed up.

It would seem that you either have a voltage supply issue from the key circuit // or an intermittent failure from ignition system connections or failing components.


1 Suggestion - bypass the key voltage to coil supply circuit with a PROPERLY FUSED wire directly from you battery to your coil a way to determine if its upstream (key supply ckt ) or downstream ( ignition )

If the jumper wire works be sure to inspect the 10 pin connector ( engine harness plug ) as part of your checks on the key ckt for the root cause.
 
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