Thanks Chris. I have tried undoing the shift interrupt off coil (takes that out of equation, no)? Will check the w/r on sensor in morning when at boat. I will probably go through the whole troubleshoot from start.
So I checked for voltage on lead and had 12v.How Mercruiser Thunderbolt ignition systems work.
Mercruiser Thunderbolt ignition systems. Mercruiser introduced the Thunderbolt IV onto their engines in 1982, alongside the introduction of the 1-R drives. The TB-IV system was used until the introduction of TB-V mid-way through 1996. Thunderbolt V was an improvement on an already exceptionally...forums.iboats.com
yes
I really don't feel like drawing another big arrow on the next step ...
Brutal!
It was a pretty big arrow.Unless I an doing the gap test wrong, not getting spark. Have already changed coil. No freaking spark!!
All good. Did go through the chart already. No spark on coil lead. Not sure I am doing it correctly. Waiting on a spark gap tester. Been using an old plug
An old plug will work fine.
Not sure what the "spark gap test" is. The next step where you rapidly ground the green/white wire bypasses the ignition sensor.
The flow chart says put a spark gap tester in the coil wire off distributor from coil. Am I supposed to use the G/W wire from HEI or the terminal on the sensor?
Spark gap tester in. Remove the white/green wire from the sensor and rapidly touch it on and off ground (at least 3 times per second)...
Well tried with gap tester and nothing happened. Do I now assume its TB
If you did the test correctly and there's no spark, next step is replace the coil (rarely bad), and if that doesn't work, replace ignition module (very rarely bad). Ignition sensor is the most common fail point, so make sure you're testing correctly. I also saw a post advising you to reconnect the tach wire (even though you said it was bare). Hopefully you didn't do that and have been testing with the wire disconnected. Actually though, looking at that last step: as long as you're getting 12v to the coil pos, you should be able to generate a spark by disconnecting everything from the coil neg, attaching a jumper lead to that and grounding it rapidly. (Or I guess you could attach a scope to the neg and see if the module is actually switching the ground... But that's a bit fancier than needed)
I've been disconnecting the W/G from the sensor not the coil neg and attaching ground to sensor. Will try next chance I get. I have already ordered a sensor after hearing the module rarely fails. Thanks again and will let you know how it turns out. I live where parts arent readily available.
Are you in Australia too?
