How to check Thunderbolt IV module

[RonThom]

I have a 1990 5.0 alpha 1 and it has ran great for years. Now after 5-15 minutes it quits and when I check for spark it is not firing. I have changed the sensor, rotor button, and coil. I have also unhooked the **** interupt switch, no luck. Once it sets for hours or sometimes days it will start and run for 5-15 minutes.<br /><br />Can you check the TB IV module or should I just buy a new one?????<br /><br />thanks

 

[Rickles]

Re: How to check Thunderbolt IV module

I'd be checking the ign. sw.first before you replace the module.You'll need a Merc scan tool to check the module.Check the connectors for corrosion and pin tension also.

 

[RonThom]

Re: How to check Thunderbolt IV module

thanks, ignition switch ok, already checked that. It will crank but no fire after it quits. The plug that goes into the module seems loose to me. I have unplugged it, cleaned the pins and plugged it back in, still no luck.

 

[bomar76]

Re: How to check Thunderbolt IV module

http://www.marinemechanic.com/site/page251.html <br /><br />akriverrat sent me that link when mine went goofy....helped me determine mine was FUBAR

 

[RonThom]

Re: How to check Thunderbolt IV module

Thanks, I have done all of those things, still no spark at present time. Must be TB IV module.

 

[wvit100]

Re: How to check Thunderbolt IV module

That is exactly what mine was doing last spring. It would start and then die as soon as it warmed up a little. It ended up being the module, new module and it ran fine.

 

[bomar76]

Re: How to check Thunderbolt IV module

If you follow the flow chart exactly and it leads to bad module that's what it is.<br />The chart is dead on the money.<br />One thing I discovered when I needed a module is no dealer stocked that item. Is yours the manifold mounted module or the distributor mount?

 

[RonThom]

Re: How to check Thunderbolt IV module

Mine is manifold mounted. Being a Holiday weekend I can find a dealer open to even see if they do have one. Hope to find one tomorrow. Will let everyone know if that fixes the problem.<br /><br />Thanks to everyone for the good info.

 

[bomar76]

Re: How to check Thunderbolt IV module

After I posted that question I saw it was a 1990, so that answered that.<br />Make sure you get the EXACT SAME module as it controls the advance curve.<br />I bought mine from bammarine.com and even wtih next day air shipping it was less $$$ than a dealer would charge - and quicker also!

 

[RonThom]

Re: How to check Thunderbolt IV module

Replaced module and wiring harness. It did not run before, now it does and it did not quit while running.

 

[Bondo]

Re: How to check Thunderbolt IV module

It did not run before, now it does and it did not quit while running. <br />

That's Always a Really Good Thing..................................

 

[tystick]

Re: How to check Thunderbolt IV module

what part # for the ignition module for a 1990 4.3L 155 hp and approx. price? I was looking for it at bam but only saw a ignition amplifier

 

[achris]

Re: How to check Thunderbolt IV module

Ignition amplifier and ignition module is the same thing.<br /><br />Part number is : -15247A1