No spark

[Robbie75]

Hi guys need some help, I have a mercruiser 5.7 v8 350 with the thunderbolt ignition.
Had to completely rebuild the engine as it was out of the boat. It is now built and I am trying to get it started.
No spark at the plugs, the neutral cut out switch is in an open circuit but when I put the ignition module ground on the safety switch closes. It also does it when I ground the dizzy.
Any ideas would be greatly appreciated.

 

[Bt Doctur]

but when I put the ignition module ground on the safety switch closes.
?????????????????????????????????????

 

[Robbie75]

The black wire from the ignition module when I put it to ground it closes the circuit on the neutral safety switch

 

[Bt Doctur]

The thunderbolt has 5 leads. black ground, purple and grey to coil, White/W red stripe and White/W green stripe to dist. These have nothing to do with the neutral safety switch that is in the control box to prevent starting in gear.

 

[Bt Doctur]

can you explain what is happening when trying to start the motor

 

[kenny nunez]

I wonder if he is confusing the shift interrupter with the neutral switch in the control box.

 

[Robbie75]

Hi I have everything connected correctly white red, white green between the dizzy and ignition module. Also the white green from the safety switch am I correct in saying the safety switch is a normally open contact then when closed grounds the ignition module which prevents sparking.
When I Bell across the safety switch it is open circuit but as soon as I ground the black core from the dizzy or the black core from the ignition module the safety switch becomes a closed circuit there for the ground travelling down the white green from somewhere else. This is what I am guessing, everything turns over fine just no spark

 

[Robbie75]

I wonder if he is confusing the shift interrupter with the neutral switch in the control box.

It's the switch on the riser with the selectors

 

[nola mike]

Hi I have everything connected correctly white red, white green between the dizzy and ignition module. Also the white green from the safety switch am I correct in saying the safety switch is a normally open contact then when closed grounds the ignition module which prevents sparking.

Yes, but it isn't a safety switch. It's the shift interrupt switch, which normally grounds out the ignition for a moment to allow you to shift gears. There's a good TB troubleshooting article in the adults only sticky at the top of the forum page.

 

[Bondo]

Yes, but it isn't a safety switch. It's the shift interrupt switch, which normally grounds out the ignition for a moment to allow you to shift gears. There's a good TB troubleshooting article in the adults only sticky at the top of the forum page.

Ayuh,..... Or in the link in my signature,....

 

[nola mike]

Ayuh,..... Or in the link in my signature,....

Huh. Just realized I can't see sigs on a phone with the new software unless it's in landscape

 

[achris]

... There's a good TB troubleshooting article in the adults only sticky at the top of the forum page.

This one?

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

Chris......

 

[nola mike]

This one?

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

Chris......

No, no, I think I remember a good one at some point

 

[achris]

No, no, I think I remember a good one at some point

Oh, that smarts...

 

[Robbie75]

Excellent guys thank you for the help the trouble shooting has sorted it.