Stumped. No spark.

[findinghomer]

Guys I am stumped and I'm not getting spark and Ignition systems are my weakness. Before I took the boat out on the lake for the 1st time this year I ran it on muffs and it ran great, So I headed to the gas station filled it up with gas and dumped it into the lake. It fired right up, but stalled within 60 seconds. Usually that's no biggie when it's cold, but this time was different when I turn the key it just cranks and cranks and cranks and cranks. Thinking I flooded it I waited a while. After a while still the same thing. So I pulled it out. The next day I decided to give it another shot because it usually will fire right up if I write-up if I flooded it and it sat overnight. Dropped it back into the lake still just crank crank crank doesn't even attempt to start. So I brought it home. After bringing in home I'm realizing I'm not getting spark. I bought a new coil , it did not fix my problem. There is a red and white lead wire coming from the Ignition module that goes to the Ignition sensor that reads 11.8 V ( Everywhere else reads well over 12 V as my batteries are fully charged on a trickle charger) but drops down to 10.3 as soon as my tester puts a load on it. Does this mean Ignition module prob? Or is it likely the Ignition sensor in the distributor? And if it is the Ignition sensor in the distributor how do you get that out of there? The engine is a 1997 5.7 , 350, thunderbolt IV ( I Believe).

I think I'm headed in the right direction but these systems are complicated for me so any help would be appreciated thank you

 

[achris]

If you're getting 12v (or near enough) to the sensor, then it's more likely to be the sensor. In the stickies I have an article on the system. At the end is the troubleshooting flowchart, follow that and you'll have your answer..

Chris...

 

[findinghomer]

If you're getting 12v (or near enough) to the sensor, then it's more likely to be the sensor. In the stickies I have an article on the system. At the end is the troubleshooting flowchart, follow that and you'll have your answer..

Chris...

So I'm using a test light with voltage. And when I put the test light on it , it does read 11.8 for a second but then it immediately drops down to 10.3 I guess because of the load of the test light. Is that OK? I'm just wondering if the sensor's not getting the proper voltage to it

 

[achris]

Using a digital Multimeter. The load of the test light is too much for the module.

 

[findinghomer]

Using a digital Multimeter. The load of the test light is too much for the module.

Wow... I wouldn't have thought that , that's why I asked , thanks. So how do I get the Ignition sensor out of the distributor?

 

[Scott06]

Wow... I wouldn't have thought that , that's why I asked , thanks. So how do I get the Ignition sensor out of the distributor?

If you haven't go through the troubleshooting guide in stickies to verify it is the sensor. To replace remove cap and rotor to access the sensor

 

[findinghomer]

If you haven't go through the troubleshooting guide in stickies to verify it is the sensor. To replace remove cap and rotor to access the sensor

Yeah I see the sensor, but the rotor seems to be stuck in place ,do they seize up? Do I just need to pry it out of there?

 

[Scott06]

Yeah I see the sensor, but the rotor seems to be stuck in place ,do they seize up? Do I just need to pry it out of there?

Merc puts them on with loctite its just pushed on, so most of the time you have to destroy it to get it off… i used a chisel the last time.

 

[findinghomer]

Merc puts them on with loctite its just pushed on, so most of the time you have to destroy it to get it off… i used a chisel the last time.

I got it off thank you. The sensor contact was rusted and corroded, The inside of the button also had rust on it. I tried hitting everything with sandpaper Is to clean the surfaces, thinking I might at least figure out that that is the problem so I can order new parts. But it's still didn't work after that. I'm thinking I'll just order a new cap rotor button and Ignition sensor.

 

[Scott06]

I got it off thank you. The sensor contact was rusted and corroded, The inside of the button also had rust on it. I tried hitting everything with sandpaper Is to clean the surfaces, thinking I might at least figure out that that is the problem so I can order new parts. But it's still didn't work after that. I'm thinking I'll just order a new cap rotor button and Ignition sensor.

cant say this enough in this thread…Use the troubleshooting guide it is a functional test of the complete TB system https://forums.iboats.com/threads/how-mercruiser-thunderbolt-ignition-systems-work.676476/

the chart in there will guide you through identifying what isnt working

 

[findinghomer]

cant say this enough in this thread…Use the troubleshooting guide it is a functional test of the complete TB system https://forums.iboats.com/threads/how-mercruiser-thunderbolt-ignition-systems-work.676476/

the chart in there will guide you through identifying what isnt working

OK thanks I'm going to read through this tonight. I put a new distributor cap, rotor and Ignition sensor in , still no spark. I noticed that 50 amp red button doesn't really click like a button like it's stuck. Should that click? If I connect the 2 terminals will that bypass it? Maybe that has something to do with it *shrugs

 

[achris]

You've got 12v at the coil+, there's nothing worth with the circuit breaker.

It only clicks when pressed if it's been tripped out. If it's not tripped it won't do any clicking...

Chris...

 

[findinghomer]

cant say this enough in this thread…Use the troubleshooting guide it is a functional test of the complete TB system https://forums.iboats.com/threads/how-mercruiser-thunderbolt-ignition-systems-work.676476/

the chart in there will guide you through identifying what isnt working

It did explain ! I didn't realize that those 2 Gray wires were part of the system, somebody told me those go to the tach and the lanyard safety switch and to just remove them and see if it will start. I put those wires back on and it fires up

 

[findinghomer]

You've got 12v at the coil+, there's nothing worth with the circuit breaker.

It only clicks when pressed if it's been tripped out. If it's not tripped it won't do any clicking...

Chris...

OK thanks for the explanation. I just thought maybe the button was stuck lol. I got it figured out. You guys are awesome thanks for your help