2010 4.3L TKS Thunderbolt Ignition Troubleshooting

[tkvoice]

I have a 2010 Larson with Mercruiser 4.3L TKS (carb) that has no spark. Sometimes it does get spark when I am troubleshooting (rare 1 in 25 attempts).

I have ran down the Thunderbolt troubleshooting flow chart and I get spark on the coil with a tester and manually striking ground with the wht/grn wire that comes from the Thunderbolt module. However I have replaced the ignition sensor under the distributor cap with a brand new one and the engine won't start. It is failing at the same spot on the chart.

Any ideas where to go from here? Is it possible I got a bad ignition sensor?

Other things and history
I have checked my kill switch (that lanyard connect to) and is working as expected (ohm meter gets Open or 0 ohms when switching)
Last year lots of new parts went on including:
New Ignition Sensor
New Spark Plugs
New Cap/Rotor
New Coil

 

[dubs283]

Is it possible I got a bad ignition sensor?

Possible, not probable. Is the sensor oem or aftermarket? Is the new sensor grounded properly?

Another thing to check is the shift interrupt switch. Not often a cause of no/intermittent spark but worth checking as it does affect the ignition system

 

[tkvoice]

It's an aftermarket ignition sensor that I got off of Amazon. I don't see a name brand on it anywhere. The black wire is grounded really well.

Is there a way to check the ignition sensor itself?

 

[dubs283]

It's an aftermarket ignition sensor that I got off of Amazon......Is there a way to check the ignition sensor itself?

Ditch the aftermarket and buy oem

You've already tested the ignition sensor, old and new.

Ground should be placed on the same stud as battery cable ground, directly on top of the battery cable lug, i.e. no other ground terminals between the two

 

[nola mike]

Might also try that last test on the plug wires (or at least 1 with the rotor lined up). Your problem could be coming from the rotor/cap/plug wires as well as the sensor (which it still sounds like)

 

[tkvoice]

I found this thread "How Mercruiser Thunderbolt ignition systems work"
Lots of good information here.
I zeroed in on this comment "For troubleshooting I always remove the tacho feed wire and the white/green to the shift interrupt switch, eliminating them as a possible cause of a problem". Easy enough to crawl under dash and disconnect the Tach however my "interrupt switch" is part of the remote throttle control and is panel mounted into my fiberglass inner hull where it is near impossible to trace wires. The service manually does not do a good job to show the pin-out of the TBV Integrated Control Module so I did some searching and found this:

I cut the "White/Black" wire going to pin "E" on the large connector going to the TBV Integrated Control Module. I left a few inches so I could crimp in a disconnect connector (for future troubleshooting). Pin "E" goes to the "interrupt switch" and guess what? After cutting that wire the motor fired up. I turned it off and on a few times it does take 4-5 seconds of cranking before it starts but it is starting pretty much every try now.

I took it for a spin around the lake to charge the battery up and it ran like a champ. I didn't even notice a difference in shifting between forward/reverse with the "interrupt switch" by-passed so I probably won't even fix the "interrupt switch" and will just leave that WHT/BLK wire cut.

Thanks fubs283 for telling me about the "interrupt switch" as it was your comment that got me searching down this path.

 

[Scott06]

I found this thread "How Mercruiser Thunderbolt ignition systems work"
Lots of good information here.
I zeroed in on this comment "For troubleshooting I always remove the tacho feed wire and the white/green to the shift interrupt switch, eliminating them as a possible cause of a problem". Easy enough to crawl under dash and disconnect the Tach however my "interrupt switch" is part of the remote throttle control and is panel mounted into my fiberglass inner hull where it is near impossible to trace wires. The service manually does not do a good job to show the pin-out of the TBV Integrated Control Module so I did some searching and found this:
View attachment 380570
I cut the "White/Black" wire going to pin "E" on the large connector going to the TBV Integrated Control Module. I left a few inches so I could crimp in a disconnect connector (for future troubleshooting). Pin "E" goes to the "interrupt switch" and guess what? After cutting that wire the motor fired up. I turned it off and on a few times it does take 4-5 seconds of cranking before it starts but it is starting pretty much every try now.

I took it for a spin around the lake to charge the battery up and it ran like a champ. I didn't even notice a difference in shifting between forward/reverse with the "interrupt switch" by-passed so I probably won't even fix the "interrupt switch" and will just leave that WHT/BLK wire cut.

Thanks fubs283 for telling me about the "interrupt switch" as it was your comment that got me searching down this path.

You will likely have trouble getting out of gear especially when docking without the interrupt switch. It makes the ignition stumble when coming out of gear to unload the back cut dog clutch engagement teeth. With water putting pressure on the prop you may find that it will hang up in gear when the controller is in neutral

 

[nola mike]

I found this thread "How Mercruiser Thunderbolt ignition systems work"
Lots of good information here.
I zeroed in on this comment "For troubleshooting I always remove the tacho feed wire and the white/green to the shift interrupt switch, eliminating them as a possible cause of a problem". Easy enough to crawl under dash and disconnect the Tach however my "interrupt switch" is part of the remote throttle control and is panel mounted into my fiberglass inner hull where it is near impossible to trace wires. The service manually does not do a good job to show the pin-out of the TBV Integrated Control Module so I did some searching and found this:
View attachment 380570
I cut the "White/Black" wire going to pin "E" on the large connector going to the TBV Integrated Control Module. I left a few inches so I could crimp in a disconnect connector (for future troubleshooting). Pin "E" goes to the "interrupt switch" and guess what? After cutting that wire the motor fired up. I turned it off and on a few times it does take 4-5 seconds of cranking before it starts but it is starting pretty much every try now.

I took it for a spin around the lake to charge the battery up and it ran like a champ. I didn't even notice a difference in shifting between forward/reverse with the "interrupt switch" by-passed so I probably won't even fix the "interrupt switch" and will just leave that WHT/BLK wire cut.

Thanks fubs283 for telling me about the "interrupt switch" as it was your comment that got me searching down this path.

Glad it's working but I don't think that's your problem. If either the tach or SIS is grounded you won't get spark from the coil during the TB troubleshooting test.

 

[tkvoice]

I am not sure it is fixed either.

I measured ohms between the WHT/BLK wire (the side that is coming from the Interrupt switch) to ground and it was completely open. Absolutely no connectivity to ground. I was expecting to see this connected to ground if the interrupt switch had failed.

I went ahead and crimped in a quick disconnect on the WHT/BLK interrupt wire got it hooked back up to pin "E" on the TBV Integrated Control Module. I gave it try and it started. I turned in off/on at least 3-4 times and it started every time with the interrupt switch connected back up.

So I am not sure it is fixed either and I am not sure why everything is working again. I don't want to venture too far until I get to the bottom of this. Could it be an intermittant issue with the interrupt switch? or is it something else?

 

[nola mike]

As mentioned, if your spark test at the coil is consistently good, the failure can only be in the ignition sensor or in the cap/rotor/wires, or wiring to the sensor. If it's intermittent, then all bets off.

Edit: Also, wouldn't expect an intermittent issue with the sensor itself unless it's the wiring. Theoretically you should be able to measure a hz signal from the sensor, though I've never tried it (might also get an ac voltage depending on your dvm). May be worth measuring when it's working, and then trying again when not.

 

[tkvoice]

It's definitely not fixed.
I just got stranded out on the lake and it won't start had to get towed home. Tried disconnecting the interrupt switch and still would not start

 

[Fun Times]

Haven’t thoroughly read the whole thread, more of a glance… but if it’s basically not starting while hot?/ very hard to start, then it’s more probable of either being the TKS diode or the TKS temperature switch.

https://f01.justanswer.com/schembrinoel/daadc3ff-14e3-4932-bba3-141972ef5678_service_bullettin.pdf

 

[nola mike]

Haven’t thoroughly read the whole thread, more of a glance… but if it’s basically not starting while hot?/ very hard to start, then it’s more probable of either being the TKS diode or the TKS temperature switch.

https://f01.justanswer.com/schembrinoel/daadc3ff-14e3-4932-bba3-141972ef5678_service_bullettin.pdf

Op confirmed that he's having a spark issue. Can't think of a tks failure that would do that...

 

[tkvoice]

Here is a little video of me testitesting the ignition sensor

I guess I will buy a OEM or Sierra sensor and see if my issue goes away

 

[Scott06]

It's definitely not fixed.
I just got stranded out on the lake and it won't start had to get towed home. Tried disconnecting the interrupt switch and still would not start

Did u test for 12 v on positive side of coil when this happens ? Could be the kill switch or key intermittently dropping out

edit didnt see your last post, looks like u got a bad sensor then . Hopefully u get your money back.

 

[dubs283]

I will buy a OEM......... sensor

Oem is the only way I go with t bolt ignition sensors, anything else is a gamble. Fair witness

Same goes for alpha lower shift cables, can't recall an aftermarket one ever working properly

 

[nola mike]

Same goes for alpha lower shift cables, can't recall an aftermarket one ever working properly

The Sierra ones are good, and I've seen a couple of other decent ones. Good ones have a plastic coated inner sheath, pretty obvious if it's quality or not. Electronics, who knows, rubber who knows.

 

[tkvoice]

Fixed it
I am not really sure what the problem was but I think it might have been the TB V control module as that is the only part I did not change because it is no longer available.

I installed the EST distributor with built in control module and ditched all the TB Iignition system.
Reused the same plugs and wires. Now everything works great! Goodbye TBv

 

[nola mike]

Fixed it
I am not really sure what the problem was but I think it might have been the TB V control module as that is the only part I did not change because it is no longer available.

I installed the EST distributor with built in control module and ditched all the TB Iignition system.
Reused the same plugs and wires. Now everything works great! Goodbye TBv

Check your PM

 

[dubs283]

Check your PM

Dang, I want it too