Tb IV intermittent spark ?$#???

04fxdwgi25

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The main indicator here is the 12VDC to the coil +. That needs to be a constant.
If it comes and goes, there is a problem in the wiring harness before the coil.
Things to check, just name a few of the common offenders:
* Wiring / connections
* Ignition switch
* Man overboard / safety shut off switch
* Circuit breaker feeding everything
* On Alpha drives, the interrupt switch on the engine that shift cable connects to.

Doing a full tuneup is certainly a positive ie: plugs, cap, rotor and reluctor wheel. But throwing good money down the rabbit hole to just replace parts to see if it "fixes it" (known as Easter egging) is never a good idea.
 

nola mike

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Green/red to and from dizzy lose... striped post. Cleaned it, re-nutted it secure (as much as I could).
Forgot about that part. Yes new sensor, other new tune up stuff won't hurt but isn't current cause of your problems.
Like @04fxdwgi25 (and me earlier) said, consistent 12v to your coil is the most important thing to get sorted. You can try to jumper direct 12v to your coil pos and see if you get a spark then.
 

mrzooom

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Ok, I received no sensor...however, my old one has posts where grn/wht and rd/wht connect to...the new one however come with leads instead. So I don't want to wire it wrong...how exactly do I bypass the posts if they were there? Any suggestions?
 

dubs283

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If you purchased an oem sensor it has instructions and parts for proper connections

If you didn't purchase an oem sensor do yourself a favor and get one.
 

mrzooom

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I now get consistent 12.5 v's to +coil w/key on, I have to check what It gets while cranking I would assume...but no spark from coil tower to ground...
I am going to go over the breaker connections at the engine side again this morning, I am going under helm/ gage panel, and then the remote hardware and clean up all connections I can find.
Then I will report back as to what I find out today...ok
I am getting confused again but what I am thinking is as just part of the process of elimination, I want to clean up areas I know I wasn't as thorough as I should have been. Then I'll check my voltage again at coil and then while cranking, correct?
 
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04fxdwgi25

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You can connect an old school dwell meter to neg side of coil. If it shows dwell while engine is cranking, then system is working to the coil..
 

mrzooom

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Constant 12v a coil+ key on. 9 - 10v while cranking. Nothing beyond that point.

Thinking cap & rotor wheel? Wires?

If the wires in and out of alt'r also got wet like everything else, don't I need to clean up those contacts as well? I guess my problem is not dependant on such...
 

mrzooom

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Ok, finally, well, after cleaning and rewiring the alt wiring contacts,etc., and the slave/breaker station etc., I still get 12v at + coil/key in run position, but when I go to next test step I get 0v from red/wht wire coming from ignition module...so do I replace new after market sensor with OEM then retest?

I deduce such is my only logical choice at this point, correct?

Thank y'all in advance!
 

Scott06

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Ok, finally, well, after cleaning and rewiring the alt wiring contacts,etc., and the slave/breaker station etc., I still get 12v at + coil/key in run position, but when I go to next test step I get 0v from red/wht wire coming from ignition module...so do I replace new after market sensor with OEM then retest?

I deduce such is my only logical choice at this point, correct?

Thank y'all in advance!
No that means you have a bad ignition module .
 

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mrzooom

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Ok...oh ****, those are not cheap (?) And only come used as I am aware...

Any reputable sources suggested?
 

Scott06

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Ok...oh ****, those are not cheap (?) And only come used as I am aware...

Any reputable sources suggested?
Ebay has a bunch of tb4 modules listed for not terrible prices

or replace entire TB set up with a delco est
 

mrzooom

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So, since everything got soaked in the river when submerged, I am wondering if I should detach the harness and all/any wires to and from module to dizzy/coil as I haven't done such yet, dur... I'll report back...

Yeah, eBay shows a few brand new for upwards of $400 and more, but then other used ones approximately $200 range, but without warranty and none accept returns so who would spend the money on used...end up with crap that doesn't work again...
 

Scott06

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So, since everything got soaked in the river when submerged, I am wondering if I should detach the harness and all/any wires to and from module to dizzy/coil as I haven't done such yet, dur... I'll report back...

Yeah, eBay shows a few brand new for upwards of $400 and more, but then other used ones approximately $200 range, but without warranty and none accept returns so who would spend the money on used...end up with crap that doesn't work again...
I am running a used one for the last 8 years on my boat, and bought a used spare. If they list it as working you can try it out when you get it. Either way for $400 for a new one that less work and cost than a delco est

You should check the wires for corrosion and resistance since the boat was a submarine... My brothers center console had water in the conduit under the floor from engine to helm. Boat worked fine when winterized , wouldn't start next spring , had a huge amount of resistance in the cable such that no voltage was getting to the engine
 

flashback

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I am running a used one for the last 8 years on my boat, and bought a used spare. If they list it as working you can try it out when you get it. Either way for $400 for a new one that less work and cost than a delco est

You should check the wires for corrosion and resistance since the boat was a submarine... My brothers center console had water in the conduit under the floor from engine to helm. Boat worked fine when winterized , wouldn't start next spring , had a huge amount of resistance in the cable such that no voltage was getting to the engine
Your an adventurous man, I'm shy about buying used electronics.
 

Scott06

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Your an adventurous man, I'm shy about buying used electronics.
Safety is for sissies..
electronic components either work or they don’t. If its guaranteed to be functional its no issue. so many of the TB modules are NLA so not much choice.
 

mrzooom

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That's the catch all, most sellers on eBay do not offer any guarantee, warranty, nor returns....
 

mrzooom

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Now I am getting 12v at coil +, and 11.84 coming out of module via red/wht wire, followed by 8.62 at the red/wht going into the distributor...now where do I go? Still no spark coming out of coil tower?
 
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04fxdwgi25

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Did you follow the Mercruiser TSB troubleshooting I sent in post # 14?
Distributor module problem?
coil problem?
 

mrzooom

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Yes, only I have to admit that when using the gap tester from coil tower to ground, I may not be doing it correctly as such I was just using a spark tester from coil to ground.
 
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