2006 4.3L Mercruiser no start

[stubbsboogie]

Hey guys, for the first time ever I was towed in this weekend
2006 Mercruiser 4.3L TKS, carbed, alpha one Gen 2.
Boat has been dealer maintatined since new, done by the Merc Book.
Here we go with the issue...
Launched on Friday afternoon. Drove about 15 minutes from ramp to our river place then unloaded gear hopped back on boat to go to the local sandbar. parked and hung out for a couple hours. Started to head home, ran a bit rough on start up but then tached up ok. Within 1minute of running she just shut down. Got it restarted and looked in the engine compartment, there was an arc of electricity from the coil wire to the negative terminal on the coil. Then motor died again. Will crank over and over but not fire.
Saturday morning got my father in law and brother in law who are both certified mechanics over to look at it.

Diagnostics done...
Checked and redid all grounds. Checked distributer and wires. All good. Thought might have a defective safety switch, we bypassed that still no start. They had multi-meters and were checking things I am not sure about. Both of them seem to think it is the coil. I am going to get a coil since they are relatively cheap and try that.
past the coil what else do we try to look at if it does not work?
Thanks so much for the help guys!

 

[Silvertip]

Re: 2006 4.3L Mercruiser no start

If you saw arcing on the coil why all the testing? It is not supposed to do that but if the top of the coil is wet, oil soaked, coated with crud, that creates a nice low resistance path for the spark and consequently a "no-start" condition. Typical "no-spark" problem that should have been relatively easy to diagnose for a "certified mechanic".

 

[stubbsboogie]

Re: 2006 4.3L Mercruiser no start

All the testing was to determine if that was the issue, which everyone seemed to be agreeing it was the coil. However since the boat is in such good condition it just seemed odd to them that it would go out like that, and we did not discover the arcing until later in the diagnosing process. Mainly I was asking just to see if there was anything we missed that should be checked, since both are auto and not marine. Thanks for the help.

 

[Don S]

Re: 2006 4.3L Mercruiser no start

A faulty spark plug or plug wire will also cause the coil tower to arc. The arching can also crack the coil tower.

 

[stubbsboogie]

Re: 2006 4.3L Mercruiser no start

I have a coil on the way supposed to be here by 330 today. Hopefully I will put it on and everything will be fine. I will keep everyone posted.
Don, The plugs, plug wires and distributor were all changed at the yearly service. We did not pull the plugs, It was mentioned and talked about but did not try them.

 

[Don S]

Re: 2006 4.3L Mercruiser no start

If a plug is not firing and just dead ending the spark in that plug wire, it will damage a new coil.
When you get the new coil installed. Run the engine at idle, on muffs and remove each plug wire 1 by 1 and make sure the sound of the engine changes as the plug wire is pulled. This will tell you if that cylinder is firing or not.

Just changing the coil is like changing a blown fuse. You didn't find the problem that caused the blown fuse, and it will blow again.

 

[stubbsboogie]

Re: 2006 4.3L Mercruiser no start

Thanks a lot Don for explaining that to me I never thought of it that way. I will try that when the coil comes in today. 1 question though... Pull the plug wires off of the spark plugs themselves or off of the distributor cap? Won't I get shocked? That maybe a dumb question but I am learning...sorry

 

[Don S]

Re: 2006 4.3L Mercruiser no start

Remove them from the cap.
Before you start the engine, remove them one by one and push the boot up the wire out of the way. Then they will be easier to pull out of the cap when the engine is running. Just keep your fingers back away from the end of the wire, once out of the cap, it' can't bite you.
Since they are fairly new, they should have good insulation on them.

 

[stubbsboogie]

Re: 2006 4.3L Mercruiser no start

Thanks Don! I will let you know how it goes.

 

[spdracr39]

Re: 2006 4.3L Mercruiser no start

It doesn't hurt that bad

 

[blay127]

Re: 2006 4.3L Mercruiser no start

this is nuts! the EXACT same thing happened to me this weekend and I too had to be towed back to the marina. I came on iboats today to research what all i needed to check along with replacing the coil. Thanks for the good info everyone!

 

[ricohman]

Re: 2006 4.3L Mercruiser no start

Don is right on about a plug failure and damaging the new coil. I've replaced many COPs when the plug died and took out an $80 COP.
The arc you observed is not normal. Time for all new wires/coil/plugs.

 

[stubbsboogie]

Re: 2006 4.3L Mercruiser no start

OK I am ready to declare victory on this issue I hope! Installed new coil this evening. Started up fired on the first try. No arcing on the coil whatsoever. Sounds great just like it should. Allowed it to warm up to operating temp. Gave it some rpms to see how it would behave...perfect!
Don S I pulled each individual plug from the cap engine sound changed with each one. That is what it is supposed to do right?
Unless there is something else that I am not thinking of I think we got this one done. Thanks guys!

 

[Don S]

Re: 2006 4.3L Mercruiser no start

Glad it works for you, Just for my information, please tell me you aren't using Champion spark plugs.

 

[stubbsboogie]

Re: 2006 4.3L Mercruiser no start

I don't think so... I did not look at them. My dealer installed them. I will try to check tomorrow.

 

[blay127]

Re: 2006 4.3L Mercruiser no start

i dont doubt yall are right, but i'm just curious. How does having a dead plug affect the coil? You say the spark is dead ended, but how is that different than when the rotor is in between contacts inside the dist. cap? Isnt the spark continuously interupted? Or is the rotor grounded so that when its between contacts it still completes a loop? Again just curious of whats going on, thanks!

 

[Don S]

Re: 2006 4.3L Mercruiser no start

Spark doesn't fire until the rotor is lined up with the cap. If the spark can't find ground through the normal source (the spark plug) it goes looking for another place to find it, and that is typically one of the small terminals on the coil.

 

[blay127]

Re: 2006 4.3L Mercruiser no start

exactly, but where is the ground when the rotor is between contacts inside the cap?

 

[Don S]

Re: 2006 4.3L Mercruiser no start

Spark isn't happening then, so there is nothing to stop.

Have a look at this. http://forums.iboats.com/showthread.php?t=329742&p=2186518#post2186518

Instead of hijacking this thread with your question, you should start a new thread of your own.


EDIT: This one is even better. http://auto.howstuffworks.com/ignition-system.htm