No spark and no power at ignition coil?

[MikeDobbs]

Hi everyone. Troubleshooting a Mercruiser 3.0lx that won't start. Put an inline spark tester on this morning and saw no flash at the plug, or the main line from the coil to the distributor.

So, I pulled the first connector from the ignition coil and tested the power (purple line) with the key in the ignition, and turned to the first position (so dash gauges are all powered). In this position I read no voltage on the purple wire at the coil.

Am I correct in thinking that I should have 12v coming into the coil CONTINUOUSLY when the key is in the on position? If so, is it safe to run a jumper from the battery to the coil to see if I get a spark?

Thanks

 

[achris]

Yes.

 

[Fun Times]

So, I pulled the first connector from the ignition coil and tested the power (purple line) with the key in the ignition, and turned to the first position (so dash gauges are all powered). In this position I read no voltage on the purple wire at the coil. Am I correct in thinking that I should have 12v coming into the coil CONTINUOUSLY when the key is in the on position? If so, is it safe to run a jumper from the battery to the coil to see if I get a spark?

Hi there, yes with the key on you should have 12 volt power at the + side of the coil purple wire...And yes you could jump 12 volt power to the + side of coil for testing/to get home on if needed but on your design coil, it's a little more challenging due to the plug connectors vs the old tower type coil where it's a stud sticking out of the top.
http://www.mercruiserparts.com/Show...br=2330&bnbr=50&bdesc=EST+Ignition+Components

If you don't have 12 volt power at the coil but you have it at the ignition key/dash then you should have a break in the purple wire leaving the helm heading back to the engine.

Ensure your safety lanyard switch is in the up/run position by physically moving it a few times as depending on how the boat was rigged/wired up, that could be the first place to lose the connection on some designs. Do the gauges turn off with the lanyard switch off? Most do.

Next, check and wiggle the main wire harness 10 pin cannon plug at the engine while the key is on to see if you get your power back on at the coil.

 

[MikeDobbs]

Thanks for the responses everyone. Since the original post I studied the wiring diagram until I felt it would be safe to jump the coil, and that's what I did. FunTimes- you are correct about the connection being difficult- ended up cutting a cotter pin into two pieces and that was just the perfect size to fit in there.

With power at the coil I had a spark both at the distributor, and at each of the 4 spark plugs. However, the engine still would not start up (although for the first time it sounded like it wanted to). A couple of times one or two cylinders would "catch" but it just never strung any together to fire up.

Then, at the suggestion of someone else I checked the shift-interruptor/cut off switch (mounted atop the valve cover) and it turned out that this didn't have power either. So I'm wondering if that may have to do with the engine not firing up once I supplied power to the coil? I'm not sure how that thing works exactly, or what it would do in an unpowered state- if anyone has some insight into that I'd appreciate it.

As for the wiring harness the connections are shiny and clean- no worries there. So I guess I need to look elsewhere.

Does anyone know of a way to test whether I have power from the purple wire AT the harness? When I disconnect it there is no power, so I'm not sure how to determine if the break if between the dash and the harness connector, or between the harness and the coil/interruptor switch...

 

[Bt Doctur]

First you need to underststand how the system works. have you worked the throttle a few times to get some gas into the carb? Have you tried pouring a shot glass into the carb?
The shift interrupt circuit depends on the year and type of ignition you have. a engine serial would be very hrelpful

 

[MikeDobbs]

Bt Doctur:
Engine serial #: 0K277779

Working the throttle does not pump gas into carb- I think there is something wrong with the carb. Bought a rebuild kit and tore it apart yesterday, but all the brass tubes (are these jets?) chipped off at the slot when I tried to remove them (yes, I was using a large slotted screwdriver), so it looks as though I'll need to buy a rebuilt carb unless I try to get those things out with a screw extractor or something

 

[Eric 3.7LX Alpha 1]

Hey Mike, before you go tearing into the carb, watch these videos:

http://forums.iboats.com/forum/engi...e?s=426553ee5649f282857b928ace09bdfe&t=362542

 

[MikeDobbs]

Eric- well it's a little late for that ; )

Those videos are for a larger carb, but I did the disassembly following along with the video from Mike's Carb on the Mercarb 2BBL same as mine. Just the darn brass gave way on those jets...

I actually have a post about that- I'd love everyone's opinion on my carb dilemma: http://forums.iboats.com/forum/engi...es/9927718-how-badly-have-i-messed-up-my-carb

 

[MikeDobbs]

PURPLE WIRE UPDATE

Hey everyone, here's where I'm at. Ran wild around the boat with a continuity tester this afternoon. The purple wire is all good on the engine harness side (that is to say, I have good continuity from the purple wire in the harness to each of the 4 powered items: alt, coil, shift interr, choke).

I located a large black wire connection under the dash which seems to contain all the wires leading out from the big engine harness. I have good conductivity for all wires except the PURPLE and the grey (optional warning alarm, which I don't know if it's installed on the boat so there may not even be a wire there).

So, it seems to me the best way forward may be to just splice a new purple wire onto the harness a couple feet from the big boat/engine connector, and then run that new purple straight back to the ignition switch. Does this sound like a good fix to everyone?