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Author Topic:   Honda 8-HP Spark Coil
IFish4Tuna posted 06-20-2006 08:07 AM ET (US)   Profile for IFish4Tuna   Send Email to IFish4Tuna  
My 8-HP Honda four-stroke began running with a very high idle on Saturday this past weekend. On Sunday, it began to have trouble running or starting. On Monday night I tried to start it and could not.

This morning (Tuesday) I checked for a spark in each plug but did not see one.

Does this sound like the symptom of a coil problem?

Whaler_bob posted 06-20-2006 11:49 AM ET (US)     Profile for Whaler_bob    
If it is a two cylinder engine with an ignition coil for each cylinder and you do not get spark on either spark plug lead then it is probably not an ignition coil.

You have to look for a common component like the charge coil, timing sensor or power pack/ignition module itself. Most factory authorized repair shops can/will test the CD pack for you if you bring it down there.

Look for any frayed or damaged/shorted wires around and under the flywheel or near other moving parts like the throttle linkage. Check the kill switch wiring for broken or frayed insulation too.

Chuck Tribolet posted 06-21-2006 12:07 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I can't think of an electrical problem that would cause a
high idle then a no run, except maybe an erratic advance problem.

How did you check for spark in each plug?


IFish4Tuna posted 06-23-2006 07:54 AM ET (US)     Profile for IFish4Tuna  Send Email to IFish4Tuna     
Thanks guys. The way I checked for spark was by removing the plug and resting it up against the block while cranking. Not the most accurate of methods I know due to the jiggle/vibration factor, but it's worked in the past for lawnmowers, etc. I probably need one of those plug clamps.

Anyway, yes couldn't find a spark on either plug.

I just ordered the coil assembly which is due in today. It feeds both spark plugs. My service manual is due in another week, so this is a bit of trial and error until I get specifications and method of debug.

A exploded view illustration which shows the coil assembly. MANY Thanks in advance for your guidance. I'll keep you posted. Oh - and what is an erratic advance?

Chuck Tribolet posted 06-23-2006 09:43 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The point in the cycle where the spark fires varies depending
on a number of things, possibly including RPM, manifold
vaccum, throttle position, temp. Some times the mechanism
that triggers this stuff goes haywire, and the advance varies,
perhaps wildly, from where it should be.


Whaler_bob posted 06-23-2006 11:49 AM ET (US)     Profile for Whaler_bob    
Being thay your engine uses a single ignition coil for both cylinders, it's just as likely to be at fault as the other items now. The service manual would probably give you resistance values for the low and high voltage sides..
IFish4Tuna posted 06-23-2006 04:18 PM ET (US)     Profile for IFish4Tuna  Send Email to IFish4Tuna     
problem solved

I'm not entirely sure it was the coil assembly, because I didn't check for sparc afer installing it.

It did not start up immediately.

I did notice a bit of sheen on the water surface around the engine, and I notice the primer needed a few good squeezes. It was then that I realized one of the screws holding the carberator to the manifold was completely unscrewed. I have a hunch this is the actual culprit. Once I screwed it in, it cranked like the good ole' days.

Thanks again for the helpful suggestions.

I guess in retrospect I can feel comfortable w/ my new coil, and in addition, I should get a better method of checking for spark.


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