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todays problem... Cranks great but wont start

E

emac

Regular Contributor
Engine has been firing up fine, last ran three days ago. Last night, go to take a ride, cranks but will not fire. It almost feels like a kill switch thing but this boat isnt set up with a kill switch, or its been disabled. I disconnected the fuel line at the screen filter and its getting gas when I pump the bulb. The plugs dont look bad, put in last september. Gonna get another set anyway, never hurts to have extras, and gonna do a spark test tonight. Beyond that, any thoughts on what might make it run great one day, and not start the next? ( I mean, other than the fact that its a boat...)
 
Start with the basics..... Take a compression test. What are the psi readings for all cylinders? The spark (with all spark plugs removed) should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it.

Note that the 7/16" gap is important... don't waste your time checking spark with the spark plugs.

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark.... or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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If you have no spark, remove the black/yellow wire (kill circuit) from the ignition switch and re-test. Do you now have spark, and if so... replace the ignition switch.

Let us know what you find.
 
I have a spark tester, its a glass tube thingie, tests one wire at a time. Used it when I was fixing an old merc. Seemed to work good.
 
Those glass tube neon testers just don't do it... they would light up even if the spark was so weak it would only jump a few thousands of a inch. You need that 7/16" gap to test the spark as I suggested.
 
Ok, no spark at all, found black wire w yellow stripe, disconnected, still no spark, gonna try a new ignition switch
 
It hasn't had a lanyard since I got it, but the box where the controls are describes one, may just the little plastic bit was there and I knocked it out accidentally?
 
If the black/yellow wire is disconnected from the pack and no spark you have probs on the motor. Go to cdielectronics.com for testing procedures.
 
Cause I'm grasping at straws. It's driving me crazy, no problems just a couple days ago. The stator is not all melts as I understand to be a sign of it failing. The wire all look good going into the engine, I didn't do the compression test because what's the point with no spark, and tide was coming in so we fished from the dock. What would you recommend be the next step? Also that black wire w the yellow stripe, it also looked like a white stripe at different spots on the harness.
 
Ended up being the powerpack, keeping a printout of the trouble shooting guide from CDI in my repair manual. Thanks for the help.
 
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