No spark plug spark... 170 MC , 1985 Sea Ray

[Scott Danforth]

Make sure your batteries are charged

 

[nola mike]

Might be worthwhile to try disconnecting the coil (-) wires. Put a jumper on coil (-) and with the ignition on, touch the jumper repeatedly to ground. You should get a spark from the coil tower whenever you remove the jumper from ground. That will take the points out of the equation for now. Will let you know if your wiring to the coil as well as coil itself are capable of giving a good spark. I'd want to visualize the spark by whatever method rather than relying on the timing light. Sounds less like a cap/rotor issue at this point.

 

[glennj3]

Oops I responded before I saw your responses.. I replaced the 12 V coil just to see, no change.
So I’ve replaced everything, removed the cap. Tested my spark from the coil plug wire to the inside of the distributor with a positive spark by shorting the points. Using a spark plug tester light.
My rotor is new and is good. My distributor cap is new.
How close does the rotor come to actually touching the cap plug terminals inside of the cap? It does not look close to me. But that is the way they are. I wish I could see inside while it turns!
My battery is on a trickle charge and turns the engine over good.

 

[Scott06]

Don’t buy another coil you‘ve tried two, or at least ohm out the primary and secondary sides to verify if it is bad, google it you’ll find some ohm specs

after reading through the only things left are the condenser and setting the points with a dwell meter . Willing to betif you are getting intermittent spark this is a likely cause

 

[glennj3]

That intermittent spark was the timing light on the coil wire, not a spark.
I got a good regular spark from the coil wire by shorting out at the points. Not by turning the engine over. I ran a spark plug wire strait to the coil and got a spark also so the wires are good. I should start checking the coil wire with the engine turning over instead of shorting the points??
So far each time that I crank the engine I’ve gotten no with flash from my light.

 

[glennj3]

I just checked by cranking the engine. It does the same as shorting the points.
That should rule out everything but the condenser?

 

[Scott Danforth]

Condenser is fine if its still wired and you get spark by grounding the point wire. Willing to bet both your other coils are fine

 

[Scott06]

I got a good regular spark from the coil wire by shorting out at the points. Not by turning the engine over.

this tells you your points aren’t properly adjusted or working. When you manually short them out like this you are doing what should happen when the rubbing block opens the points then they close. Likely you have measured the open gap, but they are not closing fully Which shorts to ground and discharges the coil to the distributo.

I ran a spark plug wire strait to the coil and got a spark also so the wires are good. I should start checking the coil wire with the engine turning over instead of shorting the points??

yes get a dwell meter And check dwell while cranking.

So far each time that I crank the engine I’ve gotten no with flash from my light.

Because if the points aren’t adjusted properly (electrically opening and closing) it won’t build up energy in the coil and discharge it properly which is what I think u have going on here . Check out this video. look at the gap it jumps at the end

if shorting the points gets you a consistent spark your coil and condenser is fine i would think.
this is a really great tool to have so you can see the color (blue) and strength (gap jumped) of the spark

Lisle Coil-On Plug Spark Tester LIS20700 - The Home Depot

Transform your car into a mini office using this Lisle CoilOn Plug Spark Tester.

www.homedepot.com

 

[nola mike]

That intermittent spark was the timing light on the coil wire, not a spark.
I got a good regular spark from the coil wire by shorting out at the points.

This makes me think the problem is the points, or adjustment of the points.

EDIT: hadn't read @Scott06 response. Agreed.

 

[Scott Danforth]

Hhmmmm.....dwell meter.....

 

[glennj3]

Excellent information. I know I need to get a dwell meter. I used to have one but my cap had a door lift and I could adjust with an Allen wrench. The only way to adjust this one is to loosen the screw and move it with a screw driver (as you know). The cap has to be off so the engine can’t be running to set the dwell.
I set them with a feeler gauge at 23, they do close. I have probably caused some confusion since some things did change.
Remember it was running good but was parked for 3 months, nothing changed. I went to crank her up when I realized the plugs did not fire.
Tonight I went out to crank the engine over to make sure the coil was sending power down the wire to the cap. It does. So it appears that the spark does not pass through the rotor to the cap’s wires...

 

[Scott06]

Hhmmmm.....dwell meter.....

Be Nice

 

[Scott Danforth]

Excellent information. I know I need to get a dwell meter. I used to have one but my cap had a door lift and I could adjust with an Allen wrench. The only way to adjust this one is to loosen the screw and move it with a screw driver (as you know). The cap has to be off so the engine can’t be running to set the dwell.
I set them with a feeler gauge at 23, they do close. I have probably caused some confusion since some things did change.
Remember it was running good but was parked for 3 months, nothing changed. I went to crank her up when I realized the plugs did not fire.
Tonight I went out to crank the engine over to make sure the coil was sending power down the wire to the cap. It does. So it appears that the spark does not pass through the rotor to the cap’s wires...

the cap with the door is not marine, its automotive

you can still use the dwell meter to dial in the points without the cap and rotor installed. simply because the dwell meter goes across the coil and you can do that while cranking.

 

[glennj3]

the cap with the door is not marine, its automotive

you can still use the dwell meter to dial in the points without the cap and rotor installed. simply because the dwell meter goes across the coil and you can do that while cranking.

Yes I used a dwell on an old MGB I think it was.
Sort of difficult to crank and be inside of the engine compartment simultaneously.
Irregardless, the points close & open at 023 so a dwell is not going to change that (it should crank & fire as is).

 

[Scott Danforth]

use a remote start button with the key in the on position.

you can be right there next to the motor, press the remote start button, see the dwell meter and read it, adjust as needed. in/out and done in under 5 minutes.

 

[glennj3]

use a remote start button with the key in the on position.

you can be right there next to the motor, press the remote start button, see the dwell meter and read it, adjust as needed. in/out and done in under 5 minutes.

So funny, I called several auto parts stores today. They not only didn’t have a Dwell, they reacted like they didn’t know what one is!
I don’t believe using a dwell is going to close the points any more than they do know, so I still have to do something to move the current from the cap / rotor to the plug wires.
I’ll do another new cap & rotor. Talk to my mechanic while there.

 

[Scott Danforth]

have you called Napa?

you need to vet your auto parts store. if you walk to the counter and ask, "I need valve cover gaskets for an SBC", and they reply with "year, make, model" walk out. if they reply with perimeter or center, then they are knowledgeable enough to buy parts from.

guarantee that folks at autozone, advanced, etc. wouldnt know what a dwell meter is. they also dont know anything without looking it up.

 

[Scott06]

Yes I used a dwell on an old MGB I think it was.
Sort of difficult to crank and be inside of the engine compartment simultaneously.
Irregardless, the points close & open at 023 so a dwell is not going to change that (it should crank & fire as is).

Dwell is a measurement of the amount of time (expressed in degrees of shaft rotation) the points are oclosed, which is what builds energy in the coil, that discharges when they open. While using a feeler gauge will get you in the ballpark it is subjective because you have to have the points on the crown of the points cam and a feeler gauge is somewhat user dependent, so dwell is much more accurate.
if you take the coil wire off the distributor and ground it like in the video, turn the engine over and get a spark your points are fine and can look to the cap and rotor wires etc.

like Scott said you can jump the slave solenoid or use a bump starter switch to do this from the engine compartment.
you may have to buy a dwell meter on line as points left most cars 30 years ago. I would bet they have a modern electronic timing light that includes this feature but don’t know it...find an older gear head in the neighborhood and borrow his bet its been on the shelf for years...

 

[Scott Danforth]

without proper dwell time, the magnetic field can not build properly, therefor the energy is not there when the points open and the quality of spark suffers.

some high end multi meters can do dwell functionality using the % duty cycle function, however you have to do math.

 

[isaacs]

Does this boat use a 6V coil and ballast resistor? It sounds like it might be low voltage at the coil when cranking. Try running a jumper wire from the plus side of the coil directly to the battery and see what happens.