No spark from coil

C

cautionneeded

Cadet
Joined
Jul 25, 2010
Messages
8
I have a 1975 140hp mercruiser. No spark from the coil. Coil checks out fine. New points, cap, rotor, plugs, wires, condenser all installed and used part of last year. Points are opening and closing. I have not checked to see if I have any power to the Coil YET.

What is the most likely culprit (s) if my coil and other at engine ignition parts are OK?
How long can I safely direct connect 12V to my coil?

Thanks
Robert
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: No spark from coil

I have not checked to see if I have any power to the Coil YET.
Click to expand...
That is what you should be doing right now.

What is the most likely culprit (s) if my coil and other at engine ignition parts are OK?
Click to expand...
What's the difference, the most likely may not be your problem.
But from my point of veiw, if you have power to the points (you need to check with a meter) then you need a set of points. They were new last year, not this year. They are probably glazed over and while they may be opening and closing, they are not making electrical contact.

How long can I safely direct connect 12V to my coil?
Click to expand...
Long enough to do your testing, then shut it back off
 
C

cautionneeded

Cadet
Joined
Jul 25, 2010
Messages
8
Re: No spark from coil

Don S said:
That is what you should be doing right now.


What's the difference, the most likely may not be your problem.
But from my point of veiw, if you have power to the points (you need to check with a meter) then you need a set of points. They were new last year, not this year. They are probably glazed over and while they may be opening and closing, they are not making electrical contact.


Long enough to do your testing, then shut it back off
Click to expand...

OK Right after work I will re-install the coil and check for power at the + side and then at the points. Power to and through the coil will indicate the problem is in the points and no power to the coil will indicate the wiring harness or ignition switch. I think I am learning something useful at 40.
Thanks
 
C

cautionneeded

Cadet
Joined
Jul 25, 2010
Messages
8
No spark to plugs mercruiser 140

No spark to plugs mercruiser 140

My 75 mercruiser 140hp is not getting spark to the plugs. I have power to the coil and to the points. I do not see any spark at the plugs. What should I check next.
 
J

jim372

Petty Officer 2nd Class
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Apr 24, 2010
Messages
145
Re: No spark to plugs mercruiser 140

Re: No spark to plugs mercruiser 140

did you check your coil with a ohm metter?
remove wires first.
between small posts shold get between 0.75 - 0.81 ohms and between post and tower should get 10,000- 11,000 ohms
 
Don S

Don S

Honorary Moderator Emeritus
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Messages
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Re: No spark to plugs mercruiser 140

Re: No spark to plugs mercruiser 140

I merged your 2 threads together. Please don't start separate threads on the same subject, just reply to your original thread with new information
 
C

cautionneeded

Cadet
Joined
Jul 25, 2010
Messages
8
Re: No spark to plugs mercruiser 140

Re: No spark to plugs mercruiser 140

jim372 said:
did you check your coil with a ohm metter?
remove wires first.
between small posts shold get between 0.75 - 0.81 ohms and between post and tower should get 10,000- 11,000 ohms
Click to expand...

The ohms check out good but I am only getting 4.5 volts at the + post. I have a very weak spark at the plugs I cannot see but I felt. Replaced points and charged battery. Tried some gas direct into the carb but no fire at all.
 
C

cautionneeded

Cadet
Joined
Jul 25, 2010
Messages
8
Re: No spark to plugs mercruiser 140

Re: No spark to plugs mercruiser 140

Update. I ran a wire direct from bat to + post of coil. The motor started fairly easy and ran well as expected for a spring start up. Now what do I do to fix the problem. Could my ignition switch be bad? I just do not know what this all means at this point.
 
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