mercruiser 120 no spark

[weightset]

so i finally got my engine to start rolling over real nice and noticed that i have no spark at all not even a little one the oints seamed to be really clean, is there anyway to test the coil, cap and plug wires with a voltmeter before i start just throwing parts at it

 

[dubs283]

Re: mercruiser 120 no spark

see here:

http://forums.iboats.com/showthread.php?t=335407

 

[weightset]

Re: mercruiser 120 no spark

does anyone know what the ohms or resistance should be when i test my coil im going to go test it in just a few mins im going to test the resistance from the positive and negative terminals and the negative and the part where it runs a wire to the ditributor

 

[dubs283]

Re: mercruiser 120 no spark

does anyone know what the ohms or resistance should be when i test my coil

have you consulted the proper oem manual for sepecific engine and ignition system??

basically you should have continutiy between all the posts on the coil

rarely is a faulty coil the cause of no spark on a conventional ignition

did you fully read and perform the steps in the how to guide i posted earlier?? - it does outline the proper way to troubleshoot a points ignition system

 

[Bondo]

Re: mercruiser 120 no spark

so i finally got my engine to start rolling over real nice and noticed that i have no spark at all not even a little one the oints seamed to be really clean, is there anyway to test the coil, cap and plug wires with a voltmeter before i start just throwing parts at it

Ayuh,.... Start with replacin' the Points....

File 'em clean for Testin',.... then replace 'em....

 

[weightset]

Re: mercruiser 120 no spark

well i went and tested them between the + and - i was gettting 0.0-0.01 and from the - to top of coil that leads to plugs i was getting 11.05-11.07

 

[thumpar]

Re: mercruiser 120 no spark

Test the voltage at the coil. You should get about 7-9v with key on and 12v while cranking.

 

[Don S]

Re: mercruiser 120 no spark

99% of the time the problem is glazed over points. But as typical, newbies to points ignition always concentrate on the coil. Usually it gets replaced and they still have no spark. Then they come looking for reasons.

Points and condenser are a basic tuneup part and should be changed yearly.

 

[weightset]

Re: mercruiser 120 no spark

well just went and tested it again with the key on im only getting 3.25-3.27v and when cranking only getting 4.4ish so not sure whats goin on with that low of a reading and when cranking with the neg terminal and the middle wire it was only getting to like 18v

 

[KC DREW]

Re: mercruiser 120 no spark

Do you have a Circut breaker button on the engine? Mine has a red button you push to reset. Just recently I could not figure out why I wasnt getting any power to anything and that was it. Mine was on the starboard side near the rear of the engine. Red button. Push it and give it a try

 

[dubs283]

Re: mercruiser 120 no spark

well just went and tested it again with the key on im only getting 3.25-3.27v and when cranking only getting 4.4ish so not sure whats goin on with that low of a reading and when cranking with the neg terminal and the middle wire it was only getting to like 18v

sounds like you found an issue, time to figure out why the voltage is low on the primary side of the coil, hint (coil gets its voltage from the wiring harness on the engine, the coil is not your problem), i will direct you back to post #2 in this thread, i did not lie anywhere in that tutorial, you WILL solve the problem if you follow ALL the directions in it!!!!!

also, unless you want to replace your voltmeter, you should not take a voltage reading at the coil tower, under normal running conditions your looking at 40,000-60,000 volts and your meter will be ruined

 

[Don S]

Re: mercruiser 120 no spark

well just went and tested it again with the key on im only getting 3.25-3.27v and when cranking only getting 4.4ish

HOW are you testing voltage to your coil? If you went from + to - terminals on the coil with your meter leads, that was a non test.

Ground the black lead of your meter on the battery negative terminal or a good clean engine ground. The red lead from your meter to the + terminal on the coil.

 

[weightset]

Re: mercruiser 120 no spark

well guess i did it wrong then lol il try again tomorrow]

 

[Don S]

Re: mercruiser 120 no spark

Kind of figured that's what happened when I read your voltages.

 

[weightset]

Re: mercruiser 120 no spark

do those voltages sound right for doing it that way lol

 

[Don S]

Re: mercruiser 120 no spark

It's a meaningless number. Test it right.

 

[weightset]

Re: mercruiser 120 no spark

Ok just tested again the right way 4.2v with key on and 10.9 when cranking

 

[Don S]

Re: mercruiser 120 no spark

The 4.2 tells me you have a loose or corroded connection between the switch and the coil. The fact that you are getting 10.9 while cranking tells me your battery is up and good cranking voltage to the coil coming from the starter.
If you put your test meter leads black to ground as before and the red positive test lead on the - terminal of the coil, you will find you have voltage there too. Check to find out, if you have voltage, put in some points as mentioned earlier, and find your wiring problem.

 

[weightset]

Re: mercruiser 120 no spark

yes i had voltage to that as well what do you mean put in some points to find out wiring issue

 

[Don S]

Re: mercruiser 120 no spark

Put in some points.

Find out why you only have 4.2V on the + terminal of the coil with the key in the run position as I mentioned earlier.