Cyl #4 not firing

[TAC_Double]

Out on the lake today my engine developed a miss to it. When we got it back to the dock I checked the spark and found #4 not firing. I swapped the coils from 2 to 4 and it still does not fire.

What should I look at next?

1975 85hp

 

[Joe Reeves]

Re: Cyl #4 not firing

If you're saying that the original coil that did not fire still doesn't fire when you switched coils, then the coil is faulty.

 

[The-Machinist]

Re: Cyl #4 not firing

Try these tests, see where you end up.
http://www.boatpartstore.com/page31.asp

 

[TAC_Double]

Re: Cyl #4 not firing

It was late when I posted this and it was a long day. I swapped the coils from #2 to #4 to see if the problem followed the coil over to #2. It did not follow the coil. No matter what coil is on #4 it does not fire.

 

[tschamp20]

Re: Cyl #4 not firing

seems to me that the powerpack is not firing #4.

 

[iwombat]

Re: Cyl #4 not firing

Have you swapped the plug and the wire also, or just the coil. Might want to do that before shelling out for a power pack.

 

[TAC_Double]

Re: Cyl #4 not firing

I just swapped the coil. I was using a spark tester at the time.I even changed the ground a few times just to be sure. I would hate to buy a power pack if it's not cause.

 

[TAC_Double]

Re: Cyl #4 not firing

OK, I Have the boat at home now so I can work on it easier. I changed the coil for #4 with a new one that a friend had just to make sure it was not the coil. Still no spark....

I looked at the tests that someone had posted for the power pack. I am having a hard time understanding them...

Are these done with the enigne running? Or just being cranked?
What does DVA stand for?
What is a load resistor?

Can anyone explain these tests to me?

Also, Is there anything else other than the power pack that would cause just one cylinder not to fire?

I hope someone has some ideas.

Thanks!

 

[johnson1989]

Re: Cyl #4 not firing

Check for loose wires, possible breaks or pinches. Replace or move from another. My one cylinder not firing turned out to be a small non visible crack sparking over to the block or cowling cover.

 

[tashasdaddy]

Re: Cyl #4 not firing

thats the reason we say swap a coil you know that is working with the bad on. there have been new coils that are bad. usually if the problem stays with the cylinder that's not firing, it is the power pack.

 

[chbailey]

Re: Cyl #4 not firing

I'm assuming you checked the plug for fouling or swapped with another to see if it was bad? A new one is pretty cheap too. I reversed the firing chain on my 2-stroke to see if the cylider problem would follow. It didn't, so it eliminated the power pack. Not sure how easy that is to do on the 4.

 

[TAC_Double]

Re: Cyl #4 not firing

I have swapped the coil with a new one, swapped it with the one from #2 and replaced the spark plug. So I am certain it's not the coil.

Does this leave the power pack as the only other possible cause?

 

[chbailey]

Re: Cyl #4 not firing

Sounds like the power pack is all that's left.

 

[ccnstlr]

Re: Cyl #4 not firing

could be that the trigger (sensor) wire for that cylinder not doing its job. So the timer base could be the issue, not the pack. must check the resistance on the timer base to eliminate it before buying a pack.

 

[TAC_Double]

Re: Cyl #4 not firing

How do I do that?

 

[ccnstlr]

Re: Cyl #4 not firing

Try the procedure toward the bottom of the page under 4cyl Engines as mentioned in an earlier post. Specifically item #6 is what I was referring to in my earlier post.
http://www.boatpartstore.com/page30.asp

 

[TAC_Double]

Re: Cyl #4 not firing

If I did test #6 right, I got 11.6 between 1-3 and 11.7 between 2-4. I did this test with the key off, was this correct?

 

[ccnstlr]

Re: Cyl #4 not firing

seems as though that is correct and those readings are within the stated range. Looking like the pack to me, although some confirmation by one of the more seasoned vets like tashasdaddy or Joe Reeves would be good. They have taught me a ton on this site, they are a wealth of info.

 

[TAC_Double]

Re: Cyl #4 not firing

Thanks for the quick reply, and all of your help. I will hold out to hear some other thoughts before I order the new pack. Hate to waste the money if not needed.

Thanks again!

 

[TAC_Double]

Re: Cyl #4 not firing

Since it looks like I am heading towards getting a new power pack. Who makes a better pack... CDI or Sierra?

Unless someone has one laying around that will work on my engine of course