15hp johnson only firing on 1 cylinder (help needed)

[cubmixit]

2000 15HP JOHNSON (2 STROKE) ONLY FIRING ON 1 CYLINDER, I think.
It's running rough and poor idle. I have to baby the throttle, or it dies out. Seems to run ok at high rpm's, but just not right. Runs ok on land, but poor in water.

So with motor running, I pulled one plug wire at a time. When I pulled the bottom wire, the engine kept running- replaced wire. Then I pulled the top plug wire, engine stopped running.. From what I've read, that means engine is only using 1 cyliner.

I swapped spark plugs and then I swapped plug wires. Same result on same cylinder. I then crossed the the plug wires-- top to bottom and bottom to top (at the spark plug), same result on same cylinder.

Compression in each cylinder (111 and 110). I can see spark on both plugs.

Is my coil bad? Thank you for you help!

 

[psteurer]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Could very well be a bad coil. Why don't you swap them and see if the problem follows to the bad cylinder. Also, try cleaning all the wire terminal connections while you are swapping.

 

[tashasdaddy]

Re: 15hp johnson only firing on 1 cylinder (help needed)

well it has a duplex coil, so the no spark stays at the same place on the coil, i think i would check the plug from power pack, for corrosion. if not that, replace coil.

 

[kahuner]

Re: 15hp johnson only firing on 1 cylinder (help needed)

I'm going to suggest that your problem is fuel related as in the low speed circuit. Could be the low speed circuit that is plugged, broken reed or a bad lower crankcase seal (even though your compression is fine) all of which could affect the lower cylinder only.

I'm thinking it's fuel related because you stated that the engine runs fine on the top-end (albeit that you have to feather the throttle as you increase engine speed) and the upper cylinder is doing the work at idle; evidenced by the engine dies if you pull the upper plug wire.

As you throttle up, did you see or hear any "spit-back" through the carb? If so, that would point to a broken reed. Maybe the reed is not broken buy could've been incorrectly assembled during service.

Keep us informed as to what your finding.

 

[cubmixit]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Thank you for your help....
I pulled the plug wires from plug and the coil.. They look fine to me.. No corrosion. I checked the coil to the power pack where the snap in together (5 prong)?, there is some corrosion. I cleaned as best I could and blew it out.. Started engine-- same problems....

I went back to coil... Left the connections at the coil-- Put the bottom plug wire to the top plug and then the top plug wire to the bottom plug... It wouldnt fire at all.
I replaced them back to normal.. Start on first pull.. Again- pulled the bottom wire when it was running and it kept running-- then replaced.. Pulled the top plug wire when it was running- engine died...

 

[tashasdaddy]

Re: 15hp johnson only firing on 1 cylinder (help needed)

i assume you have the spark plugs out of the motor for these test. if they were in, it would not fire over, as the spark is not in sinc with the pistons. use a spark tester to check spark

 

[cubmixit]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Thanks.. No-- I actually tested with the plugs in (was told to do that)... Guess that explains why it didnt start...

Ok-- I pull the plugs and cranked.. I can see spark in both, although the top plug has a greater spark..

Someone earlier mentioned fuel could be the problem-- said it could be a "reed". I'm not sure what a reed is... Is it in the carb?

Last weekend, I tore the carb down because it wasnt running at all. I used a carb cleaner on it.. When I put it back together-- it started on the second pull and ran absolutely great... Then-- I took it out on the water and thats when I started having the problems that I've explained.

Any other ideas? Thanks again for your help!

I did order a new coil.. Should be in sometime at the end of this week.

 

[cubmixit]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Oh yeah-- at higher rpms, there are no back fires... When you let off the throttle, it starts to bog down...

 

[kahuner]

Re: 15hp johnson only firing on 1 cylinder (help needed)

The reeds are located behind the carb, in the intake manifold, not in the carb itslef. A broken reed is now not likely because you've added that after rebuilding the carb it ran great, then failed on the water.

Don't overlook the simple stuff as you go along. First, 2 new plugs or put the bottom cylinder plug in the upper cylinder. Start the engine and see if the engine will run on the upper cylinder only with the lower cylinder plug wire off. This would eliminate a bad sparkplug.

Next, dirt in the carb (again) AFTER your rebuild. Seems funny that the engine ran well after the rebuild, then started acting up on the water. A bad coil (although I'm not ruling it out) would've been bad before AND after the carb rebuild.

The circuit that you need to concentrate on is on the top of the carb. Both the front of the carb (screw) and on the side where you can adjust the low speed idle circuit mixture (screw and spring).

Try to rule out the sparkplugs first; then get back to us.

 

[cubmixit]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Thanks very much! I can see spark in the both plugs, but dont have a tester. I'll buy some new plugs on Monday just to make sure..

Also- I have adjusted the low speed idle on the side of the carb(the one with the spring), but I dont really get any response from the engine in doing so.. I havent touched the top side screw.. Can you tell me the turns for both?

And-- I already bought a coil. It should be in at the end of the week.. Thank you!!

 

[kahuner]

Re: 15hp johnson only firing on 1 cylinder (help needed)

If you can adjust the screw on the side of the carb and it doesn't have any effect on the operation or idle quality, the low speed circuit could be your problem. The screw on the side of the carb is a low speed mixture adjustment screw. Turn it out and you richen the mixture, opposite when you turn it in. I'm going to guess that the recommended setting should be around 3/4 to 1 turn out from seated (all the way in). What is it set at now? 1/2, 3/4, how many turns out from seated?

If you can turn the screw on the side of the carb out 2 turns and there's no difference in idle quality from say 1 turn out, the low speed circuit is your problem. It's gotta be blocked. You definately should be richening the mixture to the point the engine won't idle at all if you turn the screw out to 2 turns!!

The screw on the front of the carb is not an adjustment. Should be tight. It's there to give you access to the low speed circuit orifice. If you continue to have problems (not sure if the circuit is plugged again) that's the path you should concentrate on. It's connected to the screw on the side of the carb (low speed mixture screw)

 

[cubmixit]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Thanks very much... I bought a carb kit today and will rebuild. I also bought some new plugs.. I'm waiting on the coil to get here via UPS which looks to be on Thursday or Friday...

As for the screw on the side of the carb, it's sitting at 3 full turns right now... However, when I tried to set it to the "seated" position by turning it all the way in- it never stops turning.. It goes in, but doesnt stop.. I must have messed something up with that, so hopefully the carb kit will address that issue..
The carb kit didnt come with direction, so wish me luck...

Once done, hopefully all of these changes will address the botton cylinder that isnt working...???


Again-- thanks for the help...

 

[kahuner]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Just to make sure that I'm on the right track (model yr of your engine) and that we are talking about the same screw, the pic below is a exploded view of your carb. Right?

The screw that I was referring to is item #15, located on the top plate of the carb w/ the spring. Is that the screw that keeps turning? And if you took that screw out, is it tapered like #15 in the exploded view?

The name of that part is a slow speed needle valve P/N 0339218. That part will probably NOT be in the rebuild kit.

I'm scrath'n my head now............ that screw keeps turning!

Could you let us know if we're both talking about the same screw?

 

[cubmixit]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Yep.. That's it.. The same one... There are three parts to it.. The needle, the spring and the housing that the needle fits into... The housing came loose...???

I bought a carb kit, and that needle was not in there.. I did manage to the the housing back in place, now I have the needle sitting at one full turn out of "seat"...

So my next move is to mount the carb, put new plugs in, install the new coil... Everything should be done on Thursday. Hopefully it will go good.... Thanks.. Any other ideas...

 

[bktheking]

Re: 15hp johnson only firing on 1 cylinder (help needed)

The idle needles don't come with the kits, if it's damaged in any way it should be replaced.

 

[kahuner]

Re: 15hp johnson only firing on 1 cylinder (help needed)

As I mentioned in my last post, and as bktheking has just mentioned, that needle is not in the kit. To bktheking's point, if the taper on that needle is damaged, it needs to be replaced.

Back to a comment that you made earlier, that the screw (on the side of the carb) just keeps turning. You'll need to determine if the plastic insert (that holds the idle mixture screw in place) is not stripped, or so worn it doesn't capture the threads of the screw. Maybe that's why it keeps turning. The seal between the screw and the plastic insert needs to be tight.

The plastic insert is a $2.00(?) part, easily replaced and cannot be overlooked. I still can't understand HOW that screw could just keep turning?

As Red Green always says: "Remember; I'm pullin for ya! We're all in this together!!"

 

[cubmixit]

Re: 15hp johnson only firing on 1 cylinder (help needed)

1. Just finished... Rebuilt kit on the carb.. Needle seat at 1 turn...
2. New Coil.. Just installed.
3. New Plugs.. Just installed..
= Engine started on 2nd pull and ran a little rough, then went fine. Even idled, but a little rough and needs an adjustment..

I then checked the bottom cylinder.. Started engine and pulled the top plug wire, and the engine stalled again.. Put plug wire back on and start engine... Pulled bottom plug wire, engine kept running... It seems that the bottom cylinder still isnt firing, although the engine seems to run pretty good (as compared to how it was running).

About the tapper, when rebuilding the carb, I notice the tapper was out. I put in back in and it seems to be fine... I put the needle back in the tapper and set it at 1 full turn.

Any ideas.. Is the problem the power pack? If so, how can I test that?
Thanks for your help....

 

[Johnsorude]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Their are very small feeder jets for idle fuel in the throat of the carb just at the bottom of the throttle plate. All the adjusting in the world will not help if these ports are dirty and blocked. it seems that the fact that the engine performs above idle under power shows it's getting fuel from main jets, but idle jets are different jets. Start the engine and let it idle for a few minutes. shut down. pull both of the plugs, the plugs should be damp with fuel. if the bottom is dry the idle ports are clogged and the cylinder is being starved. I've found that a good burning tip cleaner will work wonders.

 

[bktheking]

Re: 15hp johnson only firing on 1 cylinder (help needed)

First of all you need check for spark the "proper" way instead of pulling off wires. Get a spark tester and test it, you need to be able to test the distance the spark can travel and see how good the spark is. Second, post the model number of your motor, this motor could have a stator, maybe not, you need to figure out what is causing your issues by process of troubleshooting instead of process of elimination, it can get quite expensive. The last 15 to have an issue on here with spark had a frayed wire going to the powerpack, the guy repaired it for a $1.00 i'm sure and he's back on the water. Have you had the flywheel off to inspect the wiring and condition of the trigger sensor or flywheel magnets? You may also have a bad lower crank seal, my 15 had one, the guy complained that he constantly fouled the lower plug, problem found.

 

[cubmixit]

Re: 15hp johnson only firing on 1 cylinder (help needed)

Here's the engine and model: 2000 15 HP Johnson RSSM.....
Ok-- did the spark test with a spark plug "light" tester... Spark looks good to me... Both look to be producing the same sparK.


New plugs.
New Coil
Rebuilt Carb
Engine starts right up and now idles pretty good now..

Sometime sluggest when rev'ing up, but comes back down and idles ok.
Sometimes I go to wot, but engine only rev's half speed.-- then goes up to wot...

I pulled the bottom plug wire. Engine runs. Replaced wire.
I pulled the top plug wire. Engine stops running..

What else can I do?