One cylinder running strong, second one not so much

[dangelor]

Hello.

I have aquired a 1985 Johnson 9.9 in pretty good shape with one issue. It was submerged in water for a bit (not sure how long).

I quickly took all the neccessary steps to resurect it and it runs (not great but runs)

I am noticing this..

While running at start speed, I pull top plug wire, motor dies quickly.
While running at start speed I pull bottom plug wire and motor stays running with a tiny difference. Obviously something is happening in bottocylinder.

Swapped plugs, no difference
Swapped ignition coils no difference
swapped plug wires, no difference.

I do know it's partially running on the bottom cylinder because at high RPM I can keep it running even after I pull the top plug wire out

I have rebuilt the carb so I'm pretty sure it's not fuel delivery, the compression in the cylinders seems to be fine (i didn't test them as I do not have the guages to do any diagnostics)

The only thing I haven't done is taken off the flywheel to inspect anything.

I thought I'd send a message this way to you folks before i did that as this might be a common thing that can steer me in the right direction.

Thanks

 

[scipper77]

Re: One cylinder running strong, second one not so much

You really should check compression, and check spark with a gap tester.

These are simple checks with the proper tools.

The long view is that you need spark, compression, timing, and of course fuel.

If you confirm even compression and a spark that jumps around 1/4" gap then and only then is it worth chasing down other issues (IMHO)

 

[scipper77]

Re: One cylinder running strong, second one not so much

If it is a rope start you could pull the rope slowly and pay attention to how the 2 compression strokes feel. If one offers noticeably more resistance than the other you likely have a compression issue.

 

[gozierdt]

Re: One cylinder running strong, second one not so much

I agree with the compression check as the first step. If the lower cylinder is damaged to where it has significantly
lower compression, it could cause the symptoms you are seeing. If the compression checks OK, then you can
start looking other places, as scipper77 suggests.

 

[Chinewalker]

Re: One cylinder running strong, second one not so much

If the motor went under while running it may have a blown head gasket...

 

[scipper77]

Re: One cylinder running strong, second one not so much

If the motor went under while running it may have a blown head gasket...

Or stuck rings. I just didn't want to speculate unroll we know that compression is bad.

A head gasket is a best case scenario here.

 

[james__12345]

Re: One cylinder running strong, second one not so much

I have rebuilt the carb so I'm pretty sure it's not fuel delivery, the compression in the cylinders seems to be fine (i didn't test them as I do not have the guages to do any diagnostics)

A compression gauge is only around 30 bucks, and a spark tester is around 6. They're both well worth the price. Its hard to know where to start when figuring out whats wrong, when you don't know if you have good compression and good spark.

 

[dangelor]

Re: One cylinder running strong, second one not so much

Thanks for all replies, much appreciated.

I have obtained both a compression guage and gap tester with the following results:
Top cylinder (good one) is 102 PSI
Bottom cylinder is 98 PSI
Sparked jumped gap on guage same on both cylinders. I'm not sure if it's far enough as the guage has units I'm not familiar with. I will attach pics to this thread.

In reading some other posts related to this topic I'm seeing a usual suspect of the CDI unit or Power Pack so called.

Does this sound like this may be the culprit in my situation?

Just a side note, after testing the spark gaps on this engine I decided to give my 63 Lightwin a try and noticed that the spark jumped further in my lightwin and cracked and was much thicker and bigger of a spark.

Any thoughts?

Thanks

 

[gozierdt]

Re: One cylinder running strong, second one not so much

Those are excellent compression numbers, so that's one problem you don't have.

Sounds to me like the powerpack may be the problem. Here's a sheet from CDI that shows
how to troubleshoot the powerpack.

http://www.outboardignition.com/support/113-2285.pdf

 

[bonzoscott]

Re: One cylinder running strong, second one not so much

View attachment 194286Thanks for all replies, much appreciated.

I have obtained both a compression guage and gap tester with the following results:
Top cylinder (good one) is 102 PSI
Bottom cylinder is 98 PSI
Sparked jumped gap on guage same on both cylinders. I'm not sure if it's far enough as the guage has units I'm not familiar with. I will attach pics to this thread.

In reading some other posts related to this topic I'm seeing a usual suspect of the CDI unit or Power Pack so called.

Does this sound like this may be the culprit in my situation?

Just a side note, after testing the spark gaps on this engine I decided to give my 63 Lightwin a try and noticed that the spark jumped further in my lightwin and cracked and was much thicker and bigger of a spark.

Any thoughts?

Thanks

Interesting about your spark. All of my points motors, everything from GM I/O to '73 rototiller sparks a flash of blue lightening. But my motors with CDI (motor bike - 15hp Johnson) flash a thin white, sometimes orange line of spark. But they seem run well and I figure it's in the power pack for some reason. Wish someone with better knowledge would clarify.

 

[scipper77]

Re: One cylinder running strong, second one not so much

I have a feeling you will not get as much help simply because you don't have a points style ignition. At least that is what is holding me up from really being able to chime in with something usefull. I will say that if you have compression you are well ahead of the game. I think I have read somewhere that a broken reed can give a no fire condition with good spark and compression. Really at this point I am posting to give you a free bump because I feel like with compression and spark you couldnt be too far from having a running motor. I know there are plenty of people here who can help you its just a matter of getting them to respond here.