no fire in one cylinder

[dwhudson]

i have a 1976 115 johnson...there is no fire in one cylinder....could this be the ignition coil for that cylinder? The coil to that cylinder is cracked pretty bad....or could it be the power pack causing no fire to one cylinder?

 

[Darian F.]

Re: no fire in one cylinder

Well it could be either one, but before you spend the cash try this trick.<br /><br />First label your wire colors and locations on the coils and power pack.<br /><br />Next remove the "bad" coil and temporary swap it with the good coil.<br /><br />If you now have spark where the "bad coil lived"<br />you do have a bad coil<br /><br />If the powerpack is bad <br />You can put a "good" coil on the cyl with no spark and you still will have no spark.<br /><br />This should keep you busy for a while <br />good luck and keep posting,<br />Darian

 

[dwhudson]

Re: no fire in one cylinder

swap the entire coil around or only the wires in the power pack?

 

[ob]

Re: no fire in one cylinder

As long as the wires will reach,you can just swap the signal wires from powerpack to two coils and see if your "no spark" location moves.

 

[dwhudson]

Re: no fire in one cylinder

hello I'm back......<br />the cylinder is getting fire but plug does not have a burnt look like the other three.....what could this be? I think it is getting gas because plug looks wet....Have tried 4 different new plugs....have heard water could be getting in from bad head gasket is this true?

 

[ob]

Re: no fire in one cylinder

So,Are you now getting fire on all cylinders??<br /><br />If so,perform a compression reading and see if the cylinder in question is low.Does sparkplug of that cylinder look steamcleaned as in "new looking.If so,that cylinder may be getting water intrusion.

 

[dwhudson]

Re: no fire in one cylinder

yes all 4 cylinders are getting fire...and that plug does look clean....what is the next step

 

[ob]

Re: no fire in one cylinder

Compression test.

 

[dwhudson]

Re: no fire in one cylinder

if compression check is fine, does that mean there is no problem with head gasket or no water in that cylinder.......the plug does look clean...

 

[ob]

Re: no fire in one cylinder

It doesn't necessarily mean that no water is getting into the cylinder as we have not established that water is in fact getting into the cylinder.It will simply eliminate the possibility of a failed head gasket or cracked cylinder wall as a water intrusion source.The sparkplug of the cylinder in question could also look cleaner and drier as a result of it running lean due to a fouled carburetor.However ,at this point in the troubleshooting process we can't assume anything until we have eliminated all possible sources one at a time ,preferably in the order of most common or likely.

 

[Darian F.]

Re: no fire in one cylinder

You now have spark on all cylinders,<br /><br />So this baby should run, Does it?<br /><br />If not you have, fuel, timing or compression problems.<br /><br />or do you have 1 cyl not producing power <br />Not quite sure what you are asking?<br /><br />anyway glad to help<br />Darian

 

[dwhudson]

Re: no fire in one cylinder

hello....I've been doing some searches through other posts on the site and I have a question about doing a compression check.....Does the motor need to be warmed up? If so, how long should it idle before checking? Also, can the carbs starve just one cylinder of fuel causing it not to fire?

 

[Darian F.]

Re: no fire in one cylinder

I always do a compression test with engine cold.<br />You can't burn yourself that way.<br /> <br />each cylinder usaually has its own carb<br />if that is the case on your engine<br />then you can have one carb causing trouble<br /><br />remember to disconnect spark while testing compression test

 

[dwhudson]

Re: no fire in one cylinder

thanks....I have a 1976 115 johnson...it only has two carbs on it....so could it starve only one cylinder?

 

[Solittle]

Re: no fire in one cylinder

http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000001

 

[dwhudson]

Re: no fire in one cylinder

thanks for the link SoLittle......unfortunately not much help for me......The motor will start and idle fine just wont open up on the water.....also have one plug that doesn't seem to be burning....getting good spark to the cylinder though and the plug has a clean look compared to the other three not sure about "steamcleaned" looking......was just wondering if carb could starve one cylinder causing my problem......I'm going to do a compression check next....

 

[dwhudson]

Re: no fire in one cylinder

ok, I did compression check today and all 4 cylinders have good compression....all 4 have the same compression....what is the next step?

 

[ob]

Re: no fire in one cylinder

Next ,I would perform a spark test on all and particularly the suspect cylinder and insure that the sparkplug lead will jump a 7/16" - 1/2" gap with a crisp blue spark.This test is performed at starter cranking speed with a fully charged battery.<br /><br />If this test checks out well,your problem is almost surely fuel related.<br /><br />BTW,What were those compression numbers?

 

[AlBarrs1]

Re: no fire in one cylinder

You said,"...The motor will start and idle fine just won't open up on the water..."<br /><br />Check your fuel pump. You may be getting enough fuel to idle or run at low rpm, but not sufficient fuel to run at high rpm. good luck Al

 

[Solittle]

Re: no fire in one cylinder

If you have spark the quickest way to verify that it is a fuel problem is to take the cover off of the front of the carbs. Then fill a spray bottle with premix, spray some into the carbs and try to start. If it fires that confirms that the problem is fuel related - - crud in the carbs etc.