Evinrude 120 hp loses cylinders and dies...why?

[rustyscrew]

This is a longshot maybe. But wondering if hearing the engine will help. It starts up fine. Fires on all cylinders usually, (not in the video though), then coughs, gets out of rhythm, then loses cylinders and slowly dies. Starts right back up and does this over and over.

its a 1994 evinrude 120 hp. I am stumped. checked lots of things...corrosion, compression, spark, all good.

does this sound like a fuel or electrical problem? Timing?

see the video: http://www.youtube.com/watch?v=84nwj4w26pk

engine is started at 28 seconds. I am not throttling it. It is at idle and barely hanging on. Often it starts with all cylinders...then loses them. In the video it doesn't start with all cylinders.

any thoughts??

 

[jonesg]

Re: Evinrude 120 hp loses cylinders and dies...why?

A timing light will tell you if its losing spark.
If spark will jump 3/8th gap ( not a sparkplug gap) on all cyl's ,
then I'd rebuild the carbs.
Sounded like it was firing on 2 cylinders.

 

[rustyscrew]

Re: Evinrude 120 hp loses cylinders and dies...why?

I will check the timing today but I do know that it can jump 3/8th gap on all cylinders with the starter cranking. I checked that. Not sure if that might change on advance though....


Yes it sounds like 2 cylinders to me also. Only the 2 bottom plugs (its a V setup) are hot. I just did the carbs...maybe I screwed them up.

Is it possible that it is the fuel pump? without enough pressure only the 2 bottom carbs are filling up?

thanks

 

[jonesg]

Re: Evinrude 120 hp loses cylinders and dies...why?

I didn't mean to check the timing, just to see if its dropping spark when its running rough, that would make me look closely at the coils.
If its sparking on all cyls then I'd try choking the carbs with 2 fingers in each throat, one at a time to see if one of them isn't drawing fuel, or spray fuel into the throat, you're looking to see if rpm picks up.
Its easy to make a mistake rebuilding carbs.

 

[rustyscrew]

Re: Evinrude 120 hp loses cylinders and dies...why?

great. I checked the spark and it looks good for all cylinders.

I tried choking the cylinders with my fingers and that didn't seem to affect it much.

However, spraying fuel in the carburators worked. Making it seem that fuel is not getting to the cylinders. This is what the plugs indicated. The two top plugs were pretty dry and the bottom plugs were wet.

I am wondering if this might implicate the fuel pump if it doesn't have enough pressure to fill the top carbs? Although there was fuel dripping out of the all carbs....

otherwise it would seem to be something in the carbs. I didn't clean the jets besides blowing compressed air in the holes or measure the float drop (although eyeballed it). maybe that.....

thanks for the previous advice. I am relieved to know that the problem is carbs and fwd. meaning that I can fix this one eventually!

thanks

 

[jonesg]

Re: Evinrude 120 hp loses cylinders and dies...why?

"I tried choking the cylinders with my fingers and that didn't seem to affect it much.

However, spraying fuel in the carburators worked. "

Yeh ...dirty carbs, its not a bad idea to run a small wire through the jets.
Change the filter, draw some fuel from the tank and examine for junk.
Misadjusted floats in carb bowls, stuck float jet etc.

 

[ezeke]

Re: Evinrude 120 hp loses cylinders and dies...why?

Sounds like it's cutting out right after QuikStart disengages. You either have set the timing without disengaging QuikStart, or the idle is set too low.