Johnson 48 spl running on 1 cylinder

[wook]

I have a 96 Johnson 48 and it is only running on 1 cylinder, the bottom one. it is getting plenty of fire and compression. Carbeurator looks clean and i pumped up the ball while running. If the fuel pump is bad would that cause it to get gas to only one cylinder and if not what could it be?

 

[Xcusme]

Re: Johnson 48 spl running on 1 cylinder

Wook, Welcome to iboats.

You mention only the cylinder that's firing. What is the dead cylinders compresson? Do you have spark to the dead cylinder? Since you have one fuel pump, it supplies fuel the each of the carbs at the same time. Since one carb has to it, the other will too. But that is where the commonality in fuel ends. Both carbs floats have to work and be clean and properly adjusted to deliver fuel mix to their respective intake manifolds. If the dead cylinder has no spark, address that issue first before looking at the carbs and the possibility of a fuel delivery problem.

Edit: Just reread your post, you weren't too clear if both cylinders had good spark and compression. If both are good, then remove and clean/rebuild top carb.

 

[wook]

Re: Johnson 48 spl running on 1 cylinder

both cylinders have plenty of fire and compression.

 

[Silvertip]

Re: Johnson 48 spl running on 1 cylinder

You need spark, compression, and fuel and everything needs to happen at the right time to make the engine run. You said you have plenty of compression -- but how much is that? How did you check spark? Spark must jump at least a 7/16-inch gap with a good solid snap. Anything less is not good spark. Lastly, if one cylinder is not getting fuel, try squirting some fuel/oil mix into that carb throat. If the engine picks up you identified the problem. Rebuild the carb (both of them since you will be in the area anyway).

 

[71mfg]

Re: Johnson 48 spl running on 1 cylinder

One thing I found this weekend, my top carb. was'nt getting fuel, I had a blockage where the fuel line manifolds into three. My carb was dry and that was the 1st thing downhill.
Charlie

 

[tashasdaddy]

Re: Johnson 48 spl running on 1 cylinder

that would be a good reason. stuck float needle also.

 

[wook]

Re: Johnson 48 spl running on 1 cylinder

it will spark real well from over 1 inch. sprayed gas mixture into carb with very little change. carb looks clean and can pass through all holes clearly. cleaned it any ways with no change. vent is working. putting a rag over top carb to choke out does not have any effect. once i pump up the bulb hard should it stay hard. compression on both cyl. shows to be 100 lb. any input greatly appreciated.

 

[chbailey]

Re: Johnson 48 spl running on 1 cylinder

Check your carbs to see if they are holding fuel. Prolly a stuck float needle (same thing for me) Just had this very same problem with my 97 50hp. Had to rebuild the carbs and still working on the tuning.