bobgritz
Petty Officer 2nd Class
- Joined
- Sep 22, 2009
- Messages
- 185
My 1983 Johnson 15hp engine has developed a hard starting and stalling problem. When cold and first starting, it floods easily and you can only pull out choke briefly. If it doesn't start immediately it becomes saturated with fuel and it is very difficult to restart. It is electric start and I must turn over for at least 20 or 30 separate (lengthy) attempts before all excess fuel residues have been purged. If you pull choke again forget it ... it becomes super saturated. As soon as you get it going, you need to throw it into gear and rev it up high to keep it from stalling. The engine is ?coughing? or misfiring until the excess fuel is consumed. After 30 or 40 seconds of coughing, both cylinders kick in and it seems to run well. But, if you shut the motor off for just a few minutes and try to restart it, it is flooded all over again.
I obviously assumed it was the float and pulled the carb, checked float position, blew out the ports with compressed air and reinstalled with same result. Next, I bought carb rebuild kit, pulled all sealed plugs, blew all ports, installed a new float, replugged, etc. and reinstalled ... same exact problem. Thinking the carb may have a deeper problem I removed a carb from a backup motor but, got the same result.
I began to wonder if it was a mechanical/electrical issue and not a fuel problem. As a test, and with the engine cold and running choppy, I pulled each plug wire and noticed that the top cylinder had little effect on the performance. When you pulled the bottom wire the engine would stall immediately. It would slow slightly when pulling the top wire but it was obviously not helping the initial cold/start operation and this seemed to point to why it had trouble idling.
The next thing I checked was compression. It has 110 in each cylinder.
I switched coils (top to bottom) but got the same problem. I even tested a coil off the parts motor but got the same result.
Swapped spark plugs then bought new plugs ? same result.
Did a simple visual spark plug test and the arcs looked strong.
Swapped plug wires ? same result.
I started to think it was the powerpack so I swapped it with the powerpack off the parts engine ? same exact result.
Here?s what I think. Since there is an obvious problem with a lack of combustion in the upper cylinder, the flooding is not conventional flooding (i.e. stuck float) but it is rather a buildup of fuel in the upper cylinder which is not completing its burn process and the cylinder (and crankcase) become saturated with excess fuel.
The only odd thing that I notice is that when I pull the plug wire on the upper spark plug (while running) there is a large arc (spark) at the coil. In other words, when the plug wire/boot is pulled (off the spark plug), the homeless spark has no where to go and ?jumps? from the coil wire/boot to the grounding bolt (where the coil is attached to the engine). Perhaps this is normal. After all, the spark needs to find a home, right or wrong?
I just pulled the flywheel and everything looks like new. Nothing obviously wrong jumps out but could it be something less obvious here.
I could really use some ideas ? I have never been this stumped before. All I can think of is either a timing issue or perhaps a reed valve issue.
I obviously assumed it was the float and pulled the carb, checked float position, blew out the ports with compressed air and reinstalled with same result. Next, I bought carb rebuild kit, pulled all sealed plugs, blew all ports, installed a new float, replugged, etc. and reinstalled ... same exact problem. Thinking the carb may have a deeper problem I removed a carb from a backup motor but, got the same result.
I began to wonder if it was a mechanical/electrical issue and not a fuel problem. As a test, and with the engine cold and running choppy, I pulled each plug wire and noticed that the top cylinder had little effect on the performance. When you pulled the bottom wire the engine would stall immediately. It would slow slightly when pulling the top wire but it was obviously not helping the initial cold/start operation and this seemed to point to why it had trouble idling.
The next thing I checked was compression. It has 110 in each cylinder.
I switched coils (top to bottom) but got the same problem. I even tested a coil off the parts motor but got the same result.
Swapped spark plugs then bought new plugs ? same result.
Did a simple visual spark plug test and the arcs looked strong.
Swapped plug wires ? same result.
I started to think it was the powerpack so I swapped it with the powerpack off the parts engine ? same exact result.
Here?s what I think. Since there is an obvious problem with a lack of combustion in the upper cylinder, the flooding is not conventional flooding (i.e. stuck float) but it is rather a buildup of fuel in the upper cylinder which is not completing its burn process and the cylinder (and crankcase) become saturated with excess fuel.
The only odd thing that I notice is that when I pull the plug wire on the upper spark plug (while running) there is a large arc (spark) at the coil. In other words, when the plug wire/boot is pulled (off the spark plug), the homeless spark has no where to go and ?jumps? from the coil wire/boot to the grounding bolt (where the coil is attached to the engine). Perhaps this is normal. After all, the spark needs to find a home, right or wrong?
I just pulled the flywheel and everything looks like new. Nothing obviously wrong jumps out but could it be something less obvious here.
I could really use some ideas ? I have never been this stumped before. All I can think of is either a timing issue or perhaps a reed valve issue.
