1994 P50 Bottom Cylinder wont fire

[dennismenace111]

At idle, running on the muffs, it runs really rough... when I pull the plug wires, the bottom wire has no affect when its pulled... the other two kill the engin when I pull them individually.

Did a compression test, and all 3 were about the same, within 5 psi of each other...changed the plugs...no joy... when I pull the plug wire, there is a hot spark to the plug.

I know this isnt a heck of alot of information, but does anyone have any suggestions on what to try next?

[rodbolt17]

if you have spark and compression it only leaves fuel.

[99yam40]

fuel pump could be leaking into #3 crankcase, vacuum leak, or carb has a problem
Too much fuel or too little screws up the air/fuel ratio and will not let the cylinder fire properly

[almetelo]

Already seen that pic on a same model of a friend...

1994 P50TLRS Yamaha Outboard CARBURETOR Diagram and Parts

Check parts:

#42 gaskets
#43 Diaphragm

[dennismenace111]

Any way that you know of to test the fuel pump for leaks?? The primer bulb gets firm but never gets totally hard.... and no, Im not quoting my wife!...would that indicate a leak in the fuel pump?

[almetelo]

If the primer bulb gets hard I dont think the problem is on fuel pump but better way is test it intead of guessing, use a vacuum / pressure gauge.

Have you checked my sugestion above?

[99yam40]

he said it gets firm but not hard, so yes the pump could be the problem.

Unbolt pump from motor but leave hoses hooked up.
pump primer bulb and see if fuel comes out of the pulse port

[dennismenace111]

he said it gets firm but not hard, so yes the pump could be the problem.

Unbolt pump from motor but leave hoses hooked up.
pump primer bulb and see if fuel comes out of the pulse port

Excellent idea...thanks.. I ll give that a try in the morning...