90hp 1998

[samchamp]

i hae a 90 hp yamaha that the #3cylinder is not firing.I did a comp.check and all cylinders have the same so i rebuilt the carb changed the spark plugs and rotated the coils.still when i pull the plug wire off the motor does not change the coil is firing and there is gas in the cylinder.any thoughts as what may be wrong

[robert graham]

Maybe bad fuel pump diaphragm causing raw fuel to be sucked directly into #3 cylinder causing very rich, "wet plug" not firing. Remove 2 screws holding on fuel pump, then holding pump(still attached to motor), pump primer bulb to look for fuel coming out of back of pump(if diaphragm is bad). New pump is about $45, very easy to replace. Hopefully this may be your problem and an easy fix!

[samchamp]

1998 yamaha

Thanks for the info i checked the pump like you said and sure enough it leaked

i will be putting a new pump on thanks again

[robert graham]

Thats great, and an easy fix! My motor is a 1999 and this year I just broke down and put a new fuel pump on, although the old one was still fine, but now I use the old one for a spare. When that diaphragm goes bad it will definitely make that cylinder run rich. Good Luck!