1999 90 hp ficht

[wayne campbell]

i am fouling plug #4 and cant find out why please help

 

[jegervais]

Re: 1999 90 hp ficht

On that engine, the crankcase pressure and vacuum pulses "drive" the fuel & oil lift pumps. One bank of cylinders works the fuel pump and the other bank works the oil pump. I seem to be having a bout of "C.R.S." right now and can't remember which bank works which pump, but it's certainly worth looking at the pulse lines of the oil lift pump. The oil lift pump is the "round-shaped" metal bodied pump, remove the 2 hoses that attach to the crankcase cover and run a q-tip swab inside the hose. It should come out clean. Any amount of oil would indicate the oil lift pump diaphragm may have failed. This may be leaking extra oil into a cylinder, causing the plug fouling you're experiencing. You can also pressure test the diaphragm by hooking up a pressure tester to each pulse line. Pressurize to 10 psi - any loss of pressure indicates a ruptured diaphragm. Replace the lift pump if it tests bad. If you're not comfortable doing this type of work, the best advise anyone can give you is to find a qualified service dealership.<br /><br />Hope this helps.<br /><br />-John<br /><br />BTW - If you don't have the factory service manual, get one. Order thru your local Johnny/Rude dealer, p/n is 787024.

 

[Scale Performance]

Re: 1999 90 hp ficht

Wayne, how long has it been since your plugs were changed? i have seen plenty of plugs starting to foul out between 50-100hrs, depending on how you run your engine. if that plug is the only one that has alot of carbon growth, it may have been indexed wrong. if it is wet lookign you might have a fuel lift pump problem, like described by John.. or you might have a fuel injector going out. simple check, make sure all of teh spark plug leads are on tight and the primary leads going to the ign. coils are on tight, have seen probs there too causing fouling,,<br /><br />good luck..<br />SP