Spark Plugs Failing Or Bigger Issue???

[HighTide]

Another first for me today. My oldest unit, now 4 1/2 years old, is a Vanguard 18 hp with a 5.6 gpm @3,500 pump. Just had unit tuned up in Feb. Today after 5 minutes of work, it shuts off. It doesn't restart at all nor does it comes close to starting again. Checked oil, gas, air filter, fuel filter -- all right where they need to be and all recently changed or new. Decided to pull both plugs to see that they are VERY worn and black after only a couple of months work. I changed them out with a couple new Champion plugs and it cranked right back up. Sweet!

Not so fast -- after 2 more hours of work the machine had hard time starting back up after I turned it off and when running it sputtered badly and I see a little dark smoke from exhaust. I pull both plugs and the 2 hour old plugs are all black at the business end. I clean the new plugs up a bit and it fired right back up until an hour later and it sputter time again.

What is going on here? Thanks!

 

[Russ Johnson]

Was the air filter recently serviced? Some people over oil the foam element, so the oil gets pulled into the paper and clogs it up. I do not recommend oiling the foam at all.

 

[HighTide]

The air filter was recently replaced. I have never added oil to the air filter.

 

[Tony R]

Oil getting past rings and fouling plugs.
Some kind of an air restriction causing a rich condition. Weak spark not burning all of the fuel. Just throwing out some ideas.

 

[HighTide]

I replaced the air filter anyway even thought it didn't need it. Thought it could have something to do with my choke but it doesn't appear so. I ran the unit for half a day today and it ran rough for 2-3 minutes three times today at random times, but usually a few minutes after a re-start. Each time it seemed to get through it and I go back to work. Hmmm.

 

[scottwash]

I replaced the air filter anyway even thought it didn't need it. Thought it could have something to do with my choke but it doesn't appear so. I ran the unit for half a day today and it ran rough for 2-3 minutes three times today at random times, but usually a few minutes after a re-start. Each time it seemed to get through it and I go back to work. Hmmm.

Check to make sure u have the right plugs, your new plugs could not be getting hot enough. Not the right heat range. Adjust your carb air screw, turn it out. Then lastly check your compression