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30LX Fouled Plug but have good compression

D

dhelmke

New member
I have a 3.0 LX and the #1 plu

I have a 3.0 LX and the #1 plug gets fouled after a short time on the water even after installing new plugs. I tested compression and all cyl are good within 5psi 155-160. Tested the electric parts that I can [all passed]and wondering if the Ignition Module can cause one plug to foul. Dist cap wires and rotor new this spring and looks good so down to the module or ??
Any thoughts appreciated
Dave H
 
"Sounds like a bad oil control

"Sounds like a bad oil control ring or bad valve stem oil seal to me.
It can happen, and yet compression is still good.
How many hours on it?

Rod"
 
"Give us more details on ignit

"Give us more details on ignition system and testing

What year?
What type of ingnition?
WHat tests were performed specifically and what were the results specifically.

What engine temps are you seeing?

If too cold that could be an issue. What spark plugs are you using, Brand and part number? what is the gap?

Typically with an electronic igmition if you have spark it does not matter at that point the condition of the internal parts of the distributor. The only deciding factors would be rotor, cap, wires and plugs. Spasrk is spark and it only gets distributed. Of course the condition of the spark is important. That is where the ignition type comes into play. different ignitions have different results.


Details....details.......details.......we like details...."
 
"Thanks for all the input, her

"Thanks for all the input, heres more information
The motor is a 1996 but not sure how many hours but approx 500-800 -bought the boat used in 2000 the owner only used it a a few times a year.
The plug has a medium brown build up on the center that can be cleaned off but there is no indication of oil or a wet foul. Thought it was a head gasket leak with water but no indication on this either- should I put vaccum test on that cylinder.
Electronic ignition - original
I have a manual from Clymer and tested the following with ohmmeter or volt meter
Plug wire resitance same as a other similar length wire and is new this spring [maybe will change to other plug wire to see if it moves the fouling]
New battery
Pickup coil tested = OK with ohmmeter
Distributor cap/rotor look good and no tracks or burns- new this spring but may try new set?
Spark intensity test [used adjustable gap tool set to 3/8"] with #1 looks similar to other plugs
Ignition Coil checked per manual with ohmmeter and OK
When the problem occurs at idle speed while trolling I start to loose RPM from the speced 650-700 down to 450-500 rpm and then when increasing to 900-1200 RPM the motor runs very rough almost like it is cross firing which is why I thought maybe the module was the problem ?
Plug wires not touching so no cross sparking between wires
The only way to keep it running at idle when this happens is to reset idle screw up a little back to 650rpm but it still runs rough. The odd thing is it will smooth out randomly at idle speed and at anything higher than 1200-1400rpm it seems to run good and is not rough.
Thanks for the help
Dave H"
 
Dave:

Are you using any f

Dave:

Are you using any fuel octane booster or other cheap additives? Boosters will foul plugs but usually all of them. Replace the plug since it may have internal damage that is creating your problem. Check the wires for leakage using a spray water bottle in the dark; mist each wire and then mist heavily between them along their length. If there is leakage you will see it jump from the wire.
 
"Dave,

One thing that come

"Dave,

One thing that comes to mind that can create the intermittent running problem could maybey the tach on the way out/faulty.

Dissconect and see if you still have this rough running problem.

It is still odd for that to create fouling on 1 cyl so I could be wrong.

Just another thing to eliminate i you trouble shooting - anyone jump in if you think I'm on the wrong path..."
 
"David...

I'm thinking

"David...

I'm thinking along with Rod's post up above. The oil rings will let oil up into the combustion chamber for the plug to burn, but won't have anything to do with a compression test. Thats what the compression rings are for. The medium brown build up on the center electrode of the plug is oil. Oil usually only looks wet and gooey in a 2 stroke motor. On a 4 stroke, its that medium browm build up that you can pick off with your finger nail. Bad valve seals will let oil into the comb. chamber usually at idle. After idling for about 3 mins. give a hard exceleration and see if you can detect blue hazey exhaust. That would be oil let in by the valve seals. But with only one plug showing a problem, there probably won't be enough oil in the exhaust to see it. If you can see blue exhaust behind the boat during all other times of travel, that would be your oil rings. Again though, with only one plug, the chances of seeing anything is remote. Slipping a new set of valve seals on all the valves isn't a huge job and can easily be done at home, if you have access to an air compressor. Put some new ones on all of them and see if the plug stays clean, if not, you may be looking at rings. In that case, you may want to spin a new plug in every once in a while if the motor still runs good.

Wrench"
 
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