MF40 Perkins fouling spark plug

RidgeRun · Sep 17, 2011

Geetings, this is my first entry on the forum.

I have a MF40 with a Perkins 3 cylinder gas engine that instantly fouls the #3 spark plug, it looks oily. Tractor uses some oil but not real bad.

I have owned it for about 14 years. I replaced the valve seals, but did not have much hope when I found that the old ones were still pretty resilient, since they were replaced when the engine had a total overhaul right after I bought it. The overhaul was about 1200 hours ago and included honing the cylinders, rings, new crankshaft, bearings, head reconditioning with valve job, etc.

I tested the compression = all three cylinders 125 psi dry, 140-145 wet. (#3 was 145)
I installed a spark plug 渡on-fouler = no help.

I appreciate your ideas on the cause.

RonL

PoorPlowboy · Sep 17, 2011

First determine if its oil or gas fouled. A long grill lighter with the plug held by tongs will assist. If it flash flames = gas. Slow smoking flame = oil

RidgeRun · Sep 17, 2011

Plowboy,

Thanks, I will try the flame test and post the results.

RonL

SandburRanch · Sep 17, 2011

I don't know what a 渡on-fouler plug is but while you are testing dry the plug well and try grounding it to see if it sparks. If it sparks then check for a vacuum leak at the intake manifold of that cylinder.

kaferhaus · Sep 17, 2011

Intake leak would cause a lean condition, not a fouled plug.

check for spark first. then check for compression If you're getting spark/compression, then it's oil fouled.

A faulty carb would fuel foul them all, weak or no spark would foul only the one, burnt or bent valve would only foul one.

Most likely culprit would be a broken or stuck oil ring.

RidgeRun · Jul 9, 2012

kaferhaus -- you mention a "stuck" oil ring -- anyway you know to try getting it unstuck?

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Sorry, I have not got back to this post in a while.

The buildup on the plug did burn slow, so as Plowboy said "Slow smoking flame = oil"
I've replaced the spark plug(s) and the entire ignition system (Points, condenser, cap, rotor, coil, wires.
I guess my worst fear is probably true - the oil ring.

Hard to accept when the engine was overhauled just about 1200 hours ago and included honing the cylinders, rings, new crankshaft, bearings, head reconditioning with valve job, etc.

Well thanks for all your replies.