Nr 3 Cylinder

[Anonymous]

my granddaughter has a '65 Mustang with a 200ci inline six engine; this engine is actually a '66; because, a local Mustang Shop replaced it a couple of years ago; now, it has the EXACT same problem the previous engine had; that is, that the nr. 3 cylinder fouls out the spark plug. When you pull the plug, it is full of oil, and the center electrode is shorted to the ground part of the plug. What gives with this particular cylinder?

 

[gtm1086]

Luck of the draw I guess. If #3 is coming out oil fouled I would suspect bad valve guide seals. If it is fuel fouled you could have a carb that is flooding. #3 is in line with the carb.

 

[addo]

It could well be low compression in that cylinder. Can you perform a compression check with and without a dessertspoon of engine oil squirted into each cylinder? (Have the motor at running temp first, then pull all the sparkplugs, ground the coil.)

Some results would help diagnose your complaint a little more.

Regards, Adam.

 

[Anonymous]

My motor is fresh and it does the same thing.

 

[Anonymous]

I had a cracked head that would foul out the back 3 plugs. Do the first 2 plugs in your case, show any signs of abnormal plug readings? Possible beginnings to what is happening to the 3rd plug.?

 

[mugsy]

I had the same problem on my 1965 Mustang, but it was #5 cylinder that would foul. But same exact symptoms. I found out that the valve stem seals were shot. New ones are soft, the ones I took off were rock hard. You "should" be able to take off the valve cover and poke at the little black seal between the valve spring. If it is flexible, then start looking at the rings, etc.

I replaced the seals with the head on the engine in the car. Long story short: use compressed air to hold the valves up, buy or rent a one sided valve spring compressor, use the handle of a large screw driver to loosen the keepers from the retainer, and keep a magnet handy to pick up the keepers.

tanx,
Mugsy

 

[Anonymous]

It's mainly nr. three; occasionally nr. four shows signs of fouling after 4 or 5 months; but, nr. three needs to be pulled at least every three weeks, if not sooner.
As for changing out the valvestem seals, not on this car; but, on other cars, I've done so by removing the spark plug, and sticking about 18 inches or so of clothesline rope in the cylinder; then, bringing the piston up until it stops; that keeps the valves up tight, and facilitates easy disassembly.

 

[Anonymous]

petrokat,
Can you swap a couple of the plug wires around and see if the problem follows the wire?
Also check the spark plug wire for other interference along its way to the plug.
Also you might check the ditributor cap for soundness.
FWIW DaveP

 

[80broncoman]

The rope trick works quite well, just don't forget to put a large knot on the end so you dont end up with the whole rope inside the cylinder.