#4 spark plug fouled. Temperaturw differences between plugs

[dwkfym]

My #4 plug is always sooty black when I pull it out. The other plugs are normal. This happens within 15 mins of idling. Also, my #1 plug is cool enpugh to touch, and the plugs get hotter as they get closer to the tramsmission. #4 plug is hottest to the touch.

Points are set around .020. I ordered new plug wires, but im not sure if that is the culprit.

I am thinking thr #4 cyl is missing and that my cooling channels to that end of the motor are clogged somewhere.

Background-- boat and enginr got flooded last year. Had to replace all electricals and rewire engine. Havent left dock yet-- just did the last oil change. Had marvel mystery oil at the valves (via plug hole) and little bit in the fuel. Running without thermostat amd with manual valve at the bypass. Muriatic acid flush done mid season last year.

Anything else that could be causing these symptoms? Any way to clear coolant passages without engine disassembly?

[JOHN COOKSON]

A compression check would be a good idea since the engine was flooded (with water?). There may be stuck valve in #1 cylinder.
Maybe #4 plug is not good. Try swapping the plugs between cylinders and see if the trouble follows the plug.

TRUE GRIT

[joe_db]

Hmmmm.......
#4 usually will foul first because it is colder than the others in my experience. Odd that it is the hottest one
Is it carbon or oil fouling? Carbon = dryish black, oil is wetter.

[Dave Neptune]

Things seem a bit backwards as far as your plug temps. If #4 is fouling it should be the "coolest" to the touch.

Before doing to much fiddling check you spark at the # 4 plug or if it is difficult any other plug will be OK. You should see a crisp blue flash, if it is pale or yellowish no good.

And if the spark is good start it and try leaning the idle by "opening" the idle air screw about a half of a turn and see if the idle becomes smoother. The average setting on most of these beasties is 1 1/2 turns off the seat. Remember that the screw adjusts the amount of air not fuel so out is lean and in is rich.

Another important and often over looked part of the ignition system are the "spark plug boots" the "BOOT" part needs to fit snug on the plug ceramic and should have no cracks. The boot ceramic relationship is what controls the heat radiated by the plug so they are important as far a good plug temps. A good idea is to coat the inside of the boot with some dielectric grease to aid in not sticking, tears in the boot and good contact for the insulating job the boot does to maintain good plug temps.

Dave Neptune

[dwkfym]

That is why I am thinking #4 is missing - firing every once in a while. Brand new plugs. its black, sooty, carbon fouling.

I can see one of the valves in #1 moving. The plug comes out looking new still (I haven't run it long enough for it to get grey yet) Can I move my head around and see the other valve at #1?

Do you think removing the thermostat might make it so cool that i can still touch the #1 spark plug, and that it might ? Headed to the boat soon.

[joe_db]

misfire makes plugs cold.
BTW - we mean the aft plug when we say #4. Is that what you mean??

[JOHN COOKSON]

I would definitely change out the distributor cap and rotor if you haven't done so recently.

TRUE GRIT

Edit: Is #1 plug firing or not? Start the engine and pull the wire off #1 and see if there's any change in the way the engine runs.

[dwkfym]

Yes #4, transmissioj side plug.
I will try pulling #1 while its running

[dwkfym]

just wanted to update - my distributor, rotor, and points are brand new.

[sastanley]

So, if you have plugs that are cool, maybe the timing is off...did you think about resetting everything with regards to timing and make sure you have the plug wires correct 1-2-4-3?

[dwkfym]

plug wires are correct. So indeed timing might be causing this? I will redo timing as soon as I can.

[joe_db]

I don't see how timing would change the temp of just ONE spark plug

[dwkfym]

I don't see how timing would change the temp of just ONE spark plug

Its gradual. #1 being cooleest, with #4 being hottest. Each plug gets hotter and hotter

[joe_db]

Before you do anything else, do a power check. Use oven mitts and while the engine is running slowly under load, remove and replace the wires one by one. Note the RPM drop for each cylinder. Don't forget the glove! Not that I did that - more than once

[Dave Neptune]

When did the new distributor parts go in? Before of after the present starting issue?

Dave Neptune