HELP............Mark... anybody?

[rontron]

I rebuilt my 1438 months ago and it has been running fine..........recently it started sputtering and I noticed the number one spark plug fuel fouled.......replaced it and it fouled immediately again........disconnected it and it ran worse so the plug was trying to fire.....did a compression check......and I'm getting 125 pounds to it (number one cylinder) and 125 lbs to 3 and 4 and about 108 to number two........so number one cylinder is got good compression.......a real head scratcher........when I pull off all the plug wire at the distributor......get good spark.......pull them at the plugs and good spark.........Hello?

[wizard124]

So, you replaced the #1 plug with a new plug? or just cleaned and replaced it? Was it "running rich" fouled? Or oil fouled?

Assuming you put in a new #1 plug and rich fouled, resistance check the plug wires. They should all read about the same. Pull the cap and clean the rotor and cap contacts.

Sometimes the coil will produce a weak spark but the ignition is bad under compression. When you check spark is it a crackling blue spark (good) or a a flame colored spark (bad).

[majicwrench]

What makes you think plug fuel fouled?? If running rich enough to fuel foul, you would be blowing black smoke out tailpipe.
Keith

[rontron]

thanks for the response................did all that .......cleaned cap and rotor......spark is blue.......only number one cylinder is FUEL fouling ..........like I said compression is good.........and there is little or no smoke coming out of the exhaust.....just doesn't make sense...........

[rontron]

saying the plug itself is FUEL fouled is really not the case I guess because......its trying to fire because if I pull off the wire when it is running it does make a little difference........eventhough its studdering.....no smoke is coming out of the exhaust like I said before......and its only number one cylinder.......I need a rocket scientist

[focodave]

Just grasping at straws here, but could it have something to do with a wiped cam lobe on the exhaust side?
That would still give you a good compression test, but could really screw things up otherwise.
I imagine it is very rare to have a cam lobe go south, but that's all I can think of based on your description of the symptoms and the results of what you have already tested.
It still sure sounds like something is wrong in the ignition system, though......

[majicwrench]

A plug that is fouled will not fire and that cylinder will not contribute. So, plug is not fouled IF that cylinder is producing power ie rpms drop when ign shorted to that cylinder. Pulling wire off plug or cap is NOT best way to kill cyliders, all that voltage has to jump to something but that seems to be a popular way to do it.

SO, do all the cylinder contibute the same?? Or is #1 different?? Again, what makes you think plug is fouling?? Appearance??
THe usualy culprits for rough is things like vac leaks, plugged idle jets etc.
Keith

[So Cal Mark]

when you checked compression, were all of the plugs out of the motor or just the cylinder you were testing? It could be a flat cam lobe, it is fairly common these days. Did you use your existing cams on the rebuild?

[rontron]

when you checked compression, were all of the plugs out of the motor or just the cylinder you were testing? It could be a flat cam lobe, it is fairly common these days. Did you use your existing cams on the rebuild?

yes ..........when I checked compression....plugs were out................the cam couldn't go flat overnight.......this happened over night...........one day it was fine and the next sputtering..........Mark is the DHSA weber carb or intake manifold designed in such a way that more fuel could go into one cylinder than the others?

[FiatMac]

May be a hairline crack in your distributor cap affecting #1. Try a different cap.

[majicwrench]

IF #1 wire is sparking at plug is likely not dist cap, save your time and money.
Again, what makes you think plug is fouling??? Help us out here. Is plug dark?? Do all the other cyl contribute?? It is tough for one cylinder to get a lot more fuel than other cylinders, and if it happened, it would likley be the back (slightly lower) cylinders, and agian, it would smoke.
Keith

[focodave]

rontron,

We need more clues to this riddle in order to help you figure it out.
I know that the questions may be annoying but we are only trying to help, and without being able to see and touch the car, we simply need to ask more questions.
I have some:
Is the "fuel-fouling" leaving just a sooty-black spark plug -- or is the plug wet with fuel when you remove it?
Are you located in an extremely humid climate? (plug wires will arc to surrounding metal if they are leaking and there is much humidity in the air)
If the weather just went from dry to extremely wet when your problem occurred, you may want to run the car at night with the hood open and look carefully for arcs from the plug wire(s). You would also be able to hear the arc.
Are you 100% positive that only plug #1 is fouling?
The beauty of this problem is that the cause may be something obvious, since it happened overnight.

[FiatMac]

IF #1 wire is sparking at plug is likely not dist cap, save your time and money.

Actually, you can have a spark jump a gap outside the engine but it will not jump the gap under compression in the engine. This can happen because the voltage required to jump the gap increases proportionately with pressure. If a fault in the distributor cap or a plug wire serves to reduce the voltage available at a plug to a value that is marginal for the pressure condition in the running engine, you will get a weak spark/erratic ignition on that cylinder while running, but would see a spark when tested outside the engine.

Focodave has a point about the plug wires. Are your wires long enough that you can swap wires between #1 and another cylinder to see whether the problem moves with the wire?

[rontron]

rontron,

We need more clues to this riddle in order to help you figure it out.
I know that the questions may be annoying but we are only trying to help, and without being able to see and touch the car, we simply need to ask more questions.
I have some:
Is the "fuel-fouling" leaving just a sooty-black spark plug -- or is the plug wet with fuel when you remove it?
Are you located in an extremely humid climate? (plug wires will arc to surrounding metal if they are leaking and there is much humidity in the air)
If the weather just went from dry to extremely wet when your problem occurred, you may want to run the car at night with the hood open and look carefully for arcs from the plug wire(s). You would also be able to hear the arc.
Are you 100% positive that only plug #1 is fouling?
The beauty of this problem is that the cause may be something obvious, since it happened overnight.

plug is wet...............humid climate no...................100% sure only plug one is partially firing.........I agree with the obvious thing but what the hell is it........I had a similar problem with one cylinder missing on my 36 ford pickup with a y block in it and when I pulled the plug that wasn't firing the gap was non existant........it had closed inside the engine......figure that one out........I always have these weird things happen to my cars......its something about being rontron

[rontron]

IF #1 wire is sparking at plug is likely not dist cap, save your time and money.

Actually, you can have a spark jump a gap outside the engine but it will not jump the gap under compression in the engine. This can happen because the voltage required to jump the gap increases proportionately with pressure. If a fault in the distributor cap or a plug wire serves to reduce the voltage available at a plug to a value that is marginal for the pressure condition in the running engine, you will get a weak spark/erratic ignition on that cylinder while running, but would see a spark when tested outside the engine.

Focodave has a point about the plug wires. Are your wires long enough that you can swap wires between #1 and another cylinder to see whether the problem moves with the wire?

GOOD IDEA......HAVEN'T TRIED THAT YET........WILL DO TODAY AND GET BACK