black plugs???

[rchevelle71]

what would cause 2 plugs to be black and sooty, but dry, when the other 4 are clean and wet??

Must be a carb issue I would think??

[rchevelle71]

OK,

here is what I found........

I cleaned the plugs, and ran at idle, ran fine, and didnt foul plugs at all, all clean and wet.

Reved up, and #3 got dry and sooty.

Switched top, and middle carbs, thinking now #1 would get sooty if it were carbs, but didnt happen, #3 still dry and sooty.

I have a new coil pack coming tomorrow, gonna try on #3 and see what happens.

[rchevelle71]

had a thought this morning.........

when I replaced the bleed lines, I accidentally took one of them off on that side without paying attention to which way the checkvalve went. I put it on thinking I have a 50% chance of getting it right, if this were backwards, could this cause the black plug at higher rpm, but not at idle?? Turns out, it is really only # 3, 5 looked OK after yesterdays trials.

[SatisfAction]

Rick. I'm not certain if the bleed line would cause the plug in 3 to get black and sooty or not, but then again it could. The check valve should be stationary and not move so whenever you hook up a line it should still only flow one direction. The purpose of them is to keep excess gas off the reeds at idle. If it isn't drawing enough excess fuel than maybe it lead to you plugs bein sooty.

[Jay Smith]

More info please,


Injector are carbed ???

[rchevelle71]

More info please,


Injector are carbed ???


carbed, I ruled out the carb, by switching the top and middle carbs. This started happening around the same time I replaced the hoses.

Thanks,

Rick

[rchevelle71]

Rick. I'm not certain if the bleed line would cause the plug in 3 to get black and sooty or not, but then again it could. The check valve should be stationary and not move so whenever you hook up a line it should still only flow one direction. The purpose of them is to keep excess gas off the reeds at idle. If it isn't drawing enough excess fuel than maybe it lead to you plugs bein sooty.

there are 3 that are stationary mounted in brackets, in the middle of the motor that run from the front(near the reeds) to the cylinders, then 3 more that seem to run betweeen cylinders, one of those are the one in question, not the stationary ones.

[SatisfAction]

there are 3 that are stationary mounted in brackets, in the middle of the motor that run from the front(near the reeds) to the cylinders, then 3 more that seem to run betweeen cylinders, one of those are the one in question, not the stationary ones.

Gotcha..

In that case..

With the lines installed on the block, you should be able to blow air through them, towards the cylinders. With the lines installed on the intake you should not be able to blow any air. Hope this makes sense, lol.

[rchevelle71]

from the diagram, looks like all of the arrows point toward the cylinders, from the reed area, and from the area between the cylinders, I'll attach the pic. One of the 3 in red are in question, cant remember which one I disconnected without paying attention to, but it was definitely one of these 3.

[stvhelm]

electric pump? check pressure should be under 5lb.
do you have the enrichen circuit on the side of the carbs? if that adjusting thumb screw is loose it will flood the lower carbs.

[johnt]

might be something as simple as spark plugs?

[rchevelle71]

electric pump? check pressure should be under 5lb.
do you have the enrichen circuit on the side of the carbs? if that adjusting thumb screw is loose it will flood the lower carbs.

Stock Pump, not electric. Not sure what the enrichen circuit is??, if your talkin about the solenoid for startup, it is electric, and run by the comp on this one, but wouldnt that effect all of the cylinders, remember I swithced the carbs around, and it stayed with the same cylinder.

[rchevelle71]

might be something as simple as spark plugs?

I tried both the BR8's, and the others, BPz8n10, or something like that, that were spec'd for this motor, both do the same thing, also have cleand them several times, and changed them from one cylinder to another to rule that out, always happens on #3, doesnt happen at idle, only when running at higher RPM's, which made me think it was the transition, or high circuits on the carb, but ruled that out with the carb swap.

[j_martin]

If you have a stock pump, a leaking diaphragm will flood one cylinder, I think #3. If you look in the pulse hose and find gas, this is it.

hope it helps
John

[rchevelle71]

If you have a stock pump, a leaking diaphragm will flood one cylinder, I think #3. If you look in the pulse hose and find gas, this is it.

hope it helps
John


what is a pulse hose??

[j_martin]

There is a hose from the fuel pump to the crankcase which provides the vacuum and pressure pulses that drive the fuel pump.

If the diaphragm is cracked, fuel goes directly into the crankcase (one cylinder only) from the fuel pump.There are 3 hoses on the pump. One coming in from the oil mixer, or directly from the fuel tank if the oiler is removed. One goes to the carburetors. The other one is the pulse hose.

Mercury parts express is down, so I can't draw (clip and paste) you a picture.

hope it helps
John

[rchevelle71]

There is a hose from the fuel pump to the crankcase which provides the vacuum and pressure pulses that drive the fuel pump.

If the diaphragm is cracked, fuel goes directly into the crankcase (one cylinder only) from the fuel pump.There are 3 hoses on the pump. One coming in from the oil mixer, or directly from the fuel tank if the oiler is removed. One goes to the carburetors. The other one is the pulse hose.

Mercury parts express is down, so I can't draw (clip and paste) you a picture.

hope it helps
John

Thanks,

I'll look it up at go-fast.

[rchevelle71]

OK John,

Which Hose:D

[stvhelm]

what year is your motor? The enrichen valve (#14 in your chart), does yours have a thumb screw adjuster on it? may just need to snug it up. it will drain gas from top carb into lower carb if its not right.

[rchevelle71]

what year is your motor? The enrichen valve (#14 in your chart), does yours have a thumb screw adjuster on it? may just need to snug it up. it will drain gas from top carb into lower carb if its not right.

Dont think it has a thumb screw, motor is a 95, but I'll check. It wasnt the fuel pump, or the bleed valves, so its worth a shot. it does have an extra port on it, that wasnt plugged, I thought that would cause a vacuum leak, so I capped it, guess it could be that, but why only cylinder 3??

[stvhelm]

somehow I thought you had a 2.4. maybe from another post i remember. thats a commmon thing with the 2.4. your valve works a little different just make sure the hoses are connected to there correct location. on your diagram on the bottom left it shows where to connect those hoses. also like martin said check the diaphram. that will definetly pull fuel if its leaking.

[rchevelle71]

somehow I thought you had a 2.4. maybe from another post i remember. thats a commmon thing with the 2.4. your valve works a little different just make sure the hoses are connected to there correct location. on your diagram on the bottom left it shows where to connect those hoses. also like martin said check the diaphram. that will definetly pull fuel if its leaking.

blew up the 2.4, dont wanna do the same to this one, hoses are connected, but like i said, there is one nipple next to the fuel in connection, that didnt have anything connected, when i put my thumb over it, it seemed like it was pulling vacuum, so i capped it, diagrams dont show a cap on it, so this could be aproblem.

[j_martin]

OK John,

Which Hose:D

It's not on that diagram, but the fuel pump is dotted. Must be on the diagram that has the fuel pump. It would be a third hose on the fuel pump.
John

PS Found an XR4 diagram, should be the same fuel pump.

[rchevelle71]

It's not on that diagram, but the fuel pump is dotted. Must be on the diagram that has the fuel pump. It would be a third hose on the fuel pump.
John

PS Found an XR4 diagram, should be the same fuel pump.

yeah,

I found it, but on this motor goes to #6.

Ran it at high RPM, then shut off, and disconnected hose, no sign of fuel, not even a fuel smell??

[j_martin]

yeah,

I found it, but on this motor goes to #6.

Ran it at high RPM, then shut off, and disconnected hose, no sign of fuel, not even a fuel smell??


I guess my next step would be to put a timing light on #3 and see if it keeps flashing at WOT under load.

If one plug misfires, gotta be switchbox or coil (or associated wires)
If 2, could be trigger
if 3, stator or switchbox.

hope it helps
John

[rchevelle71]

I guess my next step would be to put a timing light on #3 and see if it keeps flashing at WOT under load.

If one plug misfires, gotta be switchbox or coil (or associated wires)
If 2, could be trigger
if 3, stator or switchbox.

hope it helps
John

Havent checked that under load, but have checked at idle.

No switchboxes, has ECU, new coil, and have switched coil with other cylinders. new stator. by trigger, i am assuming you mean the crank position sensor, I havent checked that, but there is only one, and it seems fine on the other cylinders, I had the flywheel off for the stator replacement, guess something could have gone wrong at that point.

[j_martin]

I didn't know that there was an ECU on a carb'd motor.

At any rate, either a spark gap test, or testing with at a light under load is needed to find a stress misfire. If you already swapped out all the parts for that hole with no change, and the coil is driven by an ECU, it'd have to be the ECU. I wouldn't change it until I verified that either the spark was weak or at the wrong time with a timing light. (You would get a slow sooty fire if it was sparked late)

hope it helps
John

[rchevelle71]

I didn't know that there was an ECU on a carb'd motor.

At any rate, either a spark gap test, or testing with at a light under load is needed to find a stress misfire. If you already swapped out all the parts for that hole with no change, and the coil is driven by an ECU, it'd have to be the ECU. I wouldn't change it until I verified that either the spark was weak or at the wrong time with a timing light. (You would get a slow sooty fire if it was sparked late)

hope it helps
John

xactly what i was thinking, I havent put a new coil on that cylinder yet, but have one in the truck, will try that next.

[rchevelle71]

got it fixed, although it still needs some tweaking from me monkying with carb swaps and chit. I should have done these seperate, so I had a good answer of what it was, but I took the vacuum cap off of the enrichener valve, and also put the new coil on, and now its fixed. I didnt just put the new coil on, I put the new one on 3, and put the #3 coil on #6(since I new #6 wasnt that great, and the reason I ordered a coil in the first place), well, #6 is still clean, so I think it was just me being stupid, and capping a vacuum port that shouldnt have been capped.

[rchevelle71]

forgot to mention........

Thanks to all for your input.