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black spark plugs, worse and worse

M

mywizbo

Member
Hi AC people...if anyone can help and pls give me a troubleshooting/diagnosis plan it would be great.

black spark plugs I've been dealing with this the whole time I've had the d17, and now it's gotten so much worse that I can barely use it. When I put fresh plugs in, it'll run reasonably well for a while and then I'm usually not able to get rpm's with more throttle, and then it'll just die entirely. If I change the black plugs out for new ones, I restart the cycle. But now they're fouling up really fast. A few people told me it's running rich, but I took the air filter off for a while and same problem, and also, it seems to run a little better with the choke engaged a little bit - which I thought was weird b/c that would indicate that it's running lean right? I do get a fair bit of black smoke from the exhaust as well.
Any suggestions?
 
Your running extra rich on the mixture.
Taking the air cleaner off isn't going to do
anything to reduce the amount of fuel going
into the intake from the carb. Not knowing
what has been done to it at this point, I'm
going to treat this as if this is a random
problem that just started without someone
adjusting the carb wrong. When a tractor over
fuels like yours it's because too much fuel
is getting into the float bowl. There are two
main causes for this. #1 the float needle
isn't sealing up good against the needle
seat. To fix this, take the carb apart, clean
the needle and and needle seat. If either
doesn't look perfect afterwards, replace them
with new ones from a carb kit. Second reason
a carb will overfuel like this is because the
float has started to leak and is now sitting
lower in the bowl and not stopping the fuel
flow. The float can be repaired, but that
causes the float to be heavier and you have
to adjust the float level differently. In
your case if the float has fuel inside, I
recommend buying a new float as it will be
way easier to set it at the right height.
Remember, my $.02 is going off of an
assumption that this randomly started and not
started after someone adjusted the carb.
 
I'm including pictures of what a good needle and seat should look like. Note that the black rubber tip to the needle doesn't have any deformation and that the small inside hole of the seat doesn't have any pitting or gouging. Both are a must to get the fuel to stop flowing at the proper height.
cvphoto155930.jpg


cvphoto155931.jpg


cvphoto155932.jpg
 
(quoted from post at 11:27:29 06/05/23) Your running extra rich on the mixture.
Taking the air cleaner off isn't going to do
anything to reduce the amount of fuel going
into the intake from the carb. Not knowing
what has been done to it at this point, I'm
going to treat this as if this is a random
problem that just started without someone
adjusting the carb wrong. When a tractor over
fuels like yours it's because too much fuel
is getting into the float bowl. There are two
main causes for this. #1 the float needle
isn't sealing up good against the needle
seat. To fix this, take the carb apart, clean
the needle and and needle seat. If either
doesn't look perfect afterwards, replace them
with new ones from a carb kit. Second reason
a carb will overfuel like this is because the
float has started to leak and is now sitting
lower in the bowl and not stopping the fuel
flow. The float can be repaired, but that
causes the float to be heavier and you have
to adjust the float level differently. In
your case if the float has fuel inside, I
recommend buying a new float as it will be
way easier to set it at the right height.
Remember, my $.02 is going off of an
assumption that this randomly started and not
started after someone adjusted the carb.
Click to expand...
So this has always been an issue since I bought it off a guy last year, but it's just gotten worse and worse to the point that now I can barely use it for 30 min on new plugs until they foul up and stop the tractor from running. My thinking with removing the air filter was that maybe it was dirty and not letting enough air into the mixture...also, why if I'm running rich, which is what makes sense to me from what you and others say, would the engine run better (with new plugs in) when it's choked a little bit? When I'm choking it I'm just letting even less air in...So either way, what I'm hearing from you is that I've got a carb problem, and I've got to get it open and clean it out and see what's going on in there. Thanks a lot, I appreciate the advice, and pictures. It'll take me a while to get to this and I may have to just swap out plugs to get the work done I need for a while here (I've got a field to mow and bale), but I'll update when I can. Thanks again. Most guys probably would say a carb cleaning is a winter job I guess.
 
There are two kinds of 'black' plugs. Are
they burned, dry, and dusty black, or more
rich, dark, possibly even slightly goopy
black? First case is running too rich.
Second case is oil bypass. How's the engine
apart from this issue? Does it start easy
with loads of power? A compression test
might tell a lot.

Once you're sure the carb's adjusted right,
make sure you have the right plugs in
there. A heat range too high or too low can
sometimes make a big difference. Often
going up a heat range on the plugs (hotter)
can help burn off deposits better.
Especially on some of these old tractors
that were meant to be worked hard, and now
are on only light duty utility work.
 
(quoted from post at 16:50:00 06/05/23) There are two kinds of 'black' plugs. Are
they burned, dry, and dusty black, or more
rich, dark, possibly even slightly goopy
black? First case is running too rich.
Second case is oil bypass. How's the engine
apart from this issue? Does it start easy
with loads of power? A compression test
might tell a lot.

Once you're sure the carb's adjusted right,
make sure you have the right plugs in
there. A heat range too high or too low can
sometimes make a big difference. Often
going up a heat range on the plugs (hotter)
can help burn off deposits better.
Especially on some of these old tractors
that were meant to be worked hard, and now
are on only light duty utility work.
Click to expand...
I'm using it pretty hard. I pulled a two bottom plough with it, an 8 ft planter, etc.
I'm attaching some pics of the plugs that I just took out. I'm not sure you'll be able to see them clearly, but maybe if you enlarge the pics. I think they're dry dusty black, but I'm not certain that it's not a bit goopy wet black sometimes.
mvphoto106424.jpg


mvphoto106425.jpg


mvphoto106426.jpg

[/img:a2de31445c]
 
The pics are a bit out of focus toe and hard
to tell, but they look dry and sooty. Oil
fouled plugs will still have oil on them and
will be shiny wet. Here's a pic of an oil
fouled plug. Im not saying it isn't possible,
but I've never seen oil fouling on every
cylinder at once. In a previous post you said
that you are getting black smoke with it,
that smoke is going to have a strong exhaust
smell to it and cling to you and your clothes
for a fair amount of time. Oil fouling would
produce blueish smoke that smells like hot
oil dripping off of a valve cover onto a hot
engine. I can't say for sure why overfueled
engines need to be choked to run bette, but
it might have to do with the air speed coming
into the motor being slower and not being
able to pick up as much fuel on the way
through the carb.
cvphoto156031.jpg
 
CHAMPION spark plugs ??? That in itself is a problem. Most D-17's use AC Delco R45 XL or R45 XLS spark plugs which are 3/4" reach threads. Are you using the correct length plugs?? Adjust the carburetor main load jet at wide open throttle by turning it IN until the engine begins to stumble and then back out 1/4 turn at a time until it runs good when you drive it under load. D-17's have TWO carburetors !! WHICH ONE do you have ??????
 
These plugs are autolite 303's. when I bought it it had champion j8c's in there. It's a series I d17, but I can't be sure the carb is original. I'll see if I can get a number off the carb...
 
The main load jet (the one in front under the carb I believe) is almost all the way open. I did the adjustment that you mentioned after reading this in the manual, and when it's under load I found that the main jet needed to open almost all the way - now this could obviously change if I have problem inside the carb.
 
I'm pretty sure they're dry and sooty. I may have seen one or two of them with this oily look, but I think the main issue is the overfueling causing the rich mixture. I've got to get into the carb and see if I can clean it out.
 
Just because it is an early D-17 doesn't mean it uses SHORT 3/8" spark plugs. MANY have had the cylinder head replaced in the last 50+ years and then they require the LONG 3/4" reach plugs. VERIFY which plug length you need.
 
(quoted from post at 18:34:05 06/06/23) Just because it is an early D-17 doesn't mean it uses SHORT 3/8" spark plugs. MANY have had the cylinder head replaced in the last 50+ years and then they require the LONG 3/4" reach plugs. VERIFY which plug length you need.
Click to expand...
Verify by just getting an AC Delco R45 and seeing if the thread screws all the way in? Sorry for the stupid question if that should be obvious to me - I don't have a lot of engine experience and I'm figuring it out as I go...btw I looked up the AC Delco R45 xl and it's says the thread reach is only .37 inches. If I do need a longer plug then I'm using are you suggesting that could contribute to the quick fouling?
 
(quoted from post at 20:52:55 06/06/23)
(quoted from post at 18:34:05 06/06/23) Just because it is an early D-17 doesn't mean it uses SHORT 3/8" spark plugs. MANY have had the cylinder head replaced in the last 50+ years and then they require the LONG 3/4" reach plugs. VERIFY which plug length you need.
Click to expand...
Verify by just getting an AC Delco R45 and seeing if the thread screws all the way in? Sorry for the stupid question if that should be obvious to me - I don't have a lot of engine experience and I'm figuring it out as I go...btw I looked up the AC Delco R45 xl and it's says the thread reach is only .37 inches. If I do need a longer plug then I'm using are you suggesting that could contribute to the quick fouling?
Click to expand...
I'm saying that use of the WRONG plug sure isn't helping your problems. I don't KNOW that you are using an incorrect plug, but I know you could be. It's happened before.
 
(quoted from post at 05:27:03 06/07/23)
(quoted from post at 20:52:55 06/06/23)
(quoted from post at 18:34:05 06/06/23) Just because it is an early D-17 doesn't mean it uses SHORT 3/8" spark plugs. MANY have had the cylinder head replaced in the last 50+ years and then they require the LONG 3/4" reach plugs. VERIFY which plug length you need.
Click to expand...
Verify by just getting an AC Delco R45 and seeing if the thread screws all the way in? Sorry for the stupid question if that should be obvious to me - I don't have a lot of engine experience and I'm figuring it out as I go...btw I looked up the AC Delco R45 xl and it's says the thread reach is only .37 inches. If I do need a longer plug then I'm using are you suggesting that could contribute to the quick fouling?
Click to expand...
I'm saying that use of the WRONG plug sure isn't helping your problems. I don't KNOW that you are using an incorrect plug, but I know you could be. It's happened before.
Click to expand...
Ok, so the plot thickens.
I put a 3/4" ngk plug in the d17 that I found on the floor of my truck. I don't know what kind of plug it is, but just that the thread was the right size and it was 3/4" to test if it fit. It screwed all the way in pretty easy. I'm putting pics of the autolite 303 I took out and the ngk I put in. You can se the ngk is black from the inside of the cylinder and the clean part where the thread wasn't blackened
mvphoto106483.jpg


mvphoto106484.jpg


mvphoto106485.jpg
 
(quoted from post at 18:17:12 06/07/23) weak spark would cause the fouling of my plugs?
Click to expand...
Could be. I would also expect a weak spark to miss-fire under load and you haven't said anything about that. If you were able to fully thread in a 3/4" long plug, that is the CORRECT length because if it was too long it would smash the electrode !!!
 
(quoted from post at 18:50:06 06/07/23)
(quoted from post at 18:17:12 06/07/23) weak spark would cause the fouling of my plugs?
Click to expand...
Could be. I would also expect a weak spark to miss-fire under load and you haven't said anything about that. If you were able to fully thread in a 3/4" long plug, that is the CORRECT length because if it was too long it would smash the electrode !!!
Click to expand...
I took out the short plugs and put some seafoam in the cylinders and let it sit for about 30 min. I cranked over the engine without the plugs a couple times and then put in the AC Delco R45 xls's - 3/4". I fired it up and after some white smoking it seemed to run better. I ran it for about 45 min with a sickle mower, and it was fine for the first part and then I noticed that it started to lose power under load (going up hill, when I came to thicker grass). Under load I wasn't able to get any rpm's to increase power, even when I opened the throttle, and I did try to adjust the main jet, even opening it most of the way.
It never died on me, but I felt it was going to as it lost power so I came back from the field and checked the plugs. They were all black again, but had not yet caused the engine to die. I think the black smoke from the exhaust was a lot less though, maybe even gone entirely. The heat range on these plugs is 5 - DanielW suggested going up on the heat range to help burn off more deposits? Does it sound like I'm dealing with the problem that 13fx said where the carb is letting in too much fuel?
 
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