8N won't start

I'm going to apologize in advance to those who think this subject has been covered many times. I have searched the files and it seems like I have even more questions. Your help will be greatly appreciated.
I have a '49 8N, all as original, never restored, but very tired. This past spring I was unable to start it and I finally gave up until now when I am back on it. My other mower just died and so I need this badly.
There is plenty of gas at the carb. I replaced the 6v battery, the plugs (437s), points and condenser and it still would not fire. I was able to see spark when I held the wires away from the plugs but I did not know about the 1/4" test and I didn't save the old plugs so I have not done that yet. I can say that the spark was strong on two but not so strong on the other two.
Today I lifted the leads and cleaned the terminals at the ignition switch and at the resistor and then took some voltage measurements.
With the lead to the coil disconnected at the coil and the ignition switch on, I got 6.45v every place I measured it - at the battery, the two ignition SW terminals, at the terminals before and after the resistor, and at the end of the disconnected wire at the coil.
With the wire connected to the coil and the ignition switch on, I took the same measurements. The battery read 6.45 but both of the terminals on the ignition switch read 5.79v. The input to the resistor read 5.78v but the output lead from the resistor read 2.21v. At the terminal on the coil I measured 2.12v.
From what I had read on the searched posts, I concluded that the points must be closed so I jogged the engine with the starter four times and each time I measured the voltage at the coil. Twice I got 6.40v at the coil and I got 2.14 and 2.16 at the coil the other two times.
I was surprised that it seems like the points were open 2 times and closed 2 times.
Am I interpreting these readings correctly?
The other question I have: "Is the 2.14v at the coil with the points closed what I should be seeing there?
My next move is going to be to remove the distributor to see if I did anything wrong when I did that work this past spring.
One other thing - the spark plug wires are old. I have a new replacement kit but never installed it because I couldn't see how I was going to get the wires through the pipe without removing it and the head nuts where the pipe is mounted look like they have been there forever.
Thanks in advance for all comments and suggestions.

"The other question I have: "Is the 2.14v at the coil with the points closed what I should be seeing there?"

Yes. It seems your points are opening and closing correctly. Get a spark checker and confirm that the spark will jump 1/4".

"There is plenty of gas at the carb"

OK but is there gas in carb bowl? Remove the drain plug at the bottom of the carb to check for fuel flow thru the carb/

" I have a new replacement kit but never installed it because I couldn't see how I was going to get the wires through the pipe without removing it"

You do not need to remove the conduit.

Your life will be a lot easier if you totally rewire the tractor.

Push a coat hanger w/ a string attached through the conduit. Then, push one plug wire at a time. Lastly, tape the sting to the coil/generator wires & pull them through the conduit. Use a little dish soap.

Meanwhile....

Zip tie the new wires to the conduit as a temporary fix.

" My next move is going to be to remove the distributor to see if I did anything wrong when I did that work this past spring."

That would be an excellent move.

Assuming that the bushings & advance weights are ok (*see below), & that you have correct voltage to the coil (battery voltage with the points open and about half that with the points closed), the most common electrical failure (no spark, weak spark) points on the front mount are:

1. The insulator under the brass concave head screw & where the copper strip attaches. (it’s fiber & will wear out; poke & prod w/ your meter leads to make sure it still works) If you need to replace the insulator, use a .250 x 3/8 nylon square nylon anchor nut available at most big box home stores

2. The pigtail at the bottom of the coil not making contact w/ the concave head brass screw inside the distributor. (With the coil on, the pigtail must firmly contact the brass screw. No contact = no spark

3. The copper strip is broken or grounded to the plate. (look very carefully for cracks & breaks).

4. The condenser wire grounding to the plate or side of the distributor.

5. The tab on the bottom of the coil not making contact w/ the brass button on the cap. (With the cap on, the tab must firmly contact the brass button. No contact = no spark.)

6. Incorrect positioning of the spring clip on the plate causing the pigtail to ground. (the open part of the clip goes between 7 & 9 o’clock on the plate. That puts the straight part of the clip opposite of the timing screw at 3 o’clock)

7. Incorrect seating of the coil on the distributor due to a loose bail or no gasket.(the coil must not move at all; if it does, replace the gasket or bail. Or stick some cardboard under the bail).

8. Water/moisture inside the cap due to gasket failure or the absence of a gasket. (the cap AND coil have gaskets)

9. Dirty/corroded/burned/incorrectly gapped or misaligned points. I use only Wells, Blue Streak or Echlin brand points (* *see below). If you are using quality points and cannot get the gap to open to .015, chances are you need to replace the bushings. If the shaft has any sideways movement AT ALL, the bushings must be replaced.

10. Burned rotor, cracked/carbon tracked cap.

After find the problem & re-check the point gap, do a continuity check before you put the distributor back on the tractor. Before you start, make sure your meter/light works.

With the distributor still off the tractor, follow these steps:

1. Coil off, cap off, points open. One probe on the brass screw & the other on both sides of the open points. On the side closest to the cam, you should have continuity. Not on the other side! If you do, you will also have continuity everywhere because the points are grounded.

2. Coil off, cap off, points open. One probe on the brass screw & the other anywhere on the body of the distributor. You should have no continuity! Now, rotate the tang on the distributor....as the points open & close, you have continuity (closed) and lose it when they open.

3. Put the coil on the distributor, cap off, points open. One probe on the lead on the top of the coil, the other on the cam side of the open points. You should have continuity!

4. Coil on, cap off, points open. One probe on the lead on the top of the coil, the other anywhere on the body of the distributor. You should have no continuity!

At this point, I just put the distributor, coil & cap all back on the tractor as a unit. The reason I do this is because it is real easy to get the cap or coil misaligned trying to put it back together, one piece at a time. The result is something gets broken or you get a ‘no spark’ problem.

It's possible to put it back on wrong & break it. Look at the slot on the end of the cam shaft. Whatever angle it happens to be, turn the distributor tang to match it. Make sure you can tell the wide side from the narrow side on both the cam & distributor! (close counts). Place the distributor on the front of the engine, gently push it in place & slowly turn the distributor body until you feel the tang slip into the slot. Rotate the distributor body until the bolt holes line up. Hand tighten the two bolts until the distributor body is flush with the timing gear cover.

* Unscrew the plate hold down screw & remove the C clip to get the plate out. Remove the shaft & weights. The weights should freely move.

* *NAPA part numbers:

• Points: FD-6769X
• Condenser: FD-71
• Rotor: FD-104
• Cap: FD-126
75 Tips

When I replaced the wires on my 9n. I removed the spark
plug boots and taped the new wire to the old one.
Carefully pulled out the old wire in till the end of the
new wire came out of the tube. Then I put the boots on the
new wire and repeated the process three more times.

Thank you all for the helpful suggestions. I have just a couple more questions based upon your replies:
Since my voltage at the coil with the points closed is just 2/3 what it should be (2.16v vs 3.16v), is that enough of a discrepancy to say that needs to be addressed before all else? Do resistor coils fail by increasing resistance? This one looks like is has been there for many years, but the coil is not rusted. The posts at the ends could be however. Should I be trying to find a new one? Does NAPA carry these?
Would 2.16v versus 3.16v at the coil cause a weak spark?
Thanks for the NAPA part numbers. I'll see if they have a spark checker.
I did check the fuel by removing the carb bowl plug.

If you have fuel thru the carb and if you have spark and still no start, I would do a quick and dirty compression test. See if the
compression will blow you thumb off each hole when you turn the engine over.

" Since my voltage at the coil with the points closed is just 2/3 what it should be (2.16v vs 3.16v), is that enough of a discrepancy to say that needs to be addressed before all else? "

No. This is like horse shoes & hand grenades: close counts.

" Do resistor coils fail by increasing resistance?"

Yes...........but they rarely fail cold.


" Should I be trying to find a new one?"

No

" Does NAPA carry these?"

Probably; AZ does & so does this site.

" Would 2.16v versus 3.16v at the coil cause a weak spark?"

Theoretically yes. Realistically, no.

Bottom line: Nothing you have presented so far indicates a coil problem. There are at least 10 other things, all in the distributor, that I'd check before even thinking about the coil. Check those things out, buy an adjustable gap spark checker & see if you have a spark that will jump 1/4".

Post back w/ results or more questions.
75 Tips

your load test reveals voltage drops.

6.45 at battery ok.

5.78 at switch, not good...

should be bat volts all the way to one side of the resistor, and a lower number, probably 3-4v from there to the coil.

you have bad wiring or switch before the resistor most likely. 2.12 at the coil is super marginal / failure

" 5.78 at switch, not good.."

Yep.

My bad.

Missed that.

Need more coffee.

just a single point in a list of issues.

Today I removed the distributor and performed the list of checks suggested. I started with the continuity checks before I did any disassembly. I found that the concave brass screw was grounded to the case. When I removed the points the ground was gone, but I could not find anything wrong with the points (No ground path). I finally concluded that the ground existed only when the small screw holding the points to the insulated block was installed. When the screw was not installed and the points were removed, I could not find any grounds.
I have a spare distributor and since the points, condenser, rotor, and cap are all new (installed last Spring without solving the problem) I installed all of those in the other distributor and then performed all the checks and found no issues.
Then I did a check of the ignition switch as it was pointed out there should not have been a voltage drop across it. My ohmmeter registered some resistance through the switch - I don't know how much. My plan is to order a new one as soon as possible.
I didn't pull the plugs to perform a quick compression test, but last spring I did remove the inspection covers and verified there are no stuck valves.
Then I installed the distributor, hooked up the old spark plug wires and tried to start it.
It did not start but now it is trying to start - firing weakly.
I held the spark plug wires close to the plugs and got good spark at two plugs - at least 1/4" away (could hear the zap) and a bit less at the other two. I plan to find and order a plug checker. In the meantime I am going to change out the spark plug wires.
With a new ignition switch and new ignition wires my spark should not be an issue.
When it was trying to start, the only way I could get it to do that was to hold the choke out. I flooded it badly. Last spring when I was trying to start it I removed the carb and cleaned it thinking that was the problem. However, I had no knowledge of how to set it up again (needle valve setting, etc). My next step is going to be to find some instructions on that subject and repeat the look at the carb.
Thanks again for everyone's help.

" My plan is to order a new one as soon as possible."

Good idea. For a test & short-time solution, just jump the switch.

" When it was trying to start, the only way I could get it to do that was to hold the choke out. I flooded it badly. "

First, replace the plugs. You flooded it, they're fouled & it will be it next to impossible to start. You don't need to toss them; heat the tips for a few seconds w/ a propane torch to burn off the invisible spark-robbing deposits from today's additive filled gasoline........or wash them in lacquer thinner.

The usual cause of gas dripping out of the carb throat is operator error.
While each N has its own starting sequence, none of them will start well by just yanking out the choke rod & holding it out for 5 or 10 seconds while the engine cranks. This is a gravity fuel system on a low compression engine; it is easily flooded by too much choke.

Try this:

Key on, gas on 2 full turns, clutch in, 3/4 throttle, press the starter button. Let it crank for at least 3 - 4 seconds before you pull the choke rod. Then, don't hold it out for more than 2 or 3 seconds.

If you find out it will not start w/o excessive choking, you have problems.

Means you've been having problems, get a can of starting fluid. Once you resolve the spark problem, try starting it on starting fluid sprayed directly into the carb throat.

" I had no knowledge of how to set it up again (needle valve setting, etc)."

Both Ford and Marvel/Schebler (assuming you have a M/S carb ) say to set both the side-pointing idlemix and the down-pointing mainjet to 1-turn as a starting point. I set the down-pointing mainjet to 1-1/2 turns and don't fool w/ it until the final step.

Make sure the tractor is at operating temp; that usually takes 10 – 15 minutes at idle depending on ambient temp.

Then adjust the side-pointing idlemix for fastest idle; not the smoothest idle. Next, adjust the behind the carb idle-speed set-screw for very slow 400-rpms idle. Do that idlemix adjust for maximum idle at least 3-times. Make sure that you turn the screws slowly, like 1/8 of a turn at a time & wait a second or two for the engine to catch up. Take your time!

Do it like this:

1. Adjust idle mix jet until RPM increases

2. Adjust idle-mix set screw until the engine nearly stops (as slow as you can get it unless you have a tach that tells you 400 rpm)

Repeat steps 1 - 3 three times.

Remember the side-pointing idlemix is out for lean, in for rich.

If you do not have any problems inside the carb, it is easy to get the idle down to 350 - 400 rpms.

Your last step is to go back to the main jet. Remember, in for lean, out for rich. If you end up turning it OUT more than ½ turn for max power (remember, you already had it 1 ½ turns out) then stop right there because you have a dirty carb or a fuel problem.
75 Tips

I think I'm making progress, but still no start.
I replaced the ignition switch and now I have zero voltage drop across the switch. However, I still have only about 2.1v at the coil which is the same as the output post of the resistor.
I also did the quick and dirty check of compression and got good blowout of each cylinder.
I replaced all of the ignition wires and bought an adjustable spark tester. I am now getting a good zap at each cylinder across the 1/4" gap.
I also washed the plug tips with lacquer thinner.
After that I tried to start it. It was pretty much the same as the previous attempt. It was trying to fire, or was firing weakly, but did not start. It did better when I pulled the choke, but again did not start and gas was dripping out of the air intake of the carb.
The carb (M/S) is now apart and soaking in carburetor cleaner.
I have not tried to remove any of the valve seats as I am afraid I will not be successful and I don't have a rebuild kit anyway. I plan to blow air through the passages after I take them out of the cleaner.
I wasn't sure, but I think possibly one of the holes at the bottom of the bowl might have been plugged.

(quoted from post at 18:22:33 08/29/15) I think I'm making progress, but still no start.
I replaced the ignition switch and now I have zero voltage drop across the switch. However, I still have only about 2.1v at the coil which is the same as the output post of the resistor.
I also did the quick and dirty check of compression and got good blowout of each cylinder.
I replaced all of the ignition wires and bought an adjustable spark tester. I am now getting a good zap at each cylinder across the 1/4" gap.
I also washed the plug tips with lacquer thinner.
After that I tried to start it. It was pretty much the same as the previous attempt. It was trying to fire, or was firing weakly, but did not start. It did better when I pulled the choke, but again did not start and gas was dripping out of the air intake of the carb.
The carb (M/S) is now apart and soaking in carburetor cleaner.
I have not tried to remove any of the valve seats as I am afraid I will not be successful and I don't have a rebuild kit anyway. I plan to blow air through the passages after I take them out of the cleaner.
I wasn't sure, but I think possibly one of the holes at the bottom of the bowl might have been plugged.

Click to expand...

If you keep flooding it, you will never get it to start. Clean the plugs again and get a can of starting fluid. And keep your hand off the choke.

When I fouled my plugs, I cleaned them all on a wire wheel until they were bright and shiney. I do not know if this is "best practices" - but it worked. Anyone have an opinion about cleaning fouled plugs on a wire wheel? Since no one suggested it, it's probably a bad idea... but I do not know why.

My father had a gas station and had a pneumatic sand blaster that cleaned the plugs. It was attached to his work bench and the sand went into a little bag. I see you can buy those things at harbor freight for $15.

" Anyone have an opinion about cleaning fouled plugs on a wire wheel?"

Yes.

It's not a good idea because you leave metal deposits on the center electrode which will serve as a conductor.

Sand blasting is the best way.

But......the specific topic here is gas fouling, not carbon or oil. Spraying them off w/ brake cleaner, acetone, etc will work just fine.
75 Tips

I reassembled the carb after soaking and cleaning (I was able to remove the needle valve seats) and reinstalled it. I then tried to start it and did not touch the choke. It would not fire at all. I then squirted starting fluid into the carb intake and got some weak firing but still no start.
I used the spark tester to verify I still have the 1/4" spark and it is strong as before.
I guess the next step is to measure the compression but I can't get my tester into the spark plug holes. I'm guessing there is a right angle fitting I can get so that it my next step. Any other ideas?

Try pull starting it. Key on, 5mph, 3rd or 4th gear, ease the clutch out slowly.

You can increase compression sufficiently by pulling it to start for two reasons. First, it's cranking faster which creates more compression & secondly all of the battery current is going to the ignition & not the starter. Sometimes you get the same result by jumping it w/ a 12v battery. (see tip # 43 for the safe way to do that)

A compression test is easy to do & will answer a number of questions about your problem.

First, take a look at the picture. ( and tip # 46)

If your gauge has a fitting that screws into the spark plug hole & the hose from the gauge screws into the fitting, do yourself a favor & get a brass elbow at the hardware store. Screw the fitting from the compression gauge into the head, the brass elbow into that, & the gauge into the elbow. Makes it easier to fit under the gas tank. (hint: take the gauge & fitting w/ you to the hardware store!)

Minimum acceptable pressure is 90 lbs w/ the lowest pressure reading w/in 75% of the highest reading. Run the engine to operating temp, turn it off, remove all 4 plugs, remove the breather hose & make sure the choke and throttle are both open. Crank it at least 5 compression strokes or until the gauge stops moving. Write down the first compression reading (that is the valves seating) then write down the reading after 5 strokes or when it stops increasing. You should have two numbers for each cylinder. Then, add a tablespoon of oil to each cylinder & repeat the process, but you only need the final reading for each cylinder. Write down the results & post back for help figuring out what it all means.

All that being said........

The fact that you have a 1/4" spark & it won't fire on starting fluid tells me you have a dirty/mis-adjusted carb.

75 Tips

Following up on what I said below re the carb.........

There are 6 things critical to a successful carb rebuild:

1. RTFM. Read The Freakin Manual....in this case, this link:
http://ytforums.ytmag.com/viewtopic.php?p=2810328&highlight=#2810328. If you don’t rebuild a lot of carbs, lay out each piece you remove on a clean shop towel so that you don’t lose the little screws/jets, etc.

2. Get the very caustic cleaner that comes w/ a wire basket from your local auto store & follow the directions.

3. Use a wire, welding rod tip or whatever it takes to clean every single passage. Be careful w/ the wire; you do not want to bore out the passages. If you do not have a set of gunsmith screwdrivers to remove the jets, be very, very careful. (this is an excuse to get a set)Or just leave them alone.

4. Blow out every passage w/ compressed air (this is an excuse to buy a compressor, BTW)

5. Make sure both halves mate; use a straight edge.

6. Make sure the throttle bushing are ok before you start because most kits do not come w/ them. If you need throttle bushings, replace them or the tractor will never idle due to air leaking.

If you are uncomfortable doing a rebuild, take it to a local rebuild shop. If you do not have a local rebuild shop, give these guys a call for a quote & shipping info:

Automotive Manufacturers Inc
2400 N Lombardy St Richmond, VA 23220

(804) 321-6861

They do mail order work. They rebuild carbs, clutches, pressure plates, water pumps, alternators, generators, starters & reline brakes.
75 Tips

Tries to start but choke floods it out,
may sound silly but do you have fresh gas in the old girl?

The gas is about 9 months old now, but last spring it was only 4-5 months old when it first failed to start. Replacing it sounds like a good idea.
My compression tester does not have the removable fitting at the end of the hose. I have looked for an elbow on the internet but have not found anything yet. Maybe I can find a straight fitting and then buy an elbow to fit into that.
I also have a spare carburetor. I have it all apart now and soaking. I need a rebuild kit for this one but when I went on the YT site to buy one, I found they have two kits for MS carburetors. What is the difference between the two MS carbs and how do I know which kit to order?
When I cleaned the carb on the tractor now I did blow it out with compressed air and I did run wire through the passages.

" The gas is about 9 months old now,"

Drain it, add at least 2 gallons of fresh gas. But still rely on no choke & starter fluid.

" Maybe I can find a straight fitting and then buy an elbow to fit into that."

You'll probably have better luck finding a new gauge.

" What is the difference between the two MS carbs and how do I know which kit to order?"

The kits are different because they are for different carbs. Which carb do you have? Is it a TSX33, Ford 9N9510A or a TSX241A, TSX241B, & TSX241C, Ford 8N9510C?

Six months ago after the previous post, I used a kit to clean and rebuild the carburetor but still had no success. At this time I was getting the spark to jumps a 1/4" gap in my tester after replacing the ignition switch, spark plug wires and plugs, points, condenser, and cap but with no improvement. I walked away from it for the rest of the year and did all the mowing with a smaller mower and the bush hogging was never done. At Christmas time with family here I asked them to help me push the 8N from the machine shed into my work shop where I could work on it under better conditions. This week I got back on it and rechecked all my work from last year. I drained the gas and put new in. I also replaced the resistor in the ignition circuit because my voltage at the coil was about 1v lower than what is expected. Still no start.
So today I removed the spark plugs and put about a tablespoon of oil into each cylinder, turned it over a few times, reinstalled the spark plugs and it started immediately on the first attempt!
The one suggestion I never followed up on was to buy a new compression gauge with a removable fitting at the end so I could install an elbow in order to install the gauge. I guess my thinking was that knowing what the compression is won't solve anything and I already knew it was low because of the age of the tractor and the fact that the engine has not been overhauled.
It would, however, have led me to the problem sooner so in hind sight I should have done that.
I guess what happened a year ago was that while sitting over the winter, any oil on the rings and cylinder walls had drained down and compression was lost to the point where it would not start. My plan now is to run it often and possibly find an additive for the oil or gas to increase the compression.
Thank you to everyone, especially Bruce, for your help and suggestions.