9N has no power

DG55

New User
I have a recently acquired 9N that has me stumped. It seems to idle fine, but doesn't have enough power to move itself unless you choke it. All the ignition components
from the rotor to the plugs have been replaced and there is good spark at all 4 plugs. It has a new carb and fuel filter and there is plenty of gas flowing through the
carb. The intake manifold has been honed and tested for leaks. All 4 cylinders have compression at 90-100. It appears to be running only on cylinders 1 and 4. I can
remove the 2 and 3 spark plug wires and it runs the same. If I reverse the 2 and 3 spark plugs it backfires through the carb about once every 10 seconds. What should I
check next?
 
Firing order 1-2-4-3 [b:1f43b8a112]Counter[/b:1f43b8a112] clockwise on the distributor as viewed
from the front? #1 cylinder closest to the radiator, 2-3-4 to the rear.
After that I would ask for a definition of "good spark".
 
6 volt/positive ground or 12-volt with alternator? Firing order is as Royse said - 1,2,4,3 CCW -see picture. Check wiring, do a continuity test, don't just go by wire colors, they mean nothing and colors do not conduct electrons. Seek out Bruce(VA)'s 75 Tips For N-Owners and download a copy. Tips will tell how to check for spark.


Tbt5WvEl.jpg


Tim *PloughNman* Daley(MI)
 
6 volt or 12 volt?

Don?t guess at the cause of the problem; guessing can get expensive. And leave you breathless chasing every guess.......it could be this, it could be that......just troubleshoot the problem and leave the guess work for buying Lottery tickets.

Did you confirm that the advance weights were ok when you had the distributor off?

You need to answer 2 questions before you do anything else:

With the bolt in the carb bowl removed and the gas on, will the fuel flow fill a pint jar in less than 2 minutes?

Next, get out your adjustable gap spark checker * , open the gap to 1/4", hook it up, turn the key on and crank the engine. Does the spark jump 1/4"? Post back with the answers.

Next, confirm the firing order from the cap: 1-2-4-3, CCW

And do not buy a new part for the tractor until you can answer this question: how do I know the part on the tractor is defective?



* Don't own an adjustable gap spark checker? Buy one! Not a test light! Until then, take an old plug, open the gap 1/4" ground it to the head & look for spark. It?s not the color of the spark that counts; it?s the distance it jumps.
75 Tips
 
Thanks for the suggestions.

To address some of the points you made.

Fuel: There is plenty of fuel in the system. It runs nicely out of the bottom of carb.

Firing order: To test whether we had the 2 and 3 wires crossed, we intentionally reversed them and that caused it to backfire.

Spark: All of the ignition components from the condenser to the plugs have been replaced. In addition, we have tried different plugs in 2 and 3 and it made no difference.

So, for the sake of discussion, assume those things aren't the issue. What else could me causing the problem? My fear is that it is in the valve train and, on this old tractor, there is no adjustment on the tappets.
 
Your initial entry indicates [b:b2d8c3baca][i:b2d8c3baca]"All 4 cylinders have compression at 90-100"[/i:b2d8c3baca][/b:b2d8c3baca] which clears your sticky valves concerns.

I've heard that a skinny point setting will cause low power.

The reason it runs better with the choke applied is that a fatter A/F ratio is easier to ignite. Lean is more difficult.

A lean A/F mixture could be result of a vacuum leak on cylinders 2&3. Quick check would be to spray the intake around the suspected cylinders with starting fluid. If the RPM increase, you've diagnosed your problem. Likely a blown gasket.
 

Thanks for the comment. We suspected a vacuum leak as well and, as a result, we have removed the intake manifold, tested it for leaks, and reinstalled it with a new
gasket. It didn't help.

You mentioned a blown gasket. Is there another gasket, other than the intake manifold, that I should check?
 

DG55, you come here as a first time poster, asking for help. Your posts indicate a lot of knowledge and experience. You should answer Bruce (VA)'s questions if you really want help.

Fuel: There is plenty of fuel in the system. It runs nicely out of the bottom of carb.

Spark: All of the ignition components from the condenser to the plugs have been replaced. In addition, we have tried different plugs in 2 and 3 and it made no difference.

So, for the sake of discussion, assume those things aren't the issue. What else could me causing the problem? My fear is that it is in the valve train and, on this old tractor, there is no adjustment on the tappets.
 
(quoted from post at 05:40:55 11/16/17) Thanks for the suggestions.

To address some of the points you made.

Fuel: There is plenty of fuel in the system. It runs nicely out of the bottom of carb.

Firing order: To test whether we had the 2 and 3 wires crossed, we intentionally reversed them and that caused it to backfire.

Spark: All of the ignition components from the condenser to the plugs have been replaced. In addition, we have tried different plugs in 2 and 3 and it made no difference.

So, for the sake of discussion, assume those things aren't the issue. What else could me causing the problem? My fear is that it is in the valve train and, on this old tractor, there is no adjustment on the tappets.


Well, you can assume that all is well if you wish. I wouldn't and that is why I asked for specific information to assist you in your diagnostics. " runs nicely out of the bottom of the carb" does NOT tell you if you if the flow will fill a pint jar under 2 minutes. Likewise, all new parts does NOT mean they are not defective out of the box or that you installed them correctly. Does the spark jump 1/4" in open air or not? And have you inspected the advance weights or not?

You do NOT have a valve or compression . My advice is for you to check the obvious and so far it does not appear that you have.
 
Gentlemen, Please do not take my lack of response to specific suggestions as being dismissive or disrespectful in any way. The tractor is 300 miles away from me so I can't simply run out the door to the shop and do things. Believe, if I could have I would have. So given the reality of my situation, I looking for ideas and theories to test when I next have a chance to work on it which will likely be in 2 or 3 weeks.

With respect to the specific test of fuel flow. Last time I worked on the tractor I did remove the plug from the bottom of the carb and I am quite sure it would have past the pint in 2 minutes test. I know for certain it was a dramatic improvement from my previous test, the difference being I had replaced the inline fuel filter.

With respect to the specific test of the spark, I will certainly do that test next time. I like the simplicity of that test.

With respect to the advance weights, I have not inspected them, but I will.

I am also trying to apply some logic to the situation, given that I have already attempted to address common issues. One particular test I did stands out in my mind. I start the tractor and it seems to idle just fine. If I disconnect the spark plug wires on cylinders 2 and 3, there is no change in how it idles. If I disconnect either wires 1 or 4, the engine dies. That causes me to ask the question "what could cause a lack of combustion in cylinders 2 and 3?" Given that cylinders 1 and 4 appear to run fine, and the fuel flow test mentioned above, I don't think the issue is with fuel. Thinking I might have crossed the spark plug wires on 2 and 3, I reversed them which caused an occasional backfire through the carb. From that I conclude I had the spark plug wires on correct. When I installed new plugs, did I get a couple bad ones? I replaced both plugs and, again, no change. Next I wondered if it was sucking outside air into cylinders 2 and 3 instead of a fuel mixture. I sprayed starting fluid around the intake manifold and it made no difference. Pursuing the manifold possibility 1 step further, I removed it, cleaned it, tested it and reinstalled it with a new gasket. No change. Which leads me to say "I'm stumped". If I am asking the wrong question, please tell me.

Again, thanks for the suggestions and I will perform the 3 tests when I next get a chance. If anyone wants to suggest other things to check, I am all ears.
 
(quoted from post at 08:48:59 11/18/17) Gentlemen, Please do not take my lack of response to specific suggestions as being dismissive or disrespectful in any way. The tractor is 300 miles away from me so I can't simply run out the door to the shop and do things. Believe, if I could have I would have. So given the reality of my situation, I looking for ideas and theories to test when I next have a chance to work on it which will likely be in 2 or 3 weeks.

With respect to the specific test of fuel flow. Last time I worked on the tractor I did remove the plug from the bottom of the carb and I am quite sure it would have past the pint in 2 minutes test. I know for certain it was a dramatic improvement from my previous test, the difference being I had replaced the inline fuel filter.

With respect to the specific test of the spark, I will certainly do that test next time. I like the simplicity of that test.

With respect to the advance weights, I have not inspected them, but I will.

I am also trying to apply some logic to the situation, given that I have already attempted to address common issues. One particular test I did stands out in my mind. I start the tractor and it seems to idle just fine. If I disconnect the spark plug wires on cylinders 2 and 3, there is no change in how it idles. If I disconnect either wires 1 or 4, the engine dies. That causes me to ask the question "what could cause a lack of combustion in cylinders 2 and 3?" Given that cylinders 1 and 4 appear to run fine, and the fuel flow test mentioned above, I don't think the issue is with fuel. Thinking I might have crossed the spark plug wires on 2 and 3, I reversed them which caused an occasional backfire through the carb. From that I conclude I had the spark plug wires on correct. When I installed new plugs, did I get a couple bad ones? I replaced both plugs and, again, no change. Next I wondered if it was sucking outside air into cylinders 2 and 3 instead of a fuel mixture. I sprayed starting fluid around the intake manifold and it made no difference. Pursuing the manifold possibility 1 step further, I removed it, cleaned it, tested it and reinstalled it with a new gasket. No change. Which leads me to say "I'm stumped". If I am asking the wrong question, please tell me.

Again, thanks for the suggestions and I will perform the 3 tests when I next get a chance. If anyone wants to suggest other things to check, I am all ears.

There are easily a dozen things that could be the problem and the ideas you are suggesting are pretty much out of the realm of possibility. Not impossible, just not likely. So, stick with the simple stuff. Check spark to see if it jumps 1/4". Pull the distributor and check the advance weights. And check the point gap at .015 on all 4 lobes while you are in there. Take a can of starting fluid. If you suspect fouled plugs, take a can of brake cleaner. And if you suspect defective plugs or wires on 2&3, just exchange the plugs w/ 1&2. Use an ohmmeter on the wires. You can also use an ohmmeter to check the cap at 2&3. (and that's unlikely as well) Now back to the in-line fuel filter. If you have the wrong one, it will restrict fuel flow significantly. So do the fuel flow test again for the full 2 minutes. And once it's running, I'd replace the fuel line & get rid of the filter; see tip # 15.
 
1) The 9N is now running just fine.

2) Thank you, Bruce (VA), for pushing me hard to recheck the basics.

3) There were 2 problems with the fuel. One problem was an intermittent air lock in the line between the tank and the carb. That problem went away once we removed the in line filter. The other problem was the new carb we had installed. We knew there had to be a problem with the carb when we removed the fuel needle completely and it ran fine. We took it to the local carb expert and he said the ________ manufacturer had failed to drill one critical hole in the carb. He drilled out that hole and it ran perfectly. He said he sees this problem with some regularity.
 
(quoted from post at 14:53:39 12/02/17) 1) The 9N is now running just fine.

2) Thank you, Bruce (VA), for pushing me hard to recheck the basics.

3) There were 2 problems with the fuel. One problem was an intermittent air lock in the line between the tank and the carb. That problem went away once we removed the in line filter. The other problem was the new carb we had installed. We knew there had to be a problem with the carb when we removed the fuel needle completely and it ran fine. We took it to the local carb expert and he said the ________ manufacturer had failed to drill one critical hole in the carb. He drilled out that hole and it ran perfectly. He said he sees this problem with some regularity.

You're welcome. Glad to help. Thanks for the follow-up.
 

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