9N misses badly at all rpm.

Volfandt

Member
I posted this on another forum:
SIL purchased this non-running 9N. It wouldn't even turn over.
This 9N is proving to be a huge test of my wrenching abilities, or lack there of.
Seems everything I do to it improves it for a time, then it reverts back to missing, back firing and lacking power.
To recap, the following is new:
points
condenser
rotor
dist cap
6v coil (with new home made rubber gasket)
plugs
plug wires
fuel bowl/cutoff
fuel line
floats tested - good
needle valve and seat
adjustable main jet adjuster (original was broken off)
(replaced carb with new after market brand)
starter push button
new ign toggle switch
solenoid
rewired OEM resister
added additional resister
battery.
rewired ign circuit
rewired and corrected 3 wire GM alternator (it charges)
Added isolation diode to alternator to prevent constant drain and run-on after key switch is turned off.
Topped off fuel tank with new clean gas

The plug wires were the last item I added.
Before I added them, the engine was running pretty good at all rpm and I was able to adjust it down to around 450 rpm for idle. It would start easily and I drove it all over my place.
Governor seemed to react slow but would increase/decrease rpm depending upon load.
After a combined hr or so of running over the course of a couple days it started missing badly and wouldn't run WOT. Pulling the choke would kill it so it didn't act like a fuel problem. atleast not a lack of fuel.
Double checked float setting (1/4" from lowest float point to carb housing with gasket in place) and double checked to make sure fuel wasn't flooding (it wasn't).
Pulled dist, rechecked gap (0.015), found advance flyweights froze closed, cleaned and freed them up. Set timing to 1/4" from mounting hole with straight edge. Put it back together and it ran great for awhile then started missing again.
Thinking the miss-matched plug wires may be bad I swapped them. No change in missing, backfiring and no WOT.
Engine misses badly, at times actin like it's only hitting on 2 or 3 cylinders and every now and then it will smooth out like it's hitting on all cyls.
Going to pull dist again tomorrow and double check everything again.
Since it did run great I'm not thinking burnt valves but haven't ruled out sticking valves.
Have to study up on checking that with as little disassembly as possible.

I did pull the dist again and nothing jumped out at me as being wrong. The points seem to open/close properly and conduct when close and don;t conduct when open,
The shaft doesn't seem to have any side play but the whole top bracket that holds the bushing seems somewhat flimsey but I don't know if it's normal or not.
Threw a new aftermarket carb to it, no change.
I'll be doing a compression test this weekend but somehow still think it's either ign or fuel related.

What am I overlooking?
 
Firing order is from front to back is 1243. Make sure the numbers on the distributor cap coincides with the firing order.
 
You say the engine ran well before you replaced the wires?
You need to ohm each wire for resistance. All wires should read the same ohms. If not,you just found your problem.
Is your tractor converted to 12 VDC? If so,is there a resistor or restive wire going to the points from the 12 VDC source.
If not the points will overheat and the plastic cam follower will melt causing a bad misfiring as the timing wanders..
Have you done a compression test?
Is there water in the fuel tank?
 
Thanks for all the replys.
The engine ran good after I got spark to the plugs but only for a short while then started missing badly.
I replaced the plug wires and it once again ran good for a while then started missing again. The firing order is right.
Thinking it was a fuel issue my SIL purchased a new aftermarket carb. Once again it ran good for a while then started missing.
Now the misssing stays and I can't smooth it out via the main adjuster. I can get it to idle somewhat smoothly for a short while. The idle adj's is out 1 turn, the main adj is turned out 1.5 turns.
Before we swapped the carb it seemed that letting it sit for a day or so would improve it for a short while, so we though fuel/carb issue
Fuel flow from the tank is a steady flow but not gushing.
When the engine starts to miss I can pull out the choke and it starts to stall so I don't think it's fuel starved, but then again it doesn't seem to follow any normal convention as far as just about any other engine I've troubleshot.

It was upgraded to 12v at some point but the alternator wasn't wired correctly (I corrected it) and the original ign resister wasn't wired up. Research indicated it should have a 2nd resister so we added an additional resister from TSC to the original resister in series to the coil terminal.. I've even wired around both resisters trying to isolate the problem. Shunting one or both produced no change.

This tractor wasn't running, had a dead battery and a fuel bowl fuil of crud. So we started replacing everything that either looked bad or didn't work.
 
Each time you have made a change and it runs good for a while, has everything been cold when you first start it after the change, and has it been warmed up each time it starts missing? Try letting the tractor sit for a day without making any changes to see if it runs good when cold and only has problems after it warms up.
 
sounds like your coil is breaking down when it get hot I put a 12 volt coil on a 2N that was changed to 12 volts and a one wire altenator
 
What are the ohms for the spark plug wires? What is the voltage going to the coil as read by a meter?
Start the engine and unplug one wire at a time at the spark plug ( don't be standing on wet ground) and see if you find one or more cylinder(s) where it makes no difference in the engine smoothness.
Rev the engine and turn it off. Pull the plugs and look at the plugs electrodes. Are any wet? Any fouled.
Remove all the plugs. Hook one plug on each wire up. Ground the plug and have some one turn over the engine. You should see a bright white/blue spark. If any plugs are throwing an orange spark you just found a problem.
Bad wire
plug
coil
condenser
Too low voltage going to the coil.
Just because parts are new,do think they are good. Too many times over my 56 years working on engines have I bought bad new parts.
If you do not have a meter your wasting your time. Harbor Freight tools have them for free with a coupon.
 
Ohm out the condenser. Use the Diode scale ( arrow and line looking sign) and place one lead on the wire the other on the case, the meter should show a voltage increase as the capacitor charges. Reversing the leads it should drop to zero volts almost instantly. If no rise in voltage the condenser is bad.
Did you check the points for the plastic follower melting?
 
(quoted from post at 18:07:13 10/05/16) Ohm out the condenser. Use the Diode scale ( arrow and line looking sign) and place one lead on the wire the other on the case, the meter should show a voltage increase as the capacitor charges.

What exactly does this mean? "Ohm out" does not have an exact definition in electricity/electronics that I am aware of, but when I've heard it used in the past it has meant to measure the resistance in ohms, but you talk about using the diode scale, not the ohms scale, and that the meter should show a voltage increase, but if you are "ohming out" the condensor, where are you seeing the voltage measurement? And if you are using the diode scale you are not "ohming out" anything.
 
'Round here "ohm out" is a verb implying the use of a DVOM no matter what actual measurement you're making with it. I know its not correct but aint gonna be the one to rock the boat.....
 
By Ohming out the condenser you will be doing two things,
1. you will charge the condenser with the meters battery. You will be able to see if the condenser will charge and then discharge when the leads are reversed.
2. You will be able to see is there is a short in the condenser by reading Ohms (resistance) or the lack of Ohms in the condenser housing or to electrical ground.
The same test will show if you have a bad spark plug wire,connector,plug itself,cap and rotor.
This simple test will save you time and effort in what is wrong,causing a misfire in the ignition system.
Once proven one way or the other,you can move on to the fuel delivery system or the mechanical components of the engine.
 
(quoted from post at 22:59:29 10/09/16) By Ohming out the condenser you will be doing two things,
1. you will charge the condenser with the meters battery. You will be able to see if the condenser will charge and then discharge when the leads are reversed.
2. You will be able to see is there is a short in the condenser by reading Ohms (resistance) or the lack of Ohms in the condenser housing or to electrical ground.
The same test will show if you have a bad spark plug wire,connector,plug itself,cap and rotor.
This simple test will save you time and effort in what is wrong,causing a misfire in the ignition system.
Once proven one way or the other,you can move on to the fuel delivery system or the mechanical components of the engine.

Are you saying that you use the meter twice on two different scale settings? If not, how can you measure both voltage to "see if the condenser will charge and then discharge" and resistance "by reading Ohms (resistance) or the lack of Ohms" ohms with one reading?
 
As the capacitor ( condenser) is charging on the Diode scale you will see the batter voltage start to increase. I used the term ohms for both test. I should have been more clear.
 

Thought I'd update. Pulled the hood so we can get a better look at everything. Nothing bad jumped out at us.
Compression test results:
Cyl 1 - 95 psi
Cyl 2 - 90 psi
Cyl 3 - 90 psi
Cyl 4 - 89 psi

They are all close so I don't suspect anything wrong there. I'm unsure if 90 psi is good or bad on these old flatheads but I suspect it is. Since they were all close I only did the dry test.

The plugs were sooty but not shiny so they aren't oil fouling out.

We're thinking of pulling the dist and letting this old timer check it out. I'm no spring chicken either so I respect the been there done thats, LOL
 
Compression reads normal.
I'd suspect the ignition or fuel( not so much)
A worn distributor can be way off on timing or not advancing in a normal way.
Being an old phart myself, I have a wealth of knowledge, if I can remember where I put it.
 

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