Rebuilt 8N won't start

reluskie

Member
I just finished rebuilding a tired 8N motor. The engine ran before I started the project but was in dire need of repair (really sloppy pistons and burning lots of oil). I replaced the bearings, sleeves and pistons and also converted the motor from the 6 volt system to 12 volts. My future son-in-law even put a fresh coat of paint on the entire tractor.
I'm getting good spark and the fuel is flowing from the tank to the carb but it will not fire. I took the manifold off and bumped the starter to make sure all the valves were operating properly, all were moving up and down and not sticking. I have 3 sets of plugs and have even tried putting the original set back int to get it to fire. Before we installed the distributor we made sure the valves were closed like they are supposed to be, the timing should be OK but don't have a real good way of determining if it's 180 degrees off. My next step will be to rotate the distributor cap to see if that does anything but we have attempted that one other time and it didn't do anything.
It seems to be a fuel problem so I put a few drops of fuel in each piston and then tried to start it up. I got a few pops but nothing more than that, it will turn over but will not fire. I disconnected the air filter breather tube and put my hand over the carb and it feels like it is trying to suck air into the carb. I am absolutely baffled, the old girl looks better than she has in years but now won't fire up. Any suggestions?
thanks
Ray
 
An engine needs 3 things to run:
1)Fuel/air mixture
2)Spark - at the right time
3)Compression.

I suggest first checking compression with a gauge. If it is over 100 psi, this should confirm that the valve timing is OK - at least enough to run. Without proper compression, the engine will not start.

Next, bring #1 up on compression, and check that the distributor rotor is pointing to the #1 wire on the cap. This should indicate whether the distributor is in correctly or 180 degrees off.

If this all checks out, that would leave a fuel problem. Carb float level? Needle and seat blocked/stuck? Enough fuel coming from fuel pump?

Once the above 3 conditions are satisfied, the engine will start. Your challenge is to figure out which one is causing the problem.
 
you pulled the plug on the bottom of the carb and
after the bowl drained the fuel kept flowing
right?

you set the fuel mixture(front screw) out 1.5
turns from seated and the side air mixture screw
around 1/2 turn from seated right? your firing
order is correct right? I believe it is 1243.
double check everything. check compression. I did
one years age where one of the sleeves were up a
little holding the head from making a good seal,
compression check will tell you a lot. not much
too these things check check and double check
 
Fuel pump???????????????? A 8N is a gravity flow fuel system and has no fuel pump and very few older tractors had fuel pumps
 
Bring No1 piston near the radiator to TDC on the compression stroke. Your rotor should be pointing to your No1 plug tower which looks to be in the 11 o'clock area. Also your plug wires need to go in this firing order to the correct sparkplug.
1-2 As the rotor rotates CW. Hal
3-4
a134399.jpg
 
Grandfather was 50+ year veteran of overhauls. Others will disagree but he did dozens of these and claims to NEVER had an overhauled one start on the battery. Give her a pull. May start right up.
 
Thanks for the tips. I found a suggestion on line for checking to see if the spark was sufficient. I used a 3/16" gap on a spark plug and it did jump the big gap but the color was yellow/orange. I did have good fuel flow when the plug was pulled from the bottom of the carb. I have an extra coil and putting a new set of points/condenser in it tomorrow. I'll walk through all the "double check" suggestions and see if I can get to the bottom of the problem. I'll update WHEN I get it started.
thanks
Ray
 
Double check your distributor to make sure it's timed to No1 piston as it could be time to No4
piston and then your plug wires are installed wrong. Hal
 
hey one other thing with the 12v conversion. did you install a resistor and have you tried jumping it
 
We did install the resistor but when you refer to "jumping it" I assume just by pass the resistor. I have not tried that but I still have the original 6 volt coil. Will bypassing the resistor screw that up?
We dragged the tractor up and down the road today and still couldn't get it to fire up. We're rounding up a compression tester to make sure we do have good compression on all the cylinders.
One other thing we noticed. While we were trying to "pull" start it the motor seemed like it wanted to start but just wouldn't fire. The 3rd and 4th outlets on the manifold block were hot like it was running but the first cylinder was cold, we could touch it without any pain - not the case on the 3rd or 4th.
 
I purchased a new distributor cap tonight and will put in on tomorrow. We plan to "Start over" on the distributor alignment and wiring. It certainly is acting like a timing issue.
 
I remember dad having a heck of a time getting the 8N to start after the rebuild.

Sounds like you need to recheck the spark to each cylinder. You aren't getting fire at the right time to the cold cylinders. If you have the hood off it will be pretty easy to determine firing for timing. Hope the cam/distributor isn't off.

I had an engine that I jacked up like that. I just kept rotating the plug wires around the cap until I hit on the magic combo. I always look at that and it makes me crazy but it runs like a top.
 
Are you sure you have the distributor timed to No1
piston when its at tdc on the compression stroke?
Remove the sparkplug near the radiator and bring that piston to tdc on the compression stroke then take a look and see where the rotor is pointing. Hal
 
Did you pull the crankshaft and camshaft during the engine rebuild? If you did you may not have the cam in time with the crankshaft gear. I would pull that front cover and take a look. Hal
 
Here are the cam and crankshaft gears on a 9N Ford tractor in time. Your 8N should be similar. Hal
a134631.jpg
 
(quoted from post at 14:18:06 11/04/13) Bring No1 piston near the radiator to TDC on the compression stroke. Your rotor should be pointing to your No1 plug tower which looks to be in the 11 o'clock area. Also your plug wires need to go in this firing order to the correct sparkplug.
1-2 As the rotor rotates CW. Hal
3-4
a134399.jpg
ooks like a mag to me. Sure not an 8N distributor. 8N distributor rotates CCW, NOT CW. If he wasn't confused before, he ought to be by now! :roll:
 
You said that you put a few drops of fuel into the cylinders and that it DID pop a few times. If that is true and by "pop" you meant it fired then you have a fuel problem. It may not be whether you have enough fuel but the quality of the fuel in the tank. Where did you get the fuel to squirt in the cylinders that you said fired?? Take some good fresh fuel and squirt it into the air inlet of carb while rolling over and see what happens before you go wasting a lot of time.Even at 180 off you should get some banging. Bad gas or bad condenser is my guess. Let us know.
 
I think you are on the right track. The gas came from a can I just filled but there was a little in the tank before I added more. We dragged it around the yard and all 4 ports on the exhaust manifold were hot. Almost thought it was going to start when the throttle was held wide open. I wish I had another carburetor to swap.
 
Was the cam and crankshaft removed during the rebuild? Your valve timing may be off if they're not in time. Hal
 
Sounds like a spark timing issue to me. Don't rotate the cap, install the distributor correctly. If you are absolutely certain the timing gears are installed correctly, then rotate the engine to #1 TDC and see where the rotor is pointing in the distributer. Since you rebuilt the engine, I assume you have a service manual.
On the fuel issue. Did you pull the plug on the bottom of the carb to verify fuel at the carb or just see fuel coming out of the fuel line? There is a difference. I just rebuilt a card on a Massey Ferguson and the new needle stuck in the shut off position. Hope this helps. Gerard
You certainly received some interesting replies.
 
It would be helpful to know if he has a front-mount or a side mount distributor, as the front one can ONLY be installed correctly (without bending or breaking things), and it's cap is clearly marked as to which cylinder each terminal needs to lead to.
 
We confirmed the timing and even pulled the distributor and started the process all over. It must be a fuel issue, I think I'll buy a new carb at it, I've spent a ton of money on this pig, might was well throw another $120 at it!
 
We did not rebuild the lifters and did not remove any of those parts. The crankshaft was removed and turned but nothing else.
 
I did pull the plug on the bottom of the carb and filled a soda bottle about 1/2 way before shutting it off.
 
You still need to time the crankshaft gear with
the cam gear. Your distributor will also be out of time.
 
If you installed the crankshaft and didn't time it with the cam gear as shown in the upper picture
it will never start. Your valve timing will be off and so will the ignition. You could pull the timing gear cover and rotate the engine to see your timing marks. They should be aligned as shown in the picture. You don't need a new carburetor to get it to run. Hal
a135235.jpg
 

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