[tomb8764]

I need some help figuring out my problem(s) with my '48 8n. When I parked before the winter it ran great, as normal. Went to fire it up a few months back, and it wouldn't start. I started with the cheap stuff that it was due for anyway, points, condenser, cap, and rotor. I have the front mount distributor, so I pulled the whole unit out to rebuild. Put it all back together, still no spark at the plugs. I knew my coil was weak, as the summer before when it heated up I lost spark, so a bought a new one. I was in business now, got good spark and am running. But the tractor runs like garbage at high rpms. I know I know, check the firing order. Checked it 10 times 1243. So I though maybe I have a fouled plug, so I buy new plugs and copper core wires and reinstall them in the proper order of 1243. Still runs fine at an idle, but not good at all at high rpms. I've added heet to the tank to get the water removed(not sure if there even was any). On the advice of others I put some Marvel Mystery Oil in the cylinders and gas on the though that maybe I have a stuck valve, still nothing. As soon as I can I am going to check my compression. I have even cleaned the carb and put a new sediment bowl on the darn thing. I feel like I'm going crazy, nothing I or anything anybody has suggested has worked. Any help would be great.

Thanks

Tom

 

[bikerdave]

Have you checked the "advance mechanism" in the dist? Sometimes they stick and either won't idle or won't run at top of RPM range. Depends on where it stuck.

 

[tomb8764]

I will look into that. Idles like a champ, try revving it up and you would think you had the choke full on.

Thanks

 

[Lovesthedrive]

Did you replace the gas? Todays gas has more methanol in it.

 

[tomb8764]

The tank was empty as I just put a new sediment bowl/fuel shut off valve on. I was advised to add heet or a similar product to the tank with fresh gas to remove any water that may have been in the fuel lines or from condensation from the tank being empty. So yes, I did replace the gas.

 

[soundguy]

if spark is good, and if getting good gas, and if fire order is correct, and IF the small amount of timing adjustment you have, is correct, then DO check the advance mechanism. right now.. could be any of 10 things. very incorrect timing ( hard on a front mount ), or non working advance could cause the good idle, bad throttle condition.

when throttline and running bad, tug choke.. help any?

post back

 

[tomb8764]

As soon as I get motivated this morning I will look at the distributor to make sure the advance isn't the problem. And I tried messing with the choke while it was running and it just acted like it should with the choke on. When it does what it does it smells like it is burning really rich, maybe this is a piece of the puzzle? Not sure. Thanks for all the help so far. Sounds like I have some things to check today.

Tom

 

[Lovesthedrive]

the only thing a bad advance will do to you is when you gun the engine (unless the springs are gone, with cap off, gently twist the rotor one way or the other, you should encounter a spring load, if no load the rotor will not snap back, it will just wiggle back and forth). The advance changes timing on the gun or heavy on off on torque requirements. A flat out with slow rpm increase will bypass need for advance mechanism.

The only other item you want to look for is what looks like white scale on the insides of your carb. The older methanols would leave corn starch on the insides of the carb and make it run ragged.

 

[WyattB]

My first thoughts are point gap and rotation versus firing order. These tractors will run on two, operate fairly well on three but need four to run smooth. My money is on the gap but if you have the rotation of the rotor figured wrong then that would do it to.

 

[tomb8764]

I checked out the advance, it is just fine. And since I had the distributor on the bench I also reset the points just to be sure. Put it all back together, now I don't have spark again. Oh ya, I also have plenty of compression. So now I am back to tracking down where I am loosing spark. It's just a process of elimination, with everybody's help I'll get it eventually.

 

[Lovesthedrive]

Check the resistance across the coil. I think it is 1.14 if I remember correctly. If that checks out replace the condenser. Chevy condensers from 1968-1972 for the C-10 work very well.

 

[tomb8764]

I think I may have found part of my problem. When I realized I had no more spark, I had to take things back apart. I noticed my new coil had some defects, center of power stud on top missing, and two chunchs missing out of the back side. Thinkin' some happened to my coil, maybe causing my problems here. I don't know how long it has been this way, just noticed today. This coil has been on the tractor for less than a month, just bought it from Dennis Carpenter.
[attachment=0:3ocpqdxc]coil.jpg[/attachment:3ocpqdxc]

 

[soundguy]

make sure the insulated side of the points are not grounded out.. ie breake rplate damage .. etc..

 

[tomb8764]

all the guts of the distributer looked normal when I put it back together, but I will look again as I was able to overlook the coil being messed up.

 

[Lovesthedrive]

As I said before, check the resistance (with an ohmmeter) at the + and -, then + to the spark out put, and - to spark out put. If your reading is the same your golden. I think it is more likely your condenser as coils rarely ever go bad even with bits of bake light broken.

If you feel after the tractor still has probs. In a darkened area (dark of night is best). Start the tractor, with all the lights off, look at your wires and coil. If the shielding is bad, you will have quite the light show.

 

[soundguy]

Um.. it's been my experience that coils go bad WAY more often than condensors.

round coils? are pretty robust.. but the older dry ones can go bad... newer oil potted ones are better.

the square coils? they are junk.. even new ones are junk.. many are tar or epoxy potted.. neither are particularly good at getting rid of heat from a coil essentially mounted to the engine behind a hot water heat exchanger.

I have PLENTY of machines with original or vintage conditioners. I have only a couple original coils.

on a square coil, you have a top connection, and 2 bottom ones.. a pigtail and a flat tab.. tab is the secondary.. and should measure anywhere from 4-8k ohms tot he top post. the pig tail will likely measure anywhere from about .8 to 2.5 ohms, depending uon design, to the top post.


use an ohm meter to check breaker palte and condensor.

blindly replacing a condensor is a worthless waste of money and an poorly spent exercise of time and wrench work.

a vom will till you 95% of what you need to know on these old kettering ignition systems. an old analog one with a needle is actually, almst more usefull.. especially when checking condensors..

soundguy

 

[tomb8764]

Thanks soundguy, I am gonna have to go to the store to get a new 9v battery for my analog ohm meter. At the point I have no idea what the problem is. But checking the resistance on my electrical parts will shed some light on the issue. I am leaning towards the coil being bad, as it has some actual damage to it.Just for fun today I plan on wiring up a regular round coil to see if anything will work this way.

Thanks All

 

[Lovesthedrive]

If you dont have a coil, go to your autoparts and get a coil for a vw beetle, they were a true 12 volt coil.

 

[soundguy]

that ford frontmount coil is quite specialized in fit...

soundguy