8n will start and idle fine but missfires at half throttle to full! PLEASE HELP

[Midniteoyl]

and do you have to hook to the wire leaving the coil that connects to the points? hard to do on a front mount.

Wouldnt be hard to do...

 

[rsallen]

Humm, it does look like it could be an interesting problem to solve.
Never seen anything quite like that kind of set up.

Perhaps sacrifice a cap and do a little filing or drilling to run a wire?
Or is a cap cost prohibitive?
It'd be nice to put to bed a lousy set of points or bad cam lobe.

 

[Egon]

If you check out other 8N threads on this site you'll find some good explanations and maybe some diagrams.

 

[Soundguy]

I would try a different condenser. Sometimes new ones are defective.

Do the points have a screw to hold the wires from the coil and condenser? If it just uses spring pressure it may not be making a reliable connection.

I've had vehicles run terrible or quit from both these problems.

condensors are easy to test with a ohm meter. or simple observation of the points AND use of an ohm meter.

a condensor that fils short will act like closed up points.

a condensor that fails open will allow the points to arc, pit and burn quickly.

some condensors self heal a bit in less heat... that's when you look at it hot then cold, and then observe the points. if, hot, and points shorted.. but cold not.. then you have a shorting condensor. if hot and cold no short.. but points are burning rapidly. and you are sure points are not dirty and do not have insuficient gap.. then suspect condensor opening.. etc.

 

[Soundguy]

Wouldnt be hard to do...

you'd have to have a good insulated flat wire to snake out from under the coil to dizzy mating connection.. and it can't be thick or it won't let the coil properly seat on the dizzy where the short pigtail has to ride inside the concave head screw.. and the flat metal tab of the secondary rid the lil bb shaped nub on the dizzy cap.

I never said not possibly... just not for the average guy tht hasn't worked on a front mount before.

Besides.. it's an exercise in futility.

you static adjust the timing of the dizzy with it off the tractor using a ruler anyway...

it only goes back on 1 way, and you are assured of it being correctly timed... no magic tricks needed.

 

[rsallen]

So you don't think a dwell reading/s would be worth while?
Shrug, no matter to me. IF, and it could be a big if, if everything in there is okay.
So it's back to a timing light to check the advance curve.......make sure the plug wires are solid core........then on to the carb system.

One step at a time.

 

[jinman]

The system I've used to find misses in engines due to arc-over is to put the vehicle inside a garage or barn in full darkness and then set the brake with the tractor in gear and load the engine by slowly releasing the clutch. When the engine misses, you often see a spark jumping right where there is a breakdown in insulation, moisture, or broken distributor caps. Another thing you can do is to put an AM radio tuned off station with the volume turned up. Set it near the engine and load the engine. If there is a spark jumping, the discharge will create RF and the radio will start popping every time a spark jumps.

 

[Soundguy]

it's just NOT a common test for THAT dizzy.

if you static time it correctly, and GAP the points correctly, AND the bushings are good, AND the advance is working correctly. it's pretty much DBO.. It's not like you can rotate it or anything....

 

[rsallen]

Oh, I definitely believe you when you say that it's not common to be running a dwell check on a set up like that.

Other than point gap though you're not looking at timing with a dwell reading, you're watching the operation and performance of the distributor relative to the points and visa versa.

 

[mbryant51375]

it's obvious here that some of the advice givers are 100% unfamiliar with the ford front mount coil and distribuitor. the coil mounts atop the distribuitor bottom to top. the outgoing primary and secondary connections are completely warded and unavailable without creative work..

First thnx to everyone who replied with suggestions! Now for the results, it ended up being the advance springs, which we was told by our parts supplier/tractor shop that the advance was fine! Being he has 40 yrs of experince and specializes in 8n/9n/2n tractors I took his word and went with it, also I absolutely refuse to just unnecessarily throw parts at anything. We will also replace bushings for good measure.

Conclusion is trust your instincts and go with what you know!

Again thnx for all the replys!