Stumped 8n won't start

Dave F.

Member
Son ran tractor out of gas put fresh gas back in tractor won't start, got tractor back in garage,
Checked for spark seems to have good blue spark at the plugs, took compression test. (#1cyl. 120lb) (#2-120lb.) (#3-110lb.) (#4-120lb.) So I think I have good compression. Took drain plug out of bottom of carburetor checked for fuel flow had good stream of gas out of carb. Cleaned plugs Tried starting tractor again just not firing. This tractor has a front distributor could it jumped time? has me stumped. Thanks Dave F.
 
Spray starting fluid into the air cleaner intake. If it starts then you know it's fuel problem and not ignition.

Also be sure that it is not flooded. Pull the tube off the intake of the carburetor and see if lots of gas runs out. If it does it is likely flooded.

Don't work on the tractor in a garage if fuel flooding is suspected. Might burn stuff down.

Zane
 
Haven't had a chance to see if spark will jump a 1/4" gap will try this sometime today. Thanks Dave F.
 
haven't checked the point voltage, Finally got the tractor started (by the way the spark would jump 1/4 inch.) Shut tractor off
& tried to restart it, But won't start so tomorrow I am going to get new points, condenser, rotor, cap & plugs hopefully this will
fix the starting problem. Thanks for all of the help. Dave F.
 
Well, got around to pulling the distributor turning the rotor shaft seemed tight to me. No side play in bearings but real tight. Other distributors I've worked on aren't tight spin freely, Is this normal for front distributors? just seems to tight something not right. Dave F
 
" No side play in bearings"

No bearings in it. Bushing. Distributor probably has little use or new bushings. Don't worry about it.

Have you got the new points, etc, installed?

Assuming that the bushings & advance weights are ok (*see below), & that you have correct voltage to the coil (battery voltage with the points open and about half that with the points closed), the problem is in the distributor.

The most common electrical failure (no spark, weak spark) points on the front mount are:

1. The insulator under the brass concave head screw & where the copper strip attaches. (it?s fiber & will wear out; poke & prod w/ your meter leads to make sure it still works) If you need to replace the insulator, use a .250 x 3/8 nylon square nylon anchor nut available at most big box home stores

2. The pigtail at the bottom of the coil not making contact w/ the concave head brass screw inside the distributor. (With the coil on, the pigtail must firmly contact the brass screw. No contact = no spark

3. The copper strip is broken or grounded to the plate. (look very carefully for cracks & breaks).

4. The condenser wire grounding to the plate or side of the distributor.

5. The tab on the bottom of the coil not making contact w/ the brass button on the cap. (With the cap on, the tab must firmly contact the brass button. No contact = no spark.)

6. Incorrect positioning of the spring clip on the plate causing the pigtail to ground. (the open part of the clip goes between 7 & 9 o?clock on the plate. That puts the straight part of the clip opposite of the timing screw at 3 o?clock)

7. Incorrect seating of the coil on the distributor due to a loose bail or no gasket.(the coil must not move at all; if it does, replace the gasket or bail. Or stick some cardboard under the bail).

8. Water/moisture inside the cap due to gasket failure or the absence of a gasket. (the cap AND coil have gaskets)

9. Dirty/corroded/burned/incorrectly gapped or misaligned points. I use only Wells, Blue Streak or Echlin brand points (* *see below). If you are using quality points and cannot get the gap to open to .015, chances are you need to replace the bushings.

10. Burned rotor, cracked/carbon tracked cap.

After you find the problem & re-check the point gap, do a continuity check before you put the distributor back on the tractor. Before you start, make sure your meter/light works.

With the distributor still off the tractor, follow these steps:

1. Coil off, cap off, points open. One probe on the brass screw & the other on both sides of the open points. On the side closest to the cam, you should have continuity. Not on the other side! If you do, you will also have continuity everywhere because the points are grounded.

2. Coil off, cap off, points open. One probe on the brass screw & the other anywhere on the body of the distributor. You should have no continuity! Now, rotate the tang on the distributor....as the points open & close, you have continuity (closed) and lose it when they open.

3. Put the coil on the distributor, cap off, points open. One probe on the lead on the top of the coil, the other on the cam side of the open points. You should have continuity!

4. Coil on, cap off, points open. One probe on the lead on the top of the coil, the other anywhere on the body of the distributor. You should have no continuity!

At this point, I just put the distributor, coil & cap all back on the tractor as a unit. The reason I do this is because it is real easy to get the cap or coil misaligned trying to put it back together, one piece at a time. The result is something gets broken or you get a ?no spark? problem.

It's possible to put it back on wrong & break it. Look at the slot on the end of the cam shaft. Whatever angle it happens to be, turn the distributor tang to match it. Make sure you can tell the wide side from the narrow side on both the cam & distributor! (close counts). Place the distributor on the front of the engine, gently push it in place & slowly turn the distributor body until you feel the tang slip into the slot. Rotate the distributor body until the bolt holes line up. Hand tighten the two bolts until the distributor body is flush with the timing gear cover.


* Unscrew the plate hold down screw & remove the C clip to get the plate out. Remove the shaft & weights. The weights should freely move.


* *NAPA part numbers:

? Points: FD-6769X
? Condenser: FD-71
? Rotor: FD-104
? Cap: FD-126
75 Tips
 

Bruce, thanks for the detailed troubleshooting procedures on the front-mount distributor.

I'm starting my own version of your "75 Tips," for personal use, grouped into categories, and based on some of the suggestions I'm gathering on this list.

Been doing this for years on other technical writing projects and software documentation.

Methinks there's an opportunity for a book in there somewhere, particularly since there are gaping holes in the I&T FO-4 manual, the 8N Dealer Service Training Manual, and (arghhh!) the Operator's Manual. Way too many assumptions and liberties are taken with the material.
 
(quoted from post at 12:23:12 09/19/16)
Bruce, thanks for the detailed troubleshooting procedures on the front-mount distributor.

I'm starting my own version of your "75 Tips," for personal use, grouped into categories, and based on some of the suggestions I'm gathering on this list.

Been doing this for years on other technical writing projects and software documentation.

Methinks there's an opportunity for a book in there somewhere, particularly since there are gaping holes in the I&T FO-4 manual, the 8N Dealer Service Training Manual, and (arghhh!) the Operator's Manual. Way too many assumptions and liberties are taken with the material.
Right? That list has saved me plenty of time.
 
Bruce (VA) I've pretty much done what you recommended, The tractor will start & run for about a minute & half & then just quit. No spark. Tried another coil started up ran about a minute & half & just quit running. No spark Can't believe I have 2 bad coils, Stumped again Dave F.
 
" Can't believe I have 2 bad coils, "

You do not have a bad coil.

" I've pretty much done what you recommended,"

Do it again.

As soon as it stops, make 100% certain that you have battery voltage to the coil.

If you do, the problem is in the distributor.

Go through the check list item by item & concentrate on things that are heat & vibration related. Like items 2, 5 & 6. The tractor has spark, then loses it.

Do the continuity check.

Lastly, replace the condenser.

Post back w/ results.
75 Tips
 

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