8n has spark, no ignition

Johnny007

Member
I have rewired my 48(?) front dist. 8n, installed new points, gapped to 0.015, new voltage cutout, new ignition switch, new battery. Now she will turn over, all of the plugs are sparking, but I'm not getting ignition. I have fuel flow to the carb, steady as she drains when I pull the plug, new gas. What am I missing? Someone Please verify that my firing order is 1,2,4,3, and that the plugs are numbered 1-4, with 1 being closest to the radiator. Losing it here in VT!
 
Get yourself a spark tester. I got a Lisle 20610 Inline Spark Tester from Amazon for $13. Many others available out there. All the years of pulling off the wires and checking to see if spark is good or not are over. Just plug this inline. Learned my lesson by getting nailed by the spark on my Evinrude 99.9. Ouch.
 
Yes sir, 1-2-4-3, [b:7a71ff9978]CCW[/b:7a71ff9978], with #1 on the cap at the top left, about
10 o'clock, of the cap when looking at it from the front of the tractor.
Cylinders numbered 1 through 4 from the radiator back.
Its easy to swap 3 and 4 on the cap, but it still should start.

Now when you say all are sparking, blue/white spark?
Orange/yellow color would indicate weak spark.
I like the adjustable gap spark testers too.

Voltage cutout? Do you mean voltage regulator or do
you have an older 6V generator setup on it?
Not that the charging system really matters as to starting,
but you said you rewired it. 6V or 12V? That could matter.
What coil and resistors are you using?
 
It is a voltage cutout, and it does have a 6V generator setup with only the one wire coming off the Genny. I do not have a spark tester, guess I need to get one. Looking at the spark that get from each plug...I suppose they could be considered anemic, but it's pretty subjective to say without a tester, no?
6V, currently wired NEGATIVE ground. Would changing that to POSITIVE ground give me a better spark? Besides the connections at the battery, what other wiring changes would be needed? Using the original coil, resistor, and ammeter. The ammeter should also be replaced as I don't think it works. I also don't have a compression tester.
Finally, I am noticing that my #3 lead back to the distributor seems short...it's hard to reach the bottom right hand side of the distributor (#4 location...correct? The #4 lead goes into the upper right or #3 location on the distributor. The distributor is also labeled, which was a nice touch). I think these are the original leads, I wonder if they should also get replaced? Maybe I am getting resistance thru them? Thanks everyone for your time, it's frustrating on this end, but at least it turns over now....
 
" Looking at the spark that get from each plug...I suppose they could be considered anemic, but it's pretty subjective to say without a tester, no?"

It takes about 17kv to jump a 3/16" gap & 22kv to jump 1/4" in the open air, so that's why you need to use an old spark plug with the gap opened to 1/4". Or, a store bought plug checker which is more accurate & easier to use. Because it's 14psi outside of the engine & about 90psi at a 6:1 compression ratio in the cylinders & compressed air creates electrical resistance, you need the 17-22kv to fire the plugs when the engine is running.

" Would changing that to POSITIVE ground give me a better spark? "

No. But if you want to change it, reverse the battery connections & polarize the generator BEFORE you start it. (tip # 23)

" I think these are the original leads, I wonder if they should also get replaced? "
Yes.
75 Tips
 
Bruce, please elaborate on the benefits of switching from NEGATIVE ground to POSITIVE ground. I will grab a spark tester in the new future, and probably some new plug leads. Thanks for the advice, will advise
 
Well I went out and bought an inline spark tester, hooked it up this morning and the tractor starter right up, one crank! I shut it down, took off the tester, started right up again. Then I went out for a few hours with a smile on my face, came back, no start. I checked ally connections again, all tight and corrosion free. Tried to start it, and it started right up. Well hell, I said. I let her run for 20 minutes, idled strong, so I went ahead and drove it out in the field for some brush hogging. Mowed for about two hours, then she started sputtering, and ultimately died. No spark. I let her cool down overnight, this morning no spark. I guess I'll pull off the distributor (again) and make sure my points haven't shifted. New plug leads on order, should arrive next week. I wish my fields would stop growing so damn fast...
 
(quoted from post at 04:11:35 07/04/15) Mowed for about two hours, then she started sputtering, and ultimately died. No spark.

Possibly a bad key switch, even though it is new.
I would check for voltage at the distributor when you are getting no spark. A test light would suffice here. Some digital volt meters don't like the copper plug wires
 
(quoted from post at 04:26:16 07/02/15) Finally, I am noticing that my #3 lead back to the distributor seems short...it's hard to reach the bottom right hand side of the distributor (#4 location...correct? The #4 lead goes into the upper right or #3 location on the distributor. The distributor is also labeled, which was a nice touch).

Huh? The #3 lead is from the #3 plug? It should go into the #3 terminal on the distributor. Same for the #4 lead.

Visualize what happens as the distributor turns -- the rotor passes in order 1, 2, 4, 3 (the numbers molded into the cap) to give you the 1243 firing order. If you swap the leads like you say above, you have a firing order of 1234, which is wrong.
 
Well I went back out into the field this morning with my volt meter to check my connections again. I have 6.3 V at the battery, the key switch (on/off), the ignition switch, across the voltage cutout, voltage cutout "hot" side, and at the coil.

I also checked my connections at the ammeter, and small buss which takes connections from the cutout, ignition switch, and ammeter. Didn't find any connections too awful bad, and even ran my brass bristle over them to give them a little shine.
Still just turns over with no spark.

I must have read the numbers wrong on the front of the distributor, it is wired 1243 correctly. Brain cramp. New plug wires arrive this week. Maybe I'll pick up some new plugs as well. Anyone think I should try putting the old condenser in for grins? If so, why would it run for a couple hours and then just quit? Very frustrating.
 
I have resolved the "no spark" issue. Inside the distributor, the points spring and the brass screw that holds down the condenser wire have to be connected by a brass strap, or other conductive metal piece. There wasn't one in my distributor. Maybe it got burned up? I fashioned one out of stained glass copper tape, pretty flimsy, but when I hit the starter she started right up and I was able to get her back to the driveway at least.

Unfortunately, the wiring between the terminal buss and ammeter, and terminal buss and battery-side starter switch both melted, causing a giant "whoof" of smoke as the plastic melted, and immediate shutdown of the tractor. I'll be looking into why that happened, and re-wiring things again.
 
why would it run for a couple hours and then just quit? Very frustrating.[/quote]

My tractor would run for a while then quit when it needed a coil. Once the coil would get hot it would not work properly.

Also, I've had a couple vehicles with bad grounds. That tried to ground through other means....and those other "means" melted.

Just a thought.
 

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