strange ignition behavior- what could this indicate?

drtym30 · Jun 28, 2017

hey everyone, wanted to ask for some advice here. i've never seen anything like this before:

my '52 N all of a sudden went from running perfectly well, to missing under load, idle, & all throttle settings. after double checking everything from fuel to point gap, i found that unplugging the coil wire from the coil & holding it about 2mm above the coil contact while running (so blue sparks are visible) solves the issue. fully seating the coil wire causes the miss to come back.

what does this mean? seems like the extra gap the spark travels from coil to wire fixes the miss/ rough running. i'm stumped here. i've swapped in a new coil, same issue. new coil wire, new cap, condenser and plugs give same result. checked and rechecked point gap @ .025 all 4 lobes. as soon as the coil wire is seated fully into the coil, it returns to running rough. running blue streak/ standard ignition components. 12v, 3 wire alt. zenith carb. sidemount dist. AL437's at .025

what is going on here? appreciate the input and all the past help i've received by searching this forum.

Dell (WA) · Jun 29, 2017

drtym30.......yer beginning description of running well to missing under load sounds like WATER in the fuel. Changing sparkies (AutoLite 437's gapped 0.025) was the 1st correct step. Notta fan of zenith carbie. As a general rule, unlike the 4-nipple frontmount, the 5-nipple sidemount coil is bullet-proof. Why fully seating the coil wire makes the miss come back, dunno. Maybe you gott some of that STRING sparkie wire fer yer BelchFire-V8 computer conrolled junk........HTH, Dell, yer self-appointed sparkie-meister

drtym30 · Jun 29, 2017

thanks dell, your replies & advice to other threads have guided me well in the past. running solid tinned copper core wires.

yes that zenith (previous owner's doing) is very particular, though i've had it running great up until now.

swapped all 6gallons remaining to fresh ethanol free fuel two days ago when issue began, took out the plug in the bottom of the carb, and drained it that way, to make sure float isn't stuck. was certain it was a fuel issue. my local station carries booze free gas that i've been running in my implements for a year or so now.

i'm going to throw another set of blue streak breakers in and gap em to .025 and report back. maybe my points are out of wack? i've opened and closed the gap from .020 up to .035 just to see what's up. didn't help at all.

why would holding the coil wire above the coil alleviate the issue? it was running so well, but this is just odd....will report back after work tonight. looks like that extra "gap" the spark travels fixes whatever is going on.

i'm missing something here....

Ncorrigible · Jun 29, 2017

There were thingys that essentially added gap to the spark plugs that caused a stronger hotter spark - just like you did. I
would go with Bruce (VA) and make darned sure that the spark jumps a 1/4 inch air gap. A cheap check that will tell you a
bunch.

teddy52food · Jun 29, 2017

Your plugs are fouled. Put in new ones.

Tim PloughNman Daley RIP · Jun 29, 2017

yeah, sounds like a lack of fuel or bad fuel problem. How did you check for fuel flow? Missing could be bad wiring or loose sparkplug wire or spark plug wire not in correct order. Start over with fuel issue then proceed to electrical...I concur, not a fan of the Zenith carbs either, nor 12-volt convulsions...especially with a 3-wire alternator...

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drtym30 · Jun 29, 2017

that's what i initially thought. tank is fairly new from P.O.

checked for fuel/ drained the tank through bottom of carb to check for stuck float and strong fuel flow. steady stream all the way to the reserve, strong flow when reserve open as well.

i'll throw in my other set of 437's tonight, these have been torched/ wire brushed a few times to clear the fouling from the plugs on the missing cylinders since this issue began. maybe cleaning them isn't enough. they may be toast.

i'm not convinced the zenith is an "upgrade" and may be sourcing a marvel carb here soon. (although i have the finicky zenith tune procedure down pat finally.) i hate that main adjustment "T"

will report back tonight after i swap the plugs again.

Ncorrigible is right, the stronger spark from increased gap is fixing whatever is going on here. just gotta figure out why all of a sudden the normal spark gap isn't enough after all this time of running perfectly.... thanks everyone

JMOR · Jun 29, 2017

(quoted from post at 09:12:55 06/29/17) yeah, sounds like a lack of fuel or bad fuel problem. How did you check for fuel flow? Missing could be bad wiring or loose sparkplug wire or spark plug wire not in correct order. Start over with fuel issue then proceed to electrical...I concur, not a fan of the Zenith carbs either, nor 12-volt convulsions...especially with a 3-wire alternator...

[i:5a10491cb7][b:5a10491cb7]<font size="4">Tim Daley(MI)</font>[/b:5a10491cb7][/i:5a10491cb7]<table width="100" border="1" cellpadding="0" cellspacing="0" bordercolor="#000000"><tr><td height="25" colspan="2" bgcolor="#CC0000"><center><font color="#FFFFFF" size="3">*9N653I* & *8NI55I3*</font></center></td></tr><tr><td><img src=http://img.photobucket.com/albums/a379/ploughNman/TPD9N100.jpg></td><td><img src=http://img.photobucket.com/albums/a379/ploughNman/TPD8N100.jpg></td></tr></table>

o ballast resistor, correct?

drtym30 · Jun 29, 2017

it does have a 4 terminal reisitor ( old, square, white) above the battery compartment. think this could be it? was running without issue for about 6 months since i've had the tractor. i know my old coil, and the one i just swapped with, are the internally resisted type....

JMOR · Jun 29, 2017

(quoted from post at 10:59:25 06/29/17)
it does have a 4 terminal reisitor ( old, square, white) above the battery compartment. think this could be it? was running without issue for about 6 months since i've had the tractor. i know my old coil, and the one i just swapped with, are the internally resisted type....

hat would be my number one suspect

drtym30 · Jun 29, 2017

didn't cross my mind until now. i'll bypass it tonight, or replace it? leaning towards getting it out of the ignition circuit? correct?

i guess that's just a leftover from the original 6v system?

good call, thanks man.

JMOR · Jun 29, 2017

(quoted from post at 11:22:20 06/29/17)
didn't cross my mind until now. i'll bypass it tonight, or replace it? leaning towards getting it out of the ignition circuit? correct?

i guess that's just a leftover from the original 6v system?

good call, thanks man.

ofires, indicating a weak coil/spark & over resisted is likely your cause.u said that you have a 12v coil requiring no external ballast, so get rid of resistor. JFYI, pulling the wire to add air gap allows coil voltage to rise higher before plug fires, meaning coil/spark was weak & over resisted coil circuit was likely your cause.

drtym30 · Jun 29, 2017

that's what i was looking for. thanks for the help.

the P.O. didn't really know what he was doing. (no guts in the air filter, no thermostat, a set of champion H-10 plugs gapped all the way to .40, and a firing order CCW 1234.

assuming they're the ones who slapped the zenith and 12v conversion and left the resistor in line.

i'll report back tonight after i chuck that resistor. thanks guys, fingers crossed

drtym30 · Jun 29, 2017

UPDATE:

Huge thanks to JMOR and everyone else. bypassed the leftover resister from the 6v system, and she's back to normal.

all those little gremlins and popping/ poor running i wrote off as carb, plug & points issues were coming from this **** reisitor.

looks like it took the hot Virginia weather to toast the resister enough to cause my issue after all this time.

YT forum comes through for me again.

thanks again! running better than ever.

p.s anyone want a zenith carb? ???? jk, have a good one everyone [/img]

JMOR · Jun 29, 2017

(quoted from post at 20:35:37 06/29/17) UPDATE:

Huge thanks to JMOR and everyone else. bypassed the leftover resister from the 6v system, and she's back to normal.

all those little gremlins and popping/ poor running i wrote off as carb, plug & points issues were coming from this **** reisitor.

looks like it took the hot Virginia weather to toast the resister enough to cause my issue after all this time.

YT forum comes through for me again.

thanks again! running better than ever.

p.s anyone want a zenith carb? ???? jk, have a good one everyone [/img]

lad it worked out for you & that all my years of experience & education were not lost!

drtym30 · Jun 29, 2017

for sure! thanks again for passing it on. you nailed it.

Hobo,NC · Jun 30, 2017

HELLO that's great... Thank the man he understands water in the fuel are like a lack of fuel or bad fuel problem had little to do with the info you provided... 8)

Plugs fouled maybe...

This is a good reason to buy a spark tester...

drtym30 · Jul 1, 2017

well said, Hobo. anyone else with this issue can surely benefit from the answers you guys had. & i learned what increasing the air gap in your ignition system is telling you. funny that resistor from the p.o hid in my system for so long....guess the hot weather did it in.....

strange ignition behavior- what could this indicate?

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