Why No Spark

I have a 3 cyl gas, mid 70s JD 1020. Started running rough and died. Can't get any fire out of distributor. Have tried:
-new/rebuilt distributor
-3 dif caps & rotor buttons
-2 dif 12v coils & 2 sets standard points
-2 dif electronic ing modules & high energy coils
-new plugs & reworked plug wires
Basically its new from dist to plugs.....STILL....no spark out of distributor.
-has battery voltage on + side of coil, 0.6 on - side with points, bat voltage with electronic module
-have battery voltage on center button in cap from coil wire
-can get bat voltage to tip of rotor button
-rotor button position appears correct to service manual specs @ TDC. Does not appear to have jumped time.
-dist IS turning
No spark...
-cleaned bat ground @ block, distributor base and fork. Continuity meters good ground.
-previously running with a new bat, alt & ing/charging system has been completely rewired.
Basically have checked, metered, or replaced all I know to. I am now begging for any suggestion or input...

I too have a 1020 gas. I'm guessing that the various testing is done statically. I do know the 1020 has a thermal cut-out behind the dash but can't say where it interrupts current flow. I had the insulator bushing for the hot wire into the starter fail such that engine vibration shorted and the thermal kicked in. Could it be that your voltage checks don't induce the vibration from normal operation?
Kinda out there but you describe a strange problem.

My tractor not equiped with what you describe, but thanks!

Remove the electronic ignition and install the original points an see if you have fire then. I have had several electronic modules fail. I know you say you changed modules but I still think you have an electronic issue. A points system is easier to diagnose. If you get fire then look at the trigger for the electronic module.

I originally thought it was the module and installed a new one. When that failed to fix the prob, I did install a new set of points...no help. I installed a complert new/rebuilt dist (2nd set)....still no. Thanks for the reply.

Take a analog volt meter and hook it to the battery side of the coil. Then crank the tractor over and see what the voltage does while cranking. A digital voltmeter will not respond to a voltage fluctuation as quick as a analog one will. You may have voltage under no load but not enough amperage while under load.

HERES A SLOW STEP BY STEP TROUBLESHOOTING PROCESS FOR YOU

SEE MY COMPLETE IGNITION TROUBLESHOOTING LINK BELOW


1) Very first thing, with Ignition ON there has to be voltage present on the high INPUT (NOT to distributor) side of the coil............That's true regardless if its points or an elec module.

2) If NOTTTTTTTTTTTTTTTTT see if it has a ballast resistance wire either on the back of the Ign switch itself, or in series between switch and coils high INPUT. NO FIRE UNTILL THERES VOLTAGE ON THE COILS SMALL HIGH INPUT TERMINAL WITH IGN SWITCH ON If NOT try a hot jump wire to coils high INPUT (NOT to distributor) terminal and see if it fires then????????????? That eliminates any Ign switch or ballast wire or ballast resistor problem. NOTE if it uses a ballast resistor wire on the switch itself or ballast resistor between switch and coil and its bad/open NO FIRE AS THERE MUST BE VOLTAGE TO THE COIL (via switch and any if so equipped ballast resistor wire or resistor) WITH IGN ON!!!!!!! Also if it uses a ballast resistor it may use a 6 instead of a 12 volt coil !!!!

3) Another sort of on tractor bench test, is to jump a hot wire to the coils small high input (NOT to dist) terminal to eliminate any switch or ballast problem,,,,,,,,,,,,,,REMOVE the wire from coils output to dist stud (to eliminate any inside dist problem),,,,,,,,,,,,,,use a jumper wire to momentarily attach then remove a circuit from coils output to frame ground,,,,,,,,,,,,,,,,,EACH TIME THE WIRE IS GROUNDED BUT THEN REMOVED, THE COIL SHOULD FIRE !!!!!!!!!!!!!!!

3) Once you have voltage on the coils small high input terminal (via switch and any on switch or series resistor wire or ballast) put a test lamp or meter on the coils other small OUTPUT to distributor terminal. It should be the same voltage as on the coils input when points are open, but zero volts when they are closed. If the engine was cranked slowly a test lamp on coils output to dist (or dist input stud) should flash ON (points open) and OFF (points closed) NO FIRE UNTIL THAT HAPPENS.

NOW FOR A MORE COMPLETE AND DETAILED METHOD AND REASONS FOR FIRE OR NO FIRE, CLICK ON THE URL LINK BELOW AND FOLLOW MY TROUBLESHOOTING PROCEDURE.

There MUST be voltage to the coils input with Ign on from switch and any if so equipped ballast wire or resistance,,,,,,,,,,,,,There MUST be voltage on the coils output to dist with points OPEN, but zero volts when closed

(A) If its always zero volts (no light) on coils output, the points are closed orrrrrrrrrrrr condenser is shorted orrrrrrrrrr the points or condenser wire or points themselves are shorted orrrrrrrrrrrrrrrrrrrrrrr the PASS THRU INSULATOR ON SIDE OF DIST IS SHORTED OUT TEST FOR THAT !!!!!!!!!!!!!!!!!

(B) If theres always voltage on coils output to dist terminal (should be volts when points open but none when closed), points aren't closing down full orrrrrrrrrrrrrr a wires bad/open from coil to dist pass thru then points orrrrrrrrrrrr dist or points arent well grounded.

DISCLAMIER I'm NOT a New Generation expert and not any 1020 man and not sure if it has the resistor wire on back of switch or resistor ballast wire from switch to coil !!!! REGARDLESS there MUST be voltage to the coils small input terminal with IGN ON or the switch is bad or ballast wire (if so equipped) is bad/open. SIMILAR the voltage on coils output or dist stud must flash ON and OFF as engine is rotated.

JOHN T'S IGNITION TROUBLESHOOTING http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=5745

John T
John Ts Ignition Troubleshooting

How are you checking the spark? At the plug or at the coil wire? Are
the points gaped properly? Is the wire going into the distributor from
the coil insulated from the housing properly?

You're throwing parts at the problem. You need to back up a bit.

You say it has an electronic ignition module, which you've replaced. But I doubt that is original; I think you tried replacing the original points with an electronic ignition. Generally speaking, it's not a good idea to make major changes when you're trying to troubleshoot a problem. The points-and-condensor system is pretty easy to troubleshoot; electronic aftermarket not so much.

I would go back to the original points, and work from there. With the points open, you should have 12 volts at the distributor side of the coil. With the points closed, you should have zero volts at the distributor side of the coil. Opening the closed points with a screwdriver should generate a spark from the coil. It's that simple.

How are you getting battery voltage on the rotor tip? That is the 2ndary. Spark comes from the coil, not from the dist.

bad switch

Yes , what ?

???????????????????? What are you asking???????????

So after giving up on it, I TOOK THE 2ND SET OF POINTS BACK OUT (someone said take the elecltronic module out and go back to standard points, which I posted in my original post had already been done .....twice), put the electronic module and high energy coil back in as I had it (system is 12 volt so no ballast resistor is needed as someone suggested). Run back thru the timing sequence per service manual and got it to fire ...an run poorly only @ idle with about 3/4 choke. Adjusted and restabbed dist twice advancing 1 tooth at a time. Did not change poor running significantly. The inital problem was no fire as posted in original message (someone wasnt able to figure that out). I also said I had battery voltage at the + side of the coil (so no its not the switch), and had already tried a bypass jumper. Throwing parts at the problem? Maybe, but was systematically woking the problem by process of elimination. At this point my best guess that for some reason it has jumped time and the next systematic thing to do is validate timing in the front end of the engine.

How the heck is that happening -- new one on me.

Sorry, but your "systematic process of elimination" has you changing stuff which you have no reason to believe is bad. While you're at it, replace those rusty lug nuts and that worn fan belt.

The more things you change, the more likely you are to create a new problem that didn't exist before you started trying to fix the original problem. You are correct that it's probably out of time, if only because you deliberately changed the timing.

On vehicles with timing chains, it's common for the chain to jump a tooth on a worn sprocket. But I think that tractor has timing gears, not a chain. It is possible, however, for a distributor or camshaft failure to cause timing to chain. I've seen it happen when the pin securing the distributor gear to the shaft sheared. Usually the distributor doesn't turn at all if that happens.

Running poorly with 3/4 choke doesn't sound like an ignition problem. Are the spark plugs wet? If they aren't (after all that choking), you're not getting enough fuel.

I don't mean to be harsh, but these are things I've learned the hard way from fixing a lot of different stuff.

If I held the rotor button up into the cap, I could get bat voltage to the button tip. Was trying to validate nothing wrong in the rotor.

Good Grief!!!!
The best advice you can get here is to print out John T's ignition troubleshooting procedure and FOLLOW IT!!!
As already stated, you are just throwing parts at it. Not one bit of diagnostic work has gone into it. So, I guess now that you have run out of parts to change, you expect a "short answer" that will solve the problem.

Now, I will add my thoughts. IF the engine is running at all, that would mean that you do have spark. Maybe not a good spark, but nevertheless a spark. That being the case, I would check for proper compression. If compression is low, it would indicate a problem with the timing gears. If you have good compression, that rules out timing gears. It does not rule out timing being off. To insure that the timing is close to correct, bring number 1 up on compression. Align the timing marks to TDC. At this point, the distributor rotor should point to the number 1 wire on the distributor cap. If not, you may have found your problem.
If you have spark and compression, this points to a fuel problem.

Bear in mind that those of us on this forum are not able to see, hear, and touch what is at your end, so you have to be our eyes, ears, and hands.

Well first, thanks for your reply. No I would not change lugs nuts or the belt as that doesn't pertain to the "no fire" issue. I am curious though about how you would have proceeded. The issue is no spark to the plugs, it has a elect module not points. You have the correct voltage at the coil and into the cap to the center button... And rotor tip if held inside the cap at the rotor tip. You said "put the original points back in", which I did, as posted. Didnt change the problem. What would be YOUR next step, please?

Rule number one when troubleshooting a problem: If what you see doesn't make sense, back up until you find something that DOES make sense. You would not be the first person to troubleshoot a "spark" issue only to find out that the spark is fine.

Unless you own an oscilloscope, you can't tell if you have the "correct" voltage on the distributor side of the coil primary winding, since you have an electronic pickup rather than points. I don't believe you can see the electronic pickup fire using a multimeter. But if you have mechanical points, you can easily check the voltage at the distributor side of the coil primary winding while opening the points with a screwdriver. 12 volts when the points are open, zero when they are closed. What did you see when you did this? That was the reason for changing back to points: so you can do this test.

You say you have the "correct" voltage into the cap at the distributor? Are you saying you're getting a spark when you pull the coil wire off the distributor and hold it near a ground while cranking? If so, then you DO have spark. If not, then the voltage there is not "correct". Whatever DC voltage you might read on the secondary coil terminal is irrelevant. One end of the coil secondary winding is tied to the primary winding. If you have 12 volts DC at both sides of the coil primary, you will necessarily have 12 volts DC on the secondary side of the coil; it doesn't mean anything.

At any rate, you now have it running, although poorly. So you MUST be getting a spark, even if it's a weak spark. The engine is probably not running on all cylinders. Pull the spark plugs and look at their condition. If any are wet, chances are those cylinders are not firing.

The pass thropugh from the coil to the points inside may be grounded. Put a test light on the the connection at the outside of the distributor. With it in Neutral and the brakes
on or wheels blocked, turn on the ignition and crank it. If the test light flashes the points are working, if not they are grounded or the condenser is shorted. Jim

I would hazard a guess that more electronic modules have been ruined with wiring errors than there are units in service .

Yep. Spark at the points, nothing at the plugs. Whats next?

> Yep. Spark at the points, nothing at the plugs. Whats next?

Uh, you said it was running, albeit poorly. Either it runs or there's no spark at the plugs. Which one is it?

As I said earlier, you would not be the first person to troubleshoot a "no spark" condition when in fact the ignition system is fine. I've done it myself more than once. Once again: If you're seeing something that makes no sense, BACK UP until you find something that DOES make sense.

Forget its running poorly for now. If you had spark @ the points but nothing @ the plugs, WHAT wouls YOU do next? And that was someone else that made the spark expert comment, not me.

> If you had spark @ the points but nothing @ the plugs, WHAT wouls YOU do next?

Troubleshooting is always the same: Start with something good and move forward until you find something bad, then go backwards and forwards until you're sure of where the problem is.

Assumptions: "spark @ the points" means you see an arc across the points when they open. "nothing @ the plugs" means you don't see an arc if you remove a spark plug, plug it back into its lead, ground it and crank the starter.

Go forward, then back. Pull the distributor end of the coil wire and see if you can get an arc from the coil wire to ground. If no, it's probably the coil. If yes, check the spark from one of the plug wires to ground. If that's bad, check the distributor cap and rotor.

Cap, rotor , coil all good. New in fact. Still spark @ points, nothing @ plugs or wire tip to ground. Whats next?

How about bring it to TDC and validate rotor position to #1 firing cyl via tje alignment pin in tje flywheel? Done! Fite @ points....nothing at plugs or wire tip to ground. What's next?

In all of my years running and tinkering with gas engines on tractors, cars, trucks, etc. I've had one condenser failure and it exhibited most of the symptoms that you described. In my case, I was mowing with a bush-hog when the old girl just died and wouldn't restart. I checked everything as usual in such cases and then the 'light' went on in my head: what IF, I thought and replaced the condenser. KA-BOOM, back in business! This may or may not be relevant to your tractor but I figured I'd throw it out there. Good luck to you!

THANK YOU! That is a reasonable suggestion. I did try a 2nd condenser...and points. No change. Thanks for considering the issue, I do appreciate suggestions.

HEY...TRACTOR DODO ...spark @ points, not to plugs, cap, rotor, coil, mechanical timing validated. Spark @ points, not @ plugs. WHAT IS NEXT?

TRACTOR (guru) DODO....My point. There is nothing to "back up to that makes sense". Sometimes "throwing parts at the problem" IS all you can do....which IS systematically working the problem. You would have realized I had already worked all your suggestions IF you would have read my original post carefully. Some folks like to throw out a bunch on innuendo, assumptions and accusations mask as "advise" when actually they are a forum/chat room TROLL! My first try at getting help this way, AND MY LAST. My last post until I resolve the issue and then I will advise what the cause/issue actually is/was. Going to check the valve train first for a stuck valve or broken spring, then the front end timing gears. Thank those who actually offered something intelligent and useful. Thanks...David....the BolivarRatman