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8n no spark when hot

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Tim PloughNman Daley
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PostPosted: Tue Sep 10, 2019 2:40 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

It's the distributor. First thing is to verify the battery is at full charge and checks good under load. Simply charging the battery does not ensure that it is good. You need to know if it is a 6V Coil or a 12V coil first. Pull the distributor off and take the coil off the unit. Then take your VOM out, set to 'OHMS' scale, and put one probe (it doesn't matter which is which, checking static and the coil is not polarized anyway) to the Pigtail contact on the bottom and the other probe to the terminal stud on top. A 6V coil will read approx 1.3 OHMS and a 12V coil about double that. Once you verify your coil is 6V or 12V you can then proceed from there. If you have a 6V coil on the front mount, you will need to add an inline, ceramic 1 OHM resistor to the circuit. If you have a 12V coil, no extra resistor is needed. You say you have the correct Ballast Resistor for the front mount. Was there something wrong with the old one? Swapping out new parts for old willy nilly without knowing first if old ones are bad is a mistake often made by newbies and some oldies as well. Aftermarket parts mean nothing- they can vary one place to another. Get the OEM MPC for the correct part numbers to identify your supplier. I use a reliable supplier like just 8n's so there's no question. Next is to verify the wiring is correct -seek "WIRING PICTOGRAMS by JMOR". Why did you decide to completely rewire the tractor? Were they old and worn? Did the tractor run before you changed it? You relied on a kid who said he 'replaced the dizzy'. Mistake #2. If you or your kid doesn't know the correct way to mount the front distributor, you can easily get it 180? off location and the fist time it gets power it's burnt toast. Doing the proper tuneup/dizzy rebuild is a necessity. If you or your kid do not know the procedure, find someone who does. That means setting the points to .015" gap and setting the timing correctly. Then you test it before you mount it. So, moving on. Assuming the Ballast Resistor is correctly wired, distributor on. Measure the battery voltage static and remember or write it down. Take your VOM and set to DC Volts. Take a probe, again it doesn't matter which one, not a polarized test, and set it to the LH terminal post on Ballast Resistor looking at it from the back of dash. This is the one that feeds to the coil -that's all it does. next, turn key switch 'ON' but do not turn over the engine. Then place the other VOM probe to ground anywhere and you should be reading HALF you battery voltage reading you remembered to write down. If test passes, repeat only move the resistor terminal probe to the top of the coil post. You should have the same reading which means your ignition is getting power. If the test fails, you have something not wired correctly. Check the Ballast Resistor LH terminal to see if is the coil wire. Once coil test passes, and you still don't have spark, its safe to assume your distributor is mucked up. The points/timing/condenser/ are not set correctly or you mounted it wrong and you busted the distributor aluminum base at the offset cam unit. If the latter, your distributor is trash and needs replacing. I suggest to get an OEM unit and rebuild it rather than a buying a new aftermarket part. The tang on the distributor is offset and matched to the cam on the engine. If it isn't exactly matched and is 180? off, it won't set flush and will break the unit. Member Farmer Dan is an expert hand at rebuild the Ford distributors and has about half dozen front mounts correctly rebuilt and ready to go. His email: dansden@usa.com

FORD FRONT MOUNT DISTRIBUTOR BUSTED CAM & WEIGHT UNIT BASE FROM INCORRECT CAM TANG SETTING:


Tim *PloughNman* Daley(MI)
 
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J.Mc
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PostPosted: Tue Sep 10, 2019 7:34 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

JMOR or someone can most definitely correct me if I'm wrong, but I don't believe you have enough resistance in your circuit and its overheating your coil. I think you should be at about 4 amps for your coil. A 12v circuit isn't truly 12v. It's more around 14.5. Using ohms law with the information you've provided 14.5 (volts) 2.1 ( your total resistance) = 6.9 (amps). I think you may need another resistor to bring it down some.
Someone please correct me if I'm wrong. I dont claim to be a professional Shocked
 
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JMOR
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PostPosted: Tue Sep 10, 2019 7:51 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

J.Mc wrote:
(quoted from post at 11:34:17 09/10/19) JMOR or someone can most definitely correct me if I'm wrong, but I don't believe you have enough resistance in your circuit and its overheating your coil. I think you should be at about 4 amps for your coil. A 12v circuit isn't truly 12v. It's more around 14.5. Using ohms law with the information you've provided 14.5 (volts) 2.1 ( your total resistance) = 6.9 (amps). I think you may need another resistor to bring it down some.
Someone please correct me if I'm wrong. I dont claim to be a professional Shocked
Correct. The reason I had not already chimed in is that while current needs to be reduced, I have a feeling that it will not fix his problem, unless the coil has been permanently damaged, in which case he needs new coil and reduced current.
 
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Kennyp529
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PostPosted: Tue Sep 10, 2019 9:00 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote




I'm going to answer the questions that I know the answers to in bullet format for ease of understanding what I'm trying to say.

1. Coil has 1.4 ohms so I'm assuming that its 6v

2. Old resistor had a ungodly amount of resistance and the tractor wouldn't fire after the rewire so I bypassed it and it fired to life ( so I replaced it.)

3. Wiring is correct. I googled 8n 12v wiring diagram, which brought me to this website and to a comment to us one of JMOR's Pict-o-grams. It was too easy to understand

4. Rewired the tractor because it was a rat's nest of twisted/taped "connections" and someone also used wire nuts instead of butt connectors.

5. Tractor was not running before I started working on it.

6. Before last week, I lived over 1000 miles away from my father. He has 0 mechanic ability so he relied on " the kid down the road" for his tractor "repairs".

I still owe you some answers which I'll post today after I go out to where the tractor is at.

Thanks for the help so far
 
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Kennyp529
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PostPosted: Tue Sep 10, 2019 9:34 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

I forgot to mention that while I was testing the coil resistance yesterday, I noticed a nice big crack down the side of the coil.

Can I replace it with a 12v unit PN : 9N12024-12V.? There is 1 available in town at Rural King.
 
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JMOR
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PostPosted: Tue Sep 10, 2019 10:22 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

Kennyp529 wrote:
(quoted from post at 13:34:43 09/10/19) I forgot to mention that while I was testing the coil resistance yesterday, I noticed a nice big crack down the side of the coil.

Can I replace it with a 12v unit PN : 9N12024-12V.? There is 1 available in town at Rural King.
yes
 
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Kennyp529
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PostPosted: Tue Sep 10, 2019 4:04 pm    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

[quote="JMOR"](reply to post at 11:22:22 09/10/19) [/quote

Installed new 12v coil today and mowed for about 45mins. Shut the tractor off and it starts right up now( repeatedly)

Fixing that problem allowed me to uncover another problem..... IT RUNS LIKE $H!T. When it was idling it sounded like a cammed HONDA (terrible). She also lacked power ( pto enabled and disabled)
I found that if I kept my hand on the choke knob and adjusted it, it would run a little less $H!tty.
 
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JMOR
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PostPosted: Tue Sep 10, 2019 4:09 pm    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

[quote="Kennyp529"](quoted from post at 20:04:35 09/10/19)
JMOR wrote:
(reply to post at 11:22:22 09/10/19) [/quote

Installed new 12v coil today and mowed for about 45mins. Shut the tractor off and it starts right up now( repeatedly)

Fixing that problem allowed me to uncover another problem..... IT RUNS LIKE $H!T. When it was idling it sounded like a cammed HONDA (terrible). She also lacked power ( pto enabled and disabled)
I found that if I kept my hand on the choke knob and adjusted it, it would run a little less $H!tty.
Check/clean all three filter screens in fuel path and if all ok, then disassemble carb for a thorough cleaning of every tiny passage.
 
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Tim PloughNman Daley
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PostPosted: Wed Sep 11, 2019 12:30 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

I gotta ask, how does a coil get big rip/tear in it? Your wiring pictogram would be the best source to use for all electrical wiring on N's. "Ungodly amount of resistance". How much is 'ungodly' and how are you checking it? I don't think I've ever checked resistor values, no need. Don't worry about it -resistors are supposed to get hot, have a lot of resistance. Do the coil test as I said. If wiring is correct, distributor tested OK, and a good coil, all should be right with world. Using a new wiring harness is OK as long as it is wired correctly. Buying a new coil: don't rely on what the box, says check it yourself. Having the kid down the road work on it is fine as long as he knows what he is doing.

TPD
 
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Kennyp529
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PostPosted: Wed Sep 11, 2019 4:18 pm    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

Ok so today i started by draining the fuel from the tank. I disconnected the line at the carb. Inoticed that the fuel flow was poor at times. It would drip, then lightly stream, then flow great, then repeat -- almost in a rhythmic manner. Tank looked great inside ( replaced in the past couple of years. After fuel was drained i washed and blew out the 3 screens. I refilled er and started it up with out any change. A bunch of popping and loping. I was going to try to do a cylinder cut out type test by pulling 1 plug wire at a time but when i reached for the 1st plug boot it shocked the snot out of me. Is this normal.... in not used to working on things with spark plugs.
 
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Kennyp529
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PostPosted: Wed Sep 11, 2019 4:22 pm    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

Also I belive that the quality TIWAN coil cracked from repeated thermal expansion
 
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HFJ
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PostPosted: Wed Sep 11, 2019 5:04 pm    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

Kennyp529 wrote:
(quoted from post at 21:18:52 09/11/19) Ok

when i reached for the 1st plug boot it shocked the snot out of me. Is this normal


yes. that spark consists of a whole lot of voltage.
 
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Tall T
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PostPosted: Sat Sep 14, 2019 9:30 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote

Kennyp529 wrote:
(quoted from post at 17:18:52 09/11/19) Ok so today i started by draining the fuel from the tank. I disconnected the line at the carb. Inoticed that the fuel flow was poor at times. It would drip, then lightly stream, then flow great, then repeat -- almost in a rhythmic manner. Tank looked great inside ( replaced in the past couple of years. .


Sounds like your tank cap isn't breathing.
 
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Kennyp529
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PostPosted: Sat Sep 14, 2019 10:48 am    Post subject: Re: 8n no spark when hot Reply to specific post Reply with quote


Had a similar thought during the draining process. Pulled the gas cap and no change to the flow
 
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