starts when let up

[rnorum]

My '49 8N, 12V Conversion, 6 V coil with extra resister, I am never sure how to use the tester on the coil.front mount will now start only when releasing the starter button. I burned up one starter and now I have a
ford tractor specialist rebuilt starter that spins over good but seems like the sparkies don't have enough spark under compression, (do plugs fire different under compression?) but I cant see that. I have a 3/16" blue spark out side on the manifold ground. Should I take of the dist again (13th time) and could the timing be too late? causing hard start? Would appreciate any advice.
Thank you, DN

 

[Bruce (VA)]

" (do plugs fire different under compression?)"

Yes.

" and could the timing be too late? causing hard start?"

Probably not.....but why didn't you set the timing on one of those 13 times?

" 6 V coil with extra resister, "

Did you measure the current or resistance in the circuit before you installed that "extra" resistor? Because if you didn't, that's the likely cause of your weak spark.....too much resistance in the circuit.
50 Tips

 

[Dean]

It's not ignition timing.

Engine starting upon stater switch release is a classic symptom of poor spark, often (not always) caused by low primary voltage.

Measure the primary voltage at the coil with an ANALOG meter with the points closed and during cranking.

If you do not have a decent analog meter, simply verify that all primary wireing (including battery cables) is adequately sized, all connections are good and the battery is fully charged. Verify also that the ignition resistor is of the proper resistance value and wattage rating.

Yes, compression and fuel mixture do affect break over voltage of spark plugs.

If the plugs have been badly flooded, sandblast or replace them.

Dean

 

[rnorum]

Thank you for answering. 13 times is a long story. breifly, bought a new dist and the center shaft with the bumps on it was off aprox 20 degrees, coud'nt time, sent it to where I bought and it come back with timing screw and plate way off to one side and would just barely run. then the post that hold the points had a loose rivet, so I tightened that and then I keep second guessed my self many more times. Just now, I cant start or fire even when I let up button. So I am back to zero. Rebuilt engine w/125 lbs comp, GB Carb, copper wires, 6 V coil with resistor from NAPA, new points Blue streak with vent hole @ 15. I even took off the manifold, replaced gaskets yesterday and saw no leaking,on previously surfaced manifold and reset tappets Out of desperation I ordered a 12V coil and resister (he recommended) from dennis C and his parts man said I have to have a resister beside the original one to operate, It don't sound right but I really don't know.

Thanks again, DN

 

[rnorum]

That makes sense. What am I looking for amps or volts? What procedure should I do?
Hook my meter to top of coil and ground, turn on key and see what? Then turn engine over a little to see differences in reading when points open and close? What should the readings be?

Thanks for the help, DN

 

[ZANE]

Lots of engines made after about 1955 use a starter solenoid that has four posts on them. The two big ones are to engage the starter. One of the two small posts is to energize the solenoid and turn the starter. The other one is what you need on your tractor. It bypasses the resistor/s in the ignition circuit and allows full battery voltage to go to the ignition coil during the starting only and when the engine starts the resistor igniition is once again the only current to the coil.

Get yourself a starter solenoid that was made to fit something like a 1960 Ford car. The small posts will be marked "I" for the one to the coil @ignition, the other will be marked "S" for the starter switch to go to.

Zane

 

[rnorum]

That sound good. I am going to find one today.
What should the voltage be to the coil, before cranking and after cranking?

Thanks for help, DN

 

[R Geiger]

(quoted from post at 23:31:03 12/22/11) Lots of engines made after about 1955 use a starter solenoid that has four posts on them. The two big ones are to engage the starter. One of the two small posts is to energize the solenoid and turn the starter. The other one is what you need on your tractor. It bypasses the resistor/s in the ignition circuit and allows full battery voltage to go to the ignition coil during the starting only and when the engine starts the resistor igniition is once again the only current to the coil.

Get yourself a starter solenoid that was made to fit something like a 1960 Ford car. The small posts will be marked "I" for the one to the coil @ignition, the other will be marked "S" for the starter switch to go to.

Zane

I sure would hate to get this tractor down the road. It will be a total mess. I agree that it would probably work but why not fix the real problem instead of this. Just saying!

 

[Bruce (VA)]

I just told you that you probably have a ignition resistance problem because of too much resistance in the circuit....and you reply that the Dennis Carpenter folks tell you to use a resistor w/ their 12v coil. Well, either they are telling you to use the OEM ballast resistor (which is correct) OR they are not selling you a 12v coil.

You have a low voltage problem.

Yes, you can get another solenoid.....and further complicate the problem. Or, you can find the reason for the low voltage & fix it.

" sent it to where I bought and it come back with timing screw and plate way off to one side"

That doesn't answer the question. Have you timed it or not? If not, just say so & you can get some help doing it. But that's not the cause of the low voltage problem.
50 Tips

 

[Dean]

No.

No resistor with 12V coil, unless you retrofit your system with a cranking bypass circuit, which is needless complexity for your N.

You've found your problem.

Dean

 

[ZANE]

If it has the original 6 volt coil the voltage to the coil with the points closed should be about 3 volts.

When using the solenoid to bypass the resistor/s it will have battery voltage till it starts.

If it doesn't start with in a few seconds stop cranking or it will damage the coil or points.

Zane

 

[JMOR]

(quoted from post at 14:31:47 12/22/11) If it has the original 6 volt coil the voltage to the coil with the points closed should be about 3 volts.

When using the solenoid to bypass the resistor/s it will have battery voltage till it starts.

If it doesn't start with in a few seconds stop cranking or it will damage the coil or points.

Zane

ey, norum.......when all else fails, put your old distributor/parts back....sounds like some bad 'new' Chi-Com stuff to me.

 

[BillM (OH)]

I would replace the 6V square can coil with a 12V square can coil and use only the ballast resistor in the ignition line. Sounds like you have too much resistance in the ignition wiring to the coil. Others have eliminated the square can coil and installed a round can 12V coil needing no resistance, but that requires some extensive modification which you may not want to tackle.

 

[36 Coupe]

Use a hydrometer to check the battery.Just replaced the battery on my grand daughters car.It was cranking slow on cold mornings.Battery showed a 1/4 charge after a 30 trip.Charge voltage was at 14 volts.New battery fixed the problem.A hydometer can show uneven charge rates in each cell,That predicts failure, usually a frozen cell.

 

[Hobo,NC]

(quoted from post at 17:21:39 12/22/11) My '49 8N, 12V Conversion, 6 V coil with extra resister, I am never sure how to use the tester on the coil.front mount will now start only when releasing the starter button. I burned up one starter and now I have a
ford tractor specialist rebuilt starter that spins over good but seems like the sparkies don't have enough spark under compression, (do plugs fire different under compression?) but I cant see that. I have a 3/16" blue spark out side on the manifold ground. Should I take of the dist again (13th time) and could the timing be too late? causing hard start? Would appreciate any advice.
Thank you, DN

I suspect you have a falling coil,,, Bruce can fill you in on using a spark tester I prefer the adjustable type set to 20K (1/4"),,, 3/16 will not get'er done....
A nice up-grade is to convert to a round can IC14SB coil....

 

[rnorum]

Jmor,
Thanks for answering.
I am going to learn even it it kills me about volts ohms etc.
I just rewired to match your scematic for 12V conversion (I had it all wrong) and I have a new coil 12V,coil ohms is 1.5. This morning I wiggled my ballast resistor (the one with all the wires hooked to) and it sparked with bottom post hitting the body and was burnt on the back side where the lock screw was loose screw was touching I had a new one and just put it on. Checked ohms and it is .4 I have not figured out what to use for a extra resister? I have one that reads 2.2 ohms, I need more advice. DN

 

[Bruce (VA)]

" I need more advice"

My first bit of advice is to read what you are getting for responses to your questions.

You say " I have a new coil 12V,coil ohms is 1.5." and "I have not figured out what to use for a extra resister? "

As I have repeatedly told you, you DO NOT need another resistor w/ a 12v coil. You do NOT have a 12v coil if it measures 1.5 ohms.

" I am going to learn even it it kills me"

Fine. I will explain it.

Technology & materials being what they were in the 30's, that square coil would melt if it ran on much more than 4 amps for any length of time. (see tip # 38 for an example). In order to get a hot spark at the same time the starter was drawing max current from the battery, a ballast resistor was added in the ignition circuit. What that did was add about .3 ohms of resistance in the circuit, added to the 1.5 ohms of the coil. That got you 3.5 amps or so at start up. As the voltage increased when the engine was running to about 7.5 volts, the resistor heated up, adding more resistance in the circuit. 1.0 ohms hot, plus 1.5 ohms of the coil got you down to 3 amps or so to keep from melting the coil. The same rule (actually, Ohm's Law) applies to a 12v circuit. I= E/R. Current equals voltage divided by resistance.

It used to be before the "Land of Almost Right" started making coils that you could count on a 12v frontmount coil as having 3 ohms of internal resistance & the 6v coils as having 1.5 ohms or less. Thus, thanks to Ohm's Law, you could calculate what additional resistance you needed in the circuit to limit coil current to 3.5 amps. Your new "12 v" coil reads 1.5 ohms. Your OEM ballast resistor (which you must use) is about 1 ohm hot. A coil a 1.5 ohms, plus the ballast resistor at 1 ohm (hot) gives you 2.5 ohms resistance in the circuit. Your 12 volt alternator puts out 14.5 volts. You need to determine current (amps). 14.5 v divided by 2.5 ohms gets you 5.8 amps. Not good!

Lets do the math w/ your 2.2 ohm resistor. 2.2 + 1 = 3.2 ohms. 14.5v divided by 3.2 ohms gets 4.5 amps.

Still to much current!

Now, lets do the math w/ a 2.5 ohm 12v coil.

2.5 + 1 = 3.5 ohms. 14.5 v divided by 3.5 ohms is 4.1 ohms.

Close enough to 4 amps.
50 Tips

 

[rnorum]

Bruce,
Thanks for trying to explain.

If I use the new 12V coil that has 1.5 ohms and add a resister that reads 1.6 ohms, that will be 3.1 ohms. Will that work?
I called Dennis Carpenters tech man twice to ask if this is a 12V coil or not and he says it is and you have to use this resister1.6
And what am I checking at the coil when turn key on and turning over, amps or volts??? and where is amps on my tester? (its a digital with pictures)?

Thanks again,

DN

 

[R Geiger]

(quoted from post at 01:29:54 12/24/11) Bruce,
Thanks for trying to explain.

If I use the new 12V coil that has 1.5 ohms and add a resister that reads 1.6 ohms, that will be 3.1 ohms. Will that work?
I called Dennis Carpenters tech man twice to ask if this is a 12V coil or not and he says it is and you have to use this resister1.6
And what am I checking at the coil when turn key on and turning over, amps or volts??? and where is amps on my tester? (its a digital with pictures)?

Thanks again,

DN

Stiell too much current flow. Do the math

 

[JMOR]

(quoted from post at 12:29:54 12/23/11) Bruce,
Thanks for trying to explain.

If I use the new 12V coil that has 1.5 ohms and add a resister that reads 1.6 ohms, that will be 3.1 ohms. Will that work?
I called Dennis Carpenters tech man twice to ask if this is a 12V coil or not and he says it is and you have to use this resister1.6
And what am I checking at the coil when turn key on and turning over, amps or volts??? and where is amps on my tester? (its a digital with pictures)?

Thanks again,

DN

lose enough....just don't leave key on with engine stalled.....
Get it running & then worry the fine details.

Personally I am suspect of the 1.5 ohm coil....odd number & difficult to obtain accurate Ohm measurements of low ohm values down around 1 ohm. So don't worry about it.
If stalled current is 4 or even 5 amps, the run current will only be about 33% of that or about 1.3amps or 1.7amps.