The Stovebolt Site Forums The Parking Lot Big Bolts weak spark

64 327 points type ign. hard starting when engine warm. starts right up cold. I checked the spark when it wouldn't start It looked weak to me.
pushed it off and it started immediately. I just replaced the coil, dwell is set at 28 degrees. Runs great on the road. 5200 miles on it.

is the 'hard starting' in the form of 'reluctant cranking' or turns fine, just won't fire?

next time it's warm and won't start, tweak the timing a wee bit at a time and see if it does start - or try it w/ the dwell at 30-32

Bill

engine turns over fine just won't hit. looks like it would be harder starting cold, but just opposite.
I'm going to try a new set of points and condenser today see if that helps. something is causing that weak spark.

Don,

Don't rule out the carburetor if it isn't a "reluctant cranking" problem. A warm/hot carburetor will sometimes percolate fuel into the engine and give it a flooded-hard start situation. Black smoke would be a clue on start up.

Stuart

Is the spark hotter when the engine is cold?

I ask just because you might ALWAYS have a weak spark, and the non start when warm problem might be due to something else.

If the spark is hot when cold, but gets weak as the engine warms, i'd consider replacing the condenser.

What I need to know now, How many wires go to the + side of the coil. I know 1 yellow one I found that one. (this is a fire truck they had added a wire to the yellow one and ran it to the battry side of the tach on the front) then ran another wire from that terminal back to the + side of the coil.
I was thinking it cranks on 12 volts then switches back to the resistor wire when you let go of the key.

Don,

I think you have a firm grasp on how the coil circuit works...

The key side of the coil (+) needs at least one wire, obviously. It might need two. It would depend on how your truck was wired and if the coil has a internal resistor.

If you have a start/run resistor on the firewall, and it only has one wire going to the coil, then the coil + should have two wires. The other wire will come from the starter solenoid.

If you have no ceramic resistor on the firewall, then the coil will have only one wire. This wire should come from the key switch.

These are FACTORY wires...tachometers and other items might add wires to this post too..I don't know.

Stuart

ive seen coils get weak when hot, and if its cranking fine,,,starter not dragging,,and not too far advanced , kicking..then coil or like the others said....ya dont know how many amps starter is drawing hot vs cold do yah..??? could even be starter,,,or low battery voltage even if it cranks ok......as in starter drawing too many amps dropping voltage to coil...

I got it fixed. they were powering the tach off off the + side of the dist instead of the battery. Anyway, I rewired all that like it is supposed to be.
Now the tach works and it starts after a hot soak.
No external resistor on the firewall. So I am still thinking there should be 2 wires to the + side, cause the yellow wire is 12 volts. Unless that model used an internal resistor coil. Anyway, I have a good blue spark now.
Thanks for the help guys!!!

for reference, you guys ever notice that on some starter solenoids there are 2 wires, one labeled "s" and "i"?

here's the connection. "s" is for starter "I" is for ignition. in the solenoid is the ballest resistor for the points. that's why you very rarely see an external resistor on g.m. vehicles. it has one already. the vehicle starts on 12v, and after you let off the key from the start position it goes back to 9.6.

Hy guys, I've never seen a ballast resistor in a solenoid. I've seen ceramic ballast resistors on firewalls, and I've seen resistant wires in the vehicle harness

koolkar,

It's time again for atomarc to go way out on a limb...I'm going to run down and look at my Motors Manual because I haven't ever heard your theory about the/a resistor in the solenoid.

The typical place for a resistor was smack dab on the firewall of a GM rig. I always remembered that Fords used a resistance primary lead wire.

I think the "I" terminal on the solenoid is a normally open contact to battery voltage. The big old copper disc slams back when the solenoid is energized and "makes" this post hot. The same big old copper disc energizes the starter.

Boy, I hope I don't have my head up my @#$*&! on this theory.

Stuart.

no Stuart, yer about right - the 'I' terminal puts full batt voltage to the coil while the starter is engaged, foot stomp or key

the reason[s] you seldom see the firewall mounted ign resistor KK, is that they didn't have'em in the 6 volt years, and after the 60's they had internally resisted coils so could put full 12V to the coil alla time - they were only used about 6-8 years

Bill

I just chugged back up from the shop where I looked in the Chiltons and Motors Manuals and they show the the solenoid supplying battery voltage to that terminal in the "resistor bypass mode"...when the solenoid is drawn in (energized).

I'm not trying to one-up anyone, or be a smart arse, but I need to know if I was out to lunch when "starters 101" was in session. :o

Stuart

I'm still not going to be 100% happy until someone with a 64 looks at the coil and tells me how many wires go to the + side of the coil.
I say that because I had the NAPA store pull a new coil for my 64 and it said "use with external resistor" But, the original coil only says 12 Volt Delco.
I know what happens if you put 12 volts to a coil not designed to have 12 volts....it will explode and make a terrible mess. I sure don't want that.

Don,

Nothing is going to explode. You had this all figured out in an earlier post...did the NAPA guy rattle your cage. There are two common ways to reduce the voltage so the points will last longer, they are both exactly the same, but one is hidden where you can't see it.

If you see the ceramic ballast resistor on the firewall (or somewhere) you use the standard coil. If you don't see the resistor on the firewall (or somewhere), use the coil with the secret resistor hidden inside.

The points will see the same voltage either way! With BOTH these systems, the ignition system WANTS the full whammy when it starts..12 volts. It is just for a few seconds and it allows the vehicle to start easier because you are using a bunch of juice to actually spin the starter.

My friend has a '64 and he has one wire on the coil...do you believe me? Find a factory wiring diagram for your truck. It will show you precisely how many factory wires it should have.

The only thing that would affect your truck is if you had no wires on the key side of the coil.

So the answer is..with a external resistor you could have one or two wires, depending on how it was wired...with an internal resistor coil, you would only have one wire.

My question to you is...how do the points get full battery voltage when you use a internal resistor coil. I haven't figured this one out!

Stuart

hey! what's w/ a 327 in a 64 anyway? everything I've seen sez it wasn't available in trucks till 66 [one book sez 65] - is the 327 supposed to be original? is the wiring all original? no cut or added wires? maybe that tach wire was the one that should go to the starter from the coil?

as Stu sez, the coil will not explode, it will merely fail prematurely because it'll be running too hot w/o the ign resistor - all you gotta do is ask the parts guy for an internal resistance 12V coil - they're alla same

if the truck originally had an external resistor and has the original wiring, it will have 2 wires on the coil - one goes to the small terminal on the side of the starter solenoid and is hot only when cranking, one goes to the external resistor, which gets juice from the ign sw - w/ internal resistance it will have one wire, to the ign sw, hot only when the key is on

not atomic physics - just get the coil that fits the setup!

oh yeah, Stu - the points get full COIL output voltage [10,000V?], it's the coil input that gets the 12V

Bill

That's not correct, the points ground out the 12 volt Primary Winging of the coil, which is more like 9 volts when it's running through the ballast resistor. The HIGH voltage Secondary Winding is grounded at the sparkplug when it jumps the gap. The High Voltage spark happens every time the points OPEN. This is due to the collaps of the magnetic field inside the coil, which in turn makes a low amp-hi voltage spike that is allowed to jump the gap at the spark plug at just the right time.

If you install an Internal Resistor type coil you will not get the full 12 volts when you try to start the truck. There is no way to by-pass this resistor. I believe most of the Internal Resistor type coils were used on small engines (farm and gargen tractors etc.).

Your Tach should be connected to the distributor side of the coil, not the battery side.

Hope this helps...

Happy Holidays!

Mike B

yer right Mike, I was just thinking on the fact that the problem w/ full 12v to the coil is hot coil not burned points - the unresisted coils are designed to have that external resistance, the internal resisted ones work fine as I've had them on a number of 283's

internal resisted ones were/are used on these trucks when no external resistor is used - maybe the first 12v coils were actually 6v ones w/ the resistor added? the problem w/ too much voltage/heat on the coil is it damages the varnish on the winding wire over time

Bill

Red58 I just checked . The 64 C-60 did come with a 327. It is right in my owners manual.
This truck only has 5,162 miles on it and has been garage kept since day 1.

aah a big truck - ok the bigger engines always were available as options in big trucks a year or 2 before the light trucks - shoulda payed attention to the forum I was in!

Bill

The ballast resistor for the 60-66 trucks was in the wire between the coil and the starter. No ballast resistor in the solenoid or mounted on the firewall.

Vaughn,

Very interesting. I did not know GM used resistance WIRES!! but you are correct. I enclosed a link that talks more about that system on a '66 truck.


http://www.yesterdaystruck.com/trforum/messages/13068.html


Stuart

And after measuring battery voltage at the coil + I found that the yellow wire supplies bat voltage when the key is turned to start and drops back to 9.2 volts when running (really cheap volt meter)
Great posts Guys I think we all got a good refresher.
And the best part is my truck is fixed!!!!
THANKS

Don,

You found your answer...it is ONE YELLOW wire!

Stuart

Just for fun...no one get upset, PLEASE

How many forum posters does it take to change a light bulb?

1 to change the light bulb and to post that the light bulb has been changed

14 to share similar experiences of changing light bulbs and how the light bulb could have been changed differently

7 to caution about the dangers of changing light bulbs

1 to move it to the Lighting section

2 to argue then move it to the Technical section

7 to point out spelling/grammar errors in posts about changing light bulbs

5 to flame the spell checkers

3 to correct spelling/grammar flames

6 to argue over whether it's "lightbulb" or "light bulb" ... another 6 to condemn those 6 as stupid

2 industry professionals to inform the group that the proper term is "lamp"

15 know-it-alls who claim they were in the industry, and that "light bulb" is perfectly correct

19 to post that this forum is not about light bulbs and to please take this discussion to a lightbulb forum

11 to defend the posting to this forum saying that we all use light bulbs and therefore the posts are relevant to this forum

36 to debate which method of changing light bulbs is superior, where to buy the best light bulbs, what brand of light bulbs work best for this technique and what brands are faulty

7 to post URL's where one can see examples of different light bulbs

4 to post that the URL's were posted incorrectly and then post the corrected URL's

3 to post about links they found from the URL's that are relevant to this group which makes light bulbs relevant to this group

13 to link all posts to date, quote them in their entirety including all headers and signatures, and add "Me too"

5 to post to the group that they will no longer post because they cannot handle the light bulb controversy

4 to say "didn't we go through this already a short time ago?"

13 to say "do a Google search on light bulbs before posting questions about light bulbs"

1 forum lurker to respond to the original post 6 months from now and start it all over again.

hi don. boy you sure like to type! i gues i have to stand corrected for being olny partially right. the info i gave was given to me many years ago, and i have always thought it rightsince the voltage at the coil was------9.2. to 9.6. that seemed to confirm what i was taught.

so, tonight i learned something.

uhhhhh, don, maybe THAT'S more what it's all about. learning.

Don,

Pretty darn accurate..and funny too. It gives me the creeps though, I think I fit about half of those profiles. Maybe I'll slink to the background and watch the circus for awhile.

P.S. Maybe this is what happens when you have 9000 registered light-bulb checkers in the same room.

Stuart