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Discussion Starter · #1 ·
Hello everyone. First post here. I'm 19 and recently bought a 1970 malibu. It has a 350 crate motor in it with much of the stock extras removed (no AC components, heater gone ext).

Anyway i towed it home and did a minor teardown (intake+exaust manifold, valve covers) to see what kind of shape things appeared to be in. Supposadly it only has about 20k on the motor and there wasn't a spec of sludge in it to back that up.

Put it back together and tried to start it and no spark. Took the ignition coil off and grounded it. (hold the wire near body, would arc if it was getting power) Got nothing. Also used one of those lights that plug in between the plug and wire and confirmed no spark. Dad (used to have a charger but has a horrible memory) plus another guy suggested it's probly a coil. So got a new one and same story.

Here's what i've found out. The posative post on the coil has power on run and on crank. While cranking using a test light on possative and on the neg terminal of the coil it flickerd (from what i can see this means the points are working). However the starter DOES crank slowly. Has a bad battery but i used my truck to jump it. I do not have a wiring manual so i'm gessing how it works partly from looking at it. I am in school for automotive tech but we're only learning the new stuff so i don't know much about points and how this system actually works.

I have to have this thing running because where its parked is we get any snow during the winter i'll have to move it for the plows. Not working do to school and the bills don't stop for that unfortunatly so i can't afford to take another guess. I was thinking based on the fact the + side of coil has power and the neg side is grounded and unground (through the points i'm guessing) that the NEW coil could be bad.

What do you guys think and recomend. Tnx for the help
 

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Steve,

Here's a basic rundown on how the coil works, without going into too much detail. You have ~12 VDC on the (+) side of the coil. The other side of the coil is attached to the points, which are attached to the ground (Neg terminal of the battery). When the points close, you place 12 VDC across the outer coil (of your coil). This generates a quickly expanding electric field. The points open, the electric field collapses, and induces into the inner coil, thus generating the voltage to fire the spark plugs. Same basic idea of the electronic type you are learning now.
So if you have the 12 VDC and the points are working (and have a good connection to the chassis), the coil should fire off. I would suggest that you first check to see if the coil itself is firing. Then move on to see if it's getting through the distrubitor. I'm sure other's will have a better or more detailed suggestions.

SS4speed.
 

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Discussion Starter · #3 ·
Tnx for the reply. Thats exactly how i was guessing it worked
I have power on the + side when key is on and cranking and the negative terminal cyles between ground and open. Because the negative it cycling the points are working corectly i'm guessing. When the neg post is grounded from the points curent can go through the primary coil. When the points open the curent is cut and that fires the secondary coil which sends the high voltage that is generated to the distributer. I do not have spark from the ignition wire from the coil. Tried a spare wire i had lying around too so i know its not the ignition coil wire. Have B+ going in and the cycling negative and no charge out the top so i'm thinking the new coil is bad too right?

The starter does crank slowly and after a few cranks last night my friend said he saw some smoke from it. Might have a bad conection and some arching or a bad batery cable down there but I'm guessing that because i'm getting + to the coil from the selenoid that the starter and selenoid have nothing to do with no spark regaurdless of what they are doing. All this make sense?
 

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Steve,
Take the distributor cap off and the rotor then inspect the points. Have someone crank the engine a bit and see what's happening with the points in there when the engine cranks over.

There is a resistor in the circuit when in the run mode, but not in the crank mode. This reduces current through the points to keep from burning them up. If this resistor (usually long rectangular white device with wires on each end) opens up or losses a connection you have troubles.

If the points contacts aren't very flat, and don't open and close properly, your coil won't get what it needs to fire off. You can file these flat again ....to a point, in an emergency.

Also check the condition of your wires, distributor cap and rotor.

Another thing that frequently went bad and should be checked or changed is the "condensor", which is really a large capacitor, but call it a condensor when asking for it at the parts counter. Not that anyone under 35 behind a parts counter would know what they are in the first place.

Usually you asked for "points and condensor". If the condensor is bad you will have major troubles as well.

If all of that is good, you still need to have the points adjusted right to get a decent amount of juice to the coil. It's doubtful you will have a "feeler guage" that measures the gap, but the old rule was use a match book cover when the distributor cam lobe was at a high point on the points rubbing block ...which opens the points up. Loosen the end screws, and use a flat bladed screw driver in the slots in between the points and distributor base...if I remember right.

Then lose the points for Electronic Ignition...preferably HEI when you can afford to do so.

Ole fart Steve
 

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Steve,

If my memory is functional at all, everything you stated is correct. Point one, I would be hard pressed to think that the new coil is bad, unless it was somehow damged (which is not too likely).
Therefore, I wonder if the coil is really working, but it just has a very very weak spark.
I don't have any real suggestions, but maybe this will help point you in the some direction.
One items you stated,

"and the negative terminal cyles between ground and open."

The negative terminal (if I remember correctly) should cycle between ground and 12 VDC when measured with a voltmeter. I would think that if you lifted a wire in a circuit, the potential would be at that wire (in reference to your batt neg terminal). So when the contacts are closed, you should see 0 volts and when the contacts are open you should see 12 VDC (on the negative coil terminal).
On your statement at the end:
"The starter does crank slowly and after a few cranks last night my friend said he saw some smoke from it. Might have a bad conection and some arching or a bad batery cable down there but I'm guessing that because i'm getting + to the coil from the selenoid that the starter and selenoid have nothing to do with no spark regaurdless of what they are doing. All this make sense?"

Yes, this makes sense, and may also be generating a weak spark also. The coil does not need a lot of current, but if the current was limited by a partially broken wire, then it's possible that you could be getting a very weak spark. If I remember anything from an Electronic course I took (in college many many years ago), the voltage is only potential, and is present even with very little current flow. So the voltage at the end of a wire will be 12 VDC, if you have one stran or twenty strans (ignoring solid core wire). Maybe the bad connection to the starter, a bad starter, or the wire to the coil, could be the problem, (wild guess on my part). Don't just replace the (+) coil wire going to the starter, I believe it's a resistor wire. I know my 1969 Chevelle has one. It drops the voltage below 12 VDC. One more misc item, I have never seen a bad coil that can be measured (with a ohm meter) between the plus and minus coil terminals. (I may have a bunch of people beat me up on that statement.) It will be a very low reading, I think around 5 - 6 ohms or so.

SS4speed
 

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Discussion Starter · #6 ·
Tnx for the info Steve. I looked at the points earlier when i was messing with it and they apear to be brand new. The distributer cap, points, rotor, and condensor all look new. Car sat for 1 and a half years however. Supposadly it ran when it was parked though.

I have a few feeler gauges. I tried looking up the gap earlier (i don't have a book for it) and came up with .019" gap. That sound about right? I'll set the gap to that and see what happens later when my buddy comes over. Don't remember a resistor off the top of my head but I didn't look for one when i was out their earlier. I'ld imagine its new as well though.

One thing i did notice is the wire that runs from the bottom of the distributor to the coil is old and not looking to good. Because the ground was closing and openin at the coil post (the neg post, put a test light from there to positive batery terminal and it flickered as i expected) i just assumed that it was working. Lets say i set the gap on the points and i have the same issue. How would i check the condensor and resistor or continue from there?


Tnx agian SS4speed. Hi resistance in a wire (bad conection which the batery cables at the battery look very bad) would reduce amps. That could be accounting for the slow crank and the smoke. i'll check the conections at the starter later as well. As stated to steve the wire to the neg coil post looks pretty beaten so i'll replace that one to be sure (no resistor or anything in it). Any idea how many amps i should be getting to the coil? If i could check that it would confirm wether or not i was the result of high resistance in a wire or conector. Off the top of my head 5 or 6 amps i believe is whats used in ignition coils but i could be wrong. I'll check that too and see what i get.
 

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One thing i did notice is the wire that runs from the bottom of the distributor to the coil is old and not looking to good.
I can't tell you how many times I found a faulty primary wire to be the culprit when working on point ignitions. If the insulation breaks down and shorts to the distributor body you will not get it to fire. Should be the ultimate cheap fix too.
 

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According to one manual I have, it states that a coil should measure around 1 ohm if it has a resistor wire, and 4 ohms if it does not have a resistor wire. Based on that, your coil should be around 1 to 2 ohms. If that's correct, I would expect you to see somewhere around 5 to 10 amps or so. 10 amps seems high to me, but maybe it's not when you think about some of the HO coils. That's all ballpark values, but it should be somewhat close. As misc note, make sure that your Neg cable is solid also, as it can cause some of the same type of problems. Just curious, does the Neg battery terminal go to the Engine block? If not, make sure to check you grounding cables also (just a thought).

SS4speed.
 

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Discussion Starter · #9 ·
Update

Got it running yesterday. Ended up replacing a primary coil wire, cleaning and gapping the points, and replacing the battery cables. The B+ cable was actually burned through to the wire near the starter and had electrical tape covering it. Probly was giving me a partual short.

Tnx for all the help guys
 

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Glad you got it going
 
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