Voltage at (-) side of coil?

[SSTKO81]

Ok so after a rough run of luck with my ignition I've got good spark again but she just won't quite start. I ran a few tests at coil and found that w/ the ig on but not running I've got 12v, when I crank I've got 12v, and I have 12v on the (-) side ofthe coil too. Normal? Cause???

 

[bruceb58]

Re: Voltage at (-) side of coil?

Normal to have 12V on the negative side of the coil when the points are open.

 

[SSTKO81]

Re: Voltage at (-) side of coil?

Well that's a a relief.-kinda. Still runnin too much juice to the coil in run. Should be down around 7-10 from what I understand. But even still that wouldn't keep the motor from starting.

 

[TiredoleBoy]

Re: Voltage at (-) side of coil?

fuel?

 

[HT32BSX115]

Re: Voltage at (-) side of coil?

Well that's a a relief.-kinda. Still runnin too much juice to the coil in run. Should be down around 7-10 from what I understand. But even still that wouldn't keep the motor from starting.

Um, if the points are open, you'll STILL get "too much juice" in run.

The dropping (ballast) resistor will only drop the voltage if there's current FLOWING though it (points-closed).

There'll be NO current flowing when the points are open. (open circuit= Zero current)


Cheers,


Rick

 

[Bt Doctur]

Re: Voltage at (-) side of coil?

considering we dint know what ype if ign. you have were guessing.For electronic. types +12v because the resistor is in the coil.For points 7-9 because you have a ballast resistor and the coil says"Use with external resistor". Also there is a difference in the "ohm`s value"
between electronic and points coils

 

[SSTKO81]

Re: Voltage at (-) side of coil?

Now my battery is too week to keep cranking. It's still not starting. But it's so so Close! I'll let it charge for a while and see what happens. I've got spark, fuel, and air. The only thing left is timing. Anyone ever seen #1 almost at the top of the dist when looking from the side? Oh and as an after thought I've got points with the resistor wire, and the coil says on the side "use with resistance wire or external resistor"

 

[Bt Doctur]

Re: Voltage at (-) side of coil?

"I've got points with the resistor wire, and the coil says on the side "use with resistance wire or external resistor"

The resistor wire/ ballast resistor goes on the + side of the coil.
The rotor can point anywhere depending on how the dist was installed.You should bring #1 to TDC compression stroke. see where the rotor is and call that number1, install the wires in a clockwise pattern.

 

[JustJason]

Re: Voltage at (-) side of coil?

When was the last time you changed the points and condesor, set the dwell, and set the timing?

 

[SSTKO81]

Re: Voltage at (-) side of coil?

Ok double checked and dist and wires are all right. The points, condenser, cap, and rotor are all new. I'm not sure how to set dwell, so that could be worth a look... I did actually get it to start for a second, but as soon as I throttled down It died. Kinda wondering if it's fuel related rather than electrical. My luck it's both.

 

[JustJason]

Re: Voltage at (-) side of coil?

If you didn't set the dwell and base timing it's not going to idle right.

 

[HT32BSX115]

Re: Voltage at (-) side of coil?

For electronic. types +12v because the resistor is in the coil

A Moot point (or MUTE point for those of you in Rio Linda)...........But, coils are not made with a "built in resistor"....... They're just a coil wound with the correct resistance primary winding to operate at 12v.....


You don't have to worry about dwell if you set the points gap correctly. GAP= DWELL, DWELL=GAP ........ both roads lead to the same place.....


It sounds like your problem is fuel, not ignition......

 

[TiredoleBoy]

Re: Voltage at (-) side of coil?

fuel?

I will repeat.

 

[bruceb58]

Re: Voltage at (-) side of coil?

You need to set the dwell with a dwell meter. Gapping is not good enough. Once you set the dwell, then you set the timing. Until you verify both of these, you are just chasing your tail.

It does sound like fuel but you need to get the ignition set correctly first which it doesn't sound like you have.

 

[JustJason]

Re: Voltage at (-) side of coil?

I'm gonna disagree with you Rick. Gap get's it close enough to run. Dwell dials it in. Biggest problem is no two people (unless they are both mechanics or machinists) will can set a gap to .020 and be on the money. But almost everybody should be able to make a needle hit a number on a dwell meter.
And since dwell and timing go hand and hand, you need to get the dwell set before you can set the timing.

 

[amdburner]

Re: Voltage at (-) side of coil?

It sounds like the dwell is off to me as well. I just went through this 2 days ago with my "new" 1985 Century Mustang 3.0L. I set the initial gap setting according to specs found in manual #13 for a newer 3.0L (.016) and then adjusted the dwell according to the same specs (39 to 45 degrees). Needless to say the engine would not start. It would fart once in a while but nothing more. I should have known better as having dug around in these forums put other numbers in my head than what was in the manual. So, I reset the gap to 0.021 and the dwell fell to around 34 degrees. Gee, the engine started without hesitation that time...... I fine tuned it to around 30 degrees and then set the initial advance to 6 degrees BTDC and called it good until I can get on the water to test it under load. So, get the correct specs for your engine and set the points correctly and all should be much better for you.

 

[SSTKO81]

Re: Voltage at (-) side of coil?

The more I read up on this (thank you AMD, Jason, and Bruce). The more it really does sound like dwell/gap. My engines doing exactly as described. -practically running while the starters going, "farting", and then a sputtery death.... I've got a good set of feeler guages handy so I'll crawl in there and check out the gap (fraid I don't have a dwell meter) and if I can get it running I'll be able to time it up correctly I hope.
As far as the fuel situation, think i was a little lean. I'll juice the carb up and see how she goes.

 

[bruceb58]

Re: Voltage at (-) side of coil?

So how have you set the dwell and timing up to this point?

 

[JustJason]

Re: Voltage at (-) side of coil?

You can get a combo dwell meter/shop tach at sears for 30 bucks. You need to set the dwell before you set the timing, in that order. Throw out your feeler gauges and just eyeball the gap, because it's the dwell number that your really after.

 

[6meter]

Re: Voltage at (-) side of coil?

Do a quick squirt of starter fluid or carb claener in the carb. If it starts for a second or two,you have a fuel problem. If it doesn't, ignition. Sounds to me that your timing is not advanced enough.