no spark from plugs, but coil gets spark.

[fierochris]

I now have my carb issue figured out and was attempting to start the car today. but its not getting spark though the plugs, it does however make it to the coil. the cap and rotor seem to be in good shape. any wiring that would cause this?

[Zeke]

Not that I can think of. First, use an Ohm meter on your rotor.

[Lukesportsman]

Have you pulled the plug out, ground it and see if it fires outside the combustion chamber? SAFETY percautions !!

Are the plugs dry? When playing with carbs and there's no spark, check for fouled or wet plugs.

[fierochris]

Originally posted by Lukesportsman
Have you pulled the plug out, ground it and see if it fires outside the combustion chamber? SAFETY percautions !!

Are the plugs dry? When playing with carbs and there's no spark, check for fouled or wet plugs.

yes i grounded the plug. i used a new plug to test it

[TerryH]

I'm guessing the points aren't opening or are burnt. I'm also guessing you have points. Not sure what year we're working on.

[fierochris]

Originally posted by TerryH
I'm guessing the points aren't opening or are burnt. I'm also guessing you have points. Not sure what year we're working on.

its a 71 T 2.2

[TerryH]

Originally posted by fierochris
its a 71 T 2.2

sooooooo........ are the points arcing? I bet not.

[Zeke]

Maybe I didn't understand his post, but if the coil is shooting, then the points are working, no? But, somehow, that spark is not getting to the plugs. Not to be smug, but where would you look?

I could be wrong, and I'm guilty of leaving the rotor on the bench, too, and then wondering why no spark. Doh.

[fierochris]

Originally posted by TerryH
sooooooo........ are the points arcing? I bet not.

not enough, or not any spark to make it arch. the only spark is coming from the coil

[fierochris]

BTW the coil is making spark as soon as you turn the key into the on position. not when you turn it over

[TerryH]

Originally posted by milt
Maybe I didn't understand his post, but if the coil is shooting, then the points are working, no? But, somehow, that spark is not getting to the plugs. Not to be smug, but where would you look?

I could be wrong, and I'm guilty of leaving the rotor on the bench, too, and then wondering why no spark. Doh.

No, you're right, Milt. But you know how points are.... if there's a weak spark in those old ignitions, it's probably the culprit.

Back in the olden days, I used buy points by the 12 pack and I think they came with condensors.

[Alan L]

Assuming the spark is getting to the cap, if the condensor is dead, you will get no useful spark at the plug either.
There is a way to check the condensor, but I can't remember it. But there are not too many options from the cap to the plug, and replacing the condensor is not expensive. With the ignition on and the points on closed, you should get a spark by opening them with an insulated screwdriver, - each and every time. If only once or twice, then condensor not charging up enough.
Make sure the pin in the top of the cap is not jammed up, short of contacting the rotor - assuming the rotor is in.
If the cap has a crack in it, it will earth out rather than fire down the high resistance leads. It needs to be well insulated, not earthed.
Alan

[Zeke]

New ball game. How he tells us the spark for the coil is only a one time spark when he puts power to it, but not when cranking. I'm out.

[fierochris]

Originally posted by milt
New ball game. How he tells us the spark for the coil is only a one time spark when he puts power to it, but not when cranking. I'm out.

we tested it again, thats exactly whats happening. i remember this issue on one of my old V8 American cars. it came down to a ballast resistor.

such an issue with a 911?

[Alan L]

When the condensor is shot, it will not repeatedly recharge quick enough to keep up with the points. They are bouncing around at 000's of rpm (or at least 00's on start up), and the condensor needs to charge at the same rate for a spark. As the condensor ages, it leaks charge across the barrier that is supposed to allow it to build up the potential difference in voltage. So it simply can't build up and hold enough voltage quick enough to deliver a spark. But in a static test may be able to do so once or twice, or at very slow openings. I would definitely throw the old one out and see if it makes a difference.
Another option is the battery using all the power to crank the motor? If the battery is in good nick, look at the condensor.
Alan

[fierochris]

good battery from my benz ill order a condenser, pionts, and a new rotor.

[T77911S]

the coil does NOT make a spark as soon as the key is turned on. cars without the CD unit did, but not porsche. basic ign systems, switched 12v is applied to one side of the coil and the points are on the other terminal.
on the 911, the CD unit is connected to the terminal where the 12v was applied and the other side of the coil is grounded. the switched 12v is now applied to the CD unit. the points are now connected to the CD unit.
there is no voltage on the points so they dont burn like they use to. the points simlply open and remove gound from the CD telling it to send about 450v ( vs 12v ) to the coil. the coil is a step up transformer of about 100:1 making a 45,000v spark vs 1200v. you really dont need to set the gap on the points, as long as they open and close completly the car will run. porsche saw the importance of a higher voltage back in the 60's. this higher voltage is why we can set our plugs to .050" .060"
if the coil is sparking, check the rotor and cap.
milt,
i too have left the rotor on the bench....more than once.

[RoninLB]

this guy has PMOs.

Maybe he has MSD that toasted a rev limiting rotor ?

[T77911S]

ronin,
has an MSD toasted a rev limiter before? i cant see that happening. my permatune is bad so i was planning on trying an MSD...because of the cost ($170)?

[RoninLB]

I use non-rev limiting VW rotor


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