no spark

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my 70 stang 250l6 cranks over but doesnt start there is no spark what can be cause this? help!!
 
Check for voltage to the "+" or "BAT" post of the coil with the key in the "On" and "Start" positions. If there is, check coil and points. I'd go ahead and change them if they'r old.
If there's voltage at "On" but not at "Start," try hooking a wire from the red battery post to the "+" post of the coil, and crank it. If it starts, you may have a back ignition switch or ballast resistor.
If there isn't voltage to the coil on either setting, check for voltage to the ignition switch. If there is, you probably have a bad switch.
That's a good starting point. :wink:
 
The coil needs voltage that it gets from the starter relay (solenoid). It comes from the small top post nearest the starters wire, when turning the engine over. The voltage next comes from the ignition switch through a resistive wire or ballast resistor after you get it to fire up. Then the coil needs the switched ground from the points. Burnt points would prevent a spark. A shorted condenser would prevent a spark also. An open coil would prevent spark. After that, your into the high voltage side of things. Coil wire, cap, rotor, plug wires, and plugs.
 
i have petronix ignition system the coil is getting 11.5v ichecked the coil resistance i gettin 1.5 ohms you think the ignition switch is bad?
 
our jetta has the exact same problem...it just up and died and we get no spark...new coil...still no spark...thinking mabe the key in the timing gears or something gotshot cause there aint no compression either...whatever the P.O.S is being sold to a friend for 100 bucks....
 
I've messed with too many motors. And guess what? Today I put the plug leads one position retarded on a SAAB 4-potter. :oops: My point is that sometimes the subtle things right there in our faces don't appear when we'd really like them to. Triple check everything, take a break (get away from those fumes), and come back to it. Check it all again. Check your base timing. Check your plug leads and order. Unhook the fuel line at the carb and crank the motor, see if the fuel squirts out (be prepared, of course, to catch it).

Near enough to 12V at the coil: Check the wiring to the Ptx. If that's OK, crank the car shorting the coil centre lead to ground. Look for a spark. If you've got one, the problem is the cap/rotor/plug wires. If no spark, you need to check the HT side of the coil to ground, too. From memory, 6-8K ohms is pretty typical (my meter's dead right now so can't check).

Let us know if you're still stuck, after trying these things.

Cheers, Adam.
 
Since you have the Pertronix, then you can easily put a set of points in , and check again. I Have the Pertronix I, but I carry a set of points, just in case. :wink:
 
what do you mean to check the hot side of coil to ground i put new cap rotor an dplug wires still no spark. are sopposed to have voltage on both sides of the coil. help.. :cry:
 
8) whne you have the key on you should have battery voltage at both coil posts. if not you have a bad coil.
 
Are you saying that your car will not turn over? If that's what you mean, then also check your carburetors choke. If it doesn't open when you crank the engine then the car will never turn over (no air to mix with the fuel).

This happened to me. I was getting spark all the way to the tip of the plugs and I was 100% sure that my timing was right. Well, all was correct but the choke. :roll: :wink: :D


-Chris
 
my car cranks over,carb is good just not getting any spark, i have voltage at the coil but none at the wires. put new wires cap rotor still nothing what can it be????
 
I will start by discussing an ignition that uses breaker points. When the key is on, voltage is present at the primary winding of the coil. When the points close, current flows from ground, through the points and primary windings to the battery. This causes an electro-magnetic field to build up in the coil until it reaches the point of saturation. When the points open, the flow of current is interupted, causing the field to collapse, which induces a voltage in the secondary windings, which builds up until it is high enough to jump the gap, causing current to flow (spark). Now, back to the beginning. When the key is on (points open), you can use a voltmeter or test light to indicate that voltage is present at BOTH primary terminals of the coil. But when the points close, there is effectively NO voltage to be measured at the negative (distributor side) of the coil. This is because that terminal is at ground potential as long as the points are closed. If you put a test light on the negative terminal while cranking, you should observe the light flashing on and off as the points open and close. If the light stays on all of the time, there is no contact through the points to ground. A Pertronix just uses a solid state switch to replace the points. For the coil to work, it must be alternately connected to ground and disconnected (points closing and opening) Yup, it does this real fast :shock:
Joe
 
Take out the Pertronix; put the points back in. If that's not the problem, you at least have a set of points for when it fails.
 
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