no spark

[laotsu]

I think the is no spark at the coil wire because i unpluged it from the dizzy and held it to the frame while cranking the motor and saw no spark. I uninstalled working single point dizzy and coil from 1972 521. unistalled working matchbox dizzy and MSD Blaster2 from 1971 521. installed matchbox and Blaster in 1972 truck, np issues. Installed single pint dizzy, coil and ballast resistor in 1971 truck, no spark. I checked the wiring diagram it all seems to jove except for the fact that I think the diagram shows connections for a dual points dizzy. not sure if blue/yellow or black/yello wire should be attached to dizzy, tried both neither helped. engine turns over but wont fire. 

 

 

[DanielC]

obligatory 521 wiring diagram. 

 

This wiring diagram does not have the wiring of for the retarded (alterabled?) set of points used in many USA model 521 trucks. 

 

The black with yellow wire is the normal or advances set of points.  Use that with a single point distributor.

 

Almost every ignition system works the same way.  There is a coil, and some type of a switch controlled by the engine, or a computer.  The switch grounds the coil, that has power applied to it.   The points, or matchbox, or some ignition module controlled by the computer, opens the switch when the spark is supposed to happen.

 

Check for power at coil positive.  if you have power there, you should have some power at the black with yellow stripe wire.  This is power that has gone through the coil, and ballast resistor, so do not expect a full 12 volts.  Grounding this wire, and then ungrounding it should make the coil fire.   If it does, about the only thing left is the distributor.  Its job is to ground that wire, and when the time is right, unground the wire, and make a spark.  Oh, yea, the cap and rotor send the spark energy to the correct spark plug.

[laotsu]

Test light lights up on positive and negative of coil. Is that how it's supposed to be?

[datzenmike]

Yes. Probably brighter on the + side. Crank the engine over and it should go on and off, IF... the points are closing properly.

[dr.feltersnatch]

the positive side of the coil should be switched power. the negative side should be fed from the points. 

[DanielC]

If points are open, or not making contact, the test light on negative side of coil will stay on. 

[laotsu]

I had it wired for dual points. I have spark but battery is too weak to fire it.

[DanielC]

What do you mean you had it wired for dual points?  The stock Datsun system only used the retarded set of points, in third gear, part throttle, clutch pedal fully out.  if you have a weber carb, or a five speed transmission, you are missing parts to make the stock Datsun system work.

 

Some American V-8 engine used dual points to increase the dwell time. this is not needed on a Datsun four cylinder engine, because even though a Datsun engine runs higher RPM, it still is not firing as often as a V-8.  

[laotsu]

CA 521s came with dual points. that's what I have and thre wiring diagram I was looking at. it is slightly different thatn the one you pisted.

[DanielC]

Oregon 521 trucks had dual point distributors too.  All the details are in this manual

 

Like I said, the retarded set of points in only used in third gear part throttle.  Essentially what happens is this. In third gear, if all the other conditions are met, a relay closes, and that puts the second set of points in parallel with the first set.  This set of points is retarded, that is it closes 5 distributor degrees, and opens 5 distributor later than the first set of points. 

 

Do you have power on the black with yellow stripe wire, when it is unplugged from the distributor. with the key on?

If yes, the only thing left is this.   Do the points in the distributor close, and do they make good contact?  With the black with yellow stripe wire disconnected, the terminal on the distributor is connects to should show 0 ohms between it and ground.

 

It is very common for the points to get a piece of dirt in them, and not make contact.

Another possibility is a bad condenser.  If it is shorted, no spark, and if it is totally open, again no spark.

[banzai510(hainz)]

if you have power to the ballast which goes to the + side coil. key ON

there will be 2 wires in 1 lug at the +side.  one come drom the other end ballast resisitor the other is the HOT start.

 

 

you don't even have to use the supllied color wires, just make a wire from the dizzy where the bigger condenser is(main points) and this will go to the - side coil.

 

 

The coil + and minus side is more or less close to same that why you have the test light come on or close to 12volts. its just a loop of wire.

[laotsu]

this issue has been resolved I had the truck wired according to a dual points wiring diagram and am running a single points dizzy.