new cdi bosch, new msd coil, no spark
 

Hi everybody. Today i pass all te afternoon with some friends trying to restore the car ignition to a used bosch cdi, but after setting all the cables again with the proper electrical wirings, i have no spark.

the bosch cdi works (i think), makes the whistling sound :)

Tried the telegraphic test, with a spark grounded and i have spark.

Then tried to see a spark when cranking, and a spark plug connected to the center coil cable, and NO spark.

Also tried to get a spark from a spark plugs with a spare spark, and when cranking, NO spark either.

Tried with a second rotor and nothing either.

The connections from the cdi are ok, all new cables. "B" have 12v ," A" new cable to 15 coil connector, "c" new cable to distributor. "D" new cable to ground.

I am stuck with no fire and no running car :(

Any advice??

Thanks!!

Hi,

If the telegraph test works, this means that your coil and CDI are communicating. I woiuld think that since no spark when cranking, your poits are incorrectly adjusted. You can chack this by removing the distributor cap and watchinghte points as someone cranks hte car. They will open a close. If not, adjust so they do.

Also, check the condition of the distributor cap and rotor. Rotor should have some resistance between the center of the electrode and the tip...NOT an "open circuit" (over 10K ohms).

Checked the points moving the engine manually from the pulley and it opens and close. Also tried moving the car with 2nd gear in, and it also open and close also.

The rotors are ok with some resistance over the ends.

The cap seemes to be perfect no crack or moisture on it.

I think the problem comes from the new cable i installed coming from the distributor to "C" connection on the cdi or something related to it. But its wired because i have spark when i make the manual telegraphic test.
The msd coil is new.

forgot to add, i am not using the original ignition harnesses because they where taken out from the car, could this be a problem???

if it's a problem, where can i get a good CDI 3-pin used harness to re attach to my car??

I'd probably pull the coil wire from the distributor and set it up to test for spark to a ground first. Then turn engine clockwise manually the way it's supposed to turn till points are closed. Then turn ignition on and reach into the points arm with a screwdriver to open and close the points. When you open the points you should have spark. Then try turning key to "start" to open and close points while checking coil spark.

if you have spark both times you'll have a direction to search for a solution

Refresh my memory how you do the "telegraphic test".

In general the Bosch 3pin CDI releases a spark every time you ground pin C. The wire to the distributor does the same thing: Every time the points inside the distributor close they ground the wire that runs to pin C of the CDI box. And that makes the box generate a spark.

To troubeshoot you need to check if the points close, and if the wire from the points to the CDI box shows continuity to GND when the points are closed.

Next connect a spare spark plug with a high-tension wire straight to the coil. This removes the rotor and cap from the equation. Once the points close it should produce a spark. You can jam a small screwdriver into the points to test. Then turn the engine over.

Once you have gotten to the point where a turning distributor produces sparks with a single spark plug connected to the coil you can add the distributor to the equation.

Ingo

no info on Bosch CD box from me except that it's a great unit that should have spark plugs gapped to factory spec

spark happens when you open the points

Is the CDI box the one for points or magnetic pickup...?

A stock '73 car has a 3-pin CDI box and it expects a points signal. The later 3.0 had the 6-pin CDI boxes for magnetic pickup.

Ok, new tests all the afternoon.

Results:
- batteries fully charged.
- whistling sound coming from cdi
- tried telegraphic test method 1: spark connected to HT cable, grounded, and with distributor cable coming from CDI disconnected, have spark when i tocuh the dizzy as ground every time, powerfull blue spark.
- tried telegraphic test method 2: same procedure but moving the points with a screwdriver with ignition ON and also have spark on the slave spark plug.

Then:
-tried to get spark when cranking directly from HT cable from the coil, to same slave spark plug and NO spark
- tried with dizzy assembled and rotor, and no spark from a grounded slave spark plug, and NO spark either.

I suspect a problem with the cable from distributor to CDI, or something around there.

Thankssss

Sounds like good troubleshooting, check that wire from the dissy to the CDI box for continuity

james, the cable is a new one black cable i bought 2 days ago. it's a 1.5mm cooper regular cable, should it be some kind of special cable??

thanks!

I wonder if it should be a spiral wound one like the cables to the spark plugs. High voltage, short-duration electrical pulses need that sort of cable.

If it's points, it's just a wire, make sure you have good continunity between the points (the nut that has the wire on it with the points open) and the blade on the plug (on the 3-pin plug).

good slow progress above

if my problem I'd now hook up an old style analog volt meter to the CD box red wire and test voltage
- with key "on"
- with key "on" and doing the points/screwdriver test
- while cranking the engine and testing for spark

if voltage looked good on every test, especially while cranking, I'd next disconnect the tachometer and try another test for spark while cranking the engine

i sure hope he did the routine stuff

i figure he did

we'll see

This means that when your CDI box gets a signal, it will make a spark. Good.

This means that when the points move (open/shut), your CDI gets the singal and makes a spark. Good.

I assume you mean: the points are connected to the CDI box and you have a spark plug attached to the center lead of the coil. You then crank the engine and no spark.

This means that points are not opening and closing properly. Check your gap. and watch your points as you crank the car, they need to fully close and open. A way to test this is to get an ohm meter and connect it across the points (one lead grounded and one lead to the connector you use to connect the CDI to the points (disconnect the CDI from the point so you do not mess up you ohmmeter). When you crank the car, you will see the ohm meter bounce as the dizzy rotates. Please report your findings.

If the test above does not work, neither will this one.

I think you have a problem with your gap.

Keep at it. Electrical problems require patience and attention to detail to solve.

well, i have just come back from working with the car, with some great news :)

Finally the problem was, the points. They where closing and opening, but somehow didn't work right, so i installed the petronix system i bought on my last trip to USA, and guess what?

Started like a champ! :D

there was a lot of old fuel round there, so i ran the car some minutes to clean it all the possible, with a liquy moly injection reinginier and some new fresh fuel.

I am very happy so far with the petronix the installation was very easy, and got it working very fast.

But i have one question about the dizzy.

I removed it at TDC and rotor pointing Cyl 1.

But after installed the petronix, i have to rotate the dizzy all the way right, to get the right timing.

Did i miss anything, or maybe the petronix is bad installed, or don't know if i installed the dizzy one notch further, and that's why it is at the end of the "timing adjustable area"?

thanksss alottt for the helpppp

You can re-index the distributor 1 tooth to put you back in the range of adjustment. Glad you got the car running. :)