Power and whine at cd unit but no spark

[tassie targa 76]

G,day all.

I have a 76 2.7 that has had a hard life before me.

The car has been completely stripped over the last couple of years and now is back together. It was running before pull down only changes new plugs, distributor cap, rotor 6500 limiter type and

I have almost completely rebuilt the engine harness except for the 2 wires from the CD unit to the distributor and the coil. Mostly because it was in a very bad way and I'm not sure the electrical connectors to the cold start, WRU ext were all connected they are now

Today hooked up a battery fuel system working.

Cd unit has a high pitched wine and I have checked all connections and continuities.

I have power at the B terminal of the cd unit but no spark at the plugs or from the coil output.

I have checked that the A terminal from the CD unit goes to the points, C terminal goes to the coil, the other side of the coil is earthed and also goes back to the earth of the CD unit. The shielding around the wire is also earthed.

I have checked the resistance across the coil at both primary and secondary the secondary .9 ohms but I have a bit of trouble reading the primary resistance the multi meter set to 20000 was reading 900 I think a bit more the the expected 650 to 750


I have a timing light a multi meter and a 12 v test light

Is there a way that a home mechanic can check a cd unit or any other advise or opinions greatly excepted





Please help

Regards Michael

[timmy2]

Have you cleaned the points?
They can tarnish up when sitting for a while. Gap set correctly ?
Checked them to see they are opening and closing correctly? Checked continuity of the wires to the coil and dizzy from the CDI unit?
There was a good thread recently discussing the testing methods for a 3 pin CDI.

[timmy2]

Plug wires oriented correctly?
Been there done that.
New rotor faulty?
Plug wires fully seated?
Think about what you have changed, it was running before you swapped out components.

[tassie targa 76]

Have checked all continuity and point gap all ok , plug leads and plugs all ok

Not getting any spark from the coil lead

Would it be fair to say that if the cd is whining then it ok?

Spent about 4 hours double checking everything I could

Do cd units fail just by sitting around for a couple of years

I pretty confident that the wiring is all ok so I guess it's either the cd unit or the coil.

[zelrik911]

Just throwing a few ideas out there!
IF the CDI whistles, I would suspect the coil - is it the right one & could you test it on another car? Are the wires to the terminals swapped?
Does the tacho needle move at all when cranking ( which might indicate a short somewhere). Do you have a "co ax" green wire on yours, as these break down a lot & the connectors into the distributor can also short.

On other Bosch equipped cars, I have experienced the rotor button metal burning out under the glue between the centre and the tip.

Looks like you are very close to running anyway - so good luck with it
Peter Melb.

[tassie targa 76]

G day Peter

Mine has 2 white coax type wires no blue or green

The 2 white wires come from the CD unit to the distributor at the points and the other to the coil I have double checked their orientation and continuity.

They are old and stiff but seem ok they are the original ones that were in the car prior to pull down.

I have checked the price of a new coil and I can buy a new msd and coil for about the same price (not in aus way to expensive)

I guess at least then I have new components from power to plug except leads
Regards Michael

[Flojo]

your cables look crappy, torn... maybe one of them even broken?
what about the famous "green" wire, that connects the CDI with the dizzy head?

[Bill Douglas]

Ah oh, the high pitched whine of death.

As Flo suggested fix up the wires in case the current is leaking out somewhere and make sure your connectors are making good metal to metal contact.

Good luck.

[gamin]

Might that be the infamous (pos) Bosch silver coil in the picture? If so, it may be the source of your problems.

[HarryD]

Check post #9: Troubleshooting ignition problems, but it's all Greek to me.

It may contain the tests you need to narrow down the problem.

[mysocal911]

Originally Posted by gamin

Might that be the infamous (pos) Bosch silver coil in the picture? If so, it may be the source of your problems.

Buy a cheap ($20-$30) VW coil at an auto parts store for just testing.
Place the coil wire going to the distributor about 10-12mm from the alternator's
metal housing while cranking. Also use a test light to make sure the points
are opening and closing properly.

[T77911S]

if you are goning to get a coil, get the MSD.
your wires dont look that great. any wires that have the ground braid, ohm the center conductor to the braid and ground, wires that dont, ohm to ground.

just because the CD whines does not mean it is good, just means half of it is working. the large cap in there can go bad but you can check it.

open the back of the CD unit. (i am doing this from a pic, i hope yours is the same). look at the center pin on the 3 pin connector to the CD. follow that straight across the circuit board.
you will see to componets next to the coil, they are in line with each other. those are diodes. go to the end of the second one. set you meter to Ohms, probabbly a hi scale. put one lead on the far end of the second diode and one lead on pin A of the CD. the meter SHOULD start counting up or down. switch leads. it should now count the other direction. you can alsoo take a wire and short those 2 points together, then connect you meter bac k and it should count UP. that is the capacitor charging up from the battery in the metter. if it does this, the cap is good, cant remember if the caps usually short or open, but if the meter reads eirther way or just sits there, the cap is bad.
post pics of what you are doing if you need help.

you can just buy the coil and have a spare if that isnot the problem

[mysocal911]

Originally Posted by T77911S

if you are goning to get a coil, get the MSD.
your wires dont look that great. any wires that have the ground braid, ohm the center conductor to the braid and ground, wires that dont, ohm to ground.

just because the CD whines does not mean it is good, just means half of it is working. the large cap in there can go bad but you can check it.

open the back of the CD unit. (i am doing this from a pic, i hope yours is the same). look at the center pin on the 3 pin connector to the CD. follow that straight across the circuit board.
you will see to componets next to the coil, they are in line with each other. those are diodes. go to the end of the second one. set you meter to Ohms, probabbly a hi scale. put one lead on the far end of the second diode and one lead on pin A of the CD. the meter SHOULD start counting up or down. switch leads. it should now count the other direction. you can alsoo take a wire and short those 2 points together, then connect you meter bac k and it should count UP. that is the capacitor charging up from the battery in the metter. if it does this, the cap is good, cant remember if the caps usually short or open, but if the meter reads eirther way or just sits there, the cap is bad.
post pics of what you are doing if you need help.

you can just buy the coil and have a spare if that isnot the problem

The test mentioned above is one of many tests that will indicate whether the CDI has
a problem or not.

[timmy2]

Bosch silver coil.... Very likely...
New rev limiter rotor, possibly opening early (or always). Try it with a non limiting rotor first.

[zelrik911]

Any developments?
Re coils; some old M Benzs (late 60's to early 70's with points ignition) have coils with the same Bosch part number: Bosch # 0 221 122 001
- they are marked "730" and "KW 12 V (yours is "460"?) It might be easier to find a MB test coil at the wreckers for next to nothing. Might even be on that era Volvo's too.

I may have one in my box of old bits if you cant find anything local

If you want to go MSD, there is a basic version called Streetfire (about $200) which a Melb. Forum member (Racetech) got for his Targa restoration & it seems to go real well.

[ischmitz]

Whining noise of the CDI indicates you are getting power (+12V and GND) to the box. Depending on the pitch it is either an internal short or the DC/DC is working normally and something else is amiss.

If the whine is higher-pitched that indicates an internal short in the CDI box where the DC/DC converter is shorted to GND and thus is frequency shifts more towards 4.5kHz range. If you remember how a normal box sounds in stand-by you can immediately.

If the whine is around 3 - 3.5 kHz that is normal - you either have no adequate trigger signal (wires, points) or a defect in the internal pulse shaping and trigger circuitry. In very rare occasions something else internally is wrong.

Ingo

[dicklague]

You can take the points input into the CDI and short it to ground in a tapping motion to simulate the points.

Hook up something like this on the other end:



you should have spark. if not you know it is the CDI or the coil

[tassie targa 76]

Hope to get back to the car in the next few days and will try a few of the tests

Regards Michael

[tassie targa 76]

Thanks to all for advice and offers of assistance but after more inspection there is a blown circuit that can be seen with the back off the unit.

I have a msd street fire unit and coil on the way $211 aus dollars delivered from amazon.com

My dad rigged an old coil and condenser from stuff in his shed and by passed the cd unit and the car started I guess that sorts out most things, like points, leads, power, timing ect.
So new unit should be here next week, takes a while to get stuff to Tassie from USA

But pretty sure we have it sorted now

Regards Michael

[304065]

Originally Posted by tassie targa 76

Thanks to all for advice and offers of assistance but after more inspection there is a blown circuit that can be seen with the back off the unit.

I have a msd street fire unit and coil on the way $211 aus dollars delivered from amazon.com

My dad rigged an old coil and condenser from stuff in his shed and by passed the cd unit and the car started I guess that sorts out most things, like points, leads, power, timing ect.
So new unit should be here next week, takes a while to get stuff to Tassie from USA

But pretty sure we have it sorted now

Regards Michael

Bad Brazilian coil.

FYI you should never use an early vw or mb coil designed for Kettering ignition, the primary resistance and inductance are way too high for cdi. It might work ok but ignition power will be way down and the cdi box is not designed for it. Use a used German black 001, they are out there

No coax on a stock 76 that is not till 6 pin sc box 78-