911 sc no spark
 

Please help, my 1981 SC will not make a spark .
It has the original ignition system with Bosh CDI unit and the black case Bosh coil.
The CDI unit makes the right noise with the ignition on and I have power at terminal 15 in the six pin plug.
I would like some one who has expert knowledge to kindly put together a procedure to test the various components.
I have had the car for many years and have done quite a lot of work to it but none on the ignition system, I am reasonably handy with a multi-meter.
The car was idling in the garage and just stopped. No spark at plugs.
Thanks !

how about using a search to look for your problem instead of asking someone to put a procedure together for you in your first post. We are more willing to help people who try to help themselves.

This could be the green wire problem. I had this on my 1978SC recently and I think it had been going for some time. The green wire goes from the distributor to a connector in the wiring harness; it's only a few inches long. If you have the Bently manual follow the instructions for checking on page 280-9. You are looking for a pulse from the distributor using your meter with the engine cranking. If you don't have an assistant to crank the engine you can remove the distributor and do it on the bench by rotating the rotor by hand while checking for a pulse. Make sure you set the crankshaft pulley to TDC with the rotor pointing to No. 1 plug as per the manual before removing the distributor

Thanks for the advise,
I am new to the Forum and mast apologize for my lack of forum skills.
I tried for hrs to bring up relevant posts by entering appropriate key words in the search box Things such as " 911 sc no spark" or "911 sc ignition trouble shooting"
etc but the result only showed a lot of unrelated posts... What am I doing wrong ?
I would really appreciate somebody setting me straight
Thanks

Thanks very much for the advise I have checked this as per procedure and checked ok.
I am new to the Forum and must apologize for my lack of forum skills.
I tried for hrs to bring up relevant posts by entering appropriate key words in the search box Things such as " 911 sc no spark" or "911 sc ignition trouble shooting"
etc but the result only showed a lot of unrelated posts... What am I doing wrong ?
I would really appreciate somebody setting me straight
Thanks

you can check the coil with a MM.
primary should be around .1ohm, a short.
secondary should be around 500 ohms.
based on my 930 coil.
check primary to secondary. resistance should be hi

if that is good it is probably the CD unit.

Definitely manipulate the green distributor wire. And, just because you can hear the unit sqealing does not mean it can fire the coil. If you need the unit serviced, check pelican part number 'AT-CDI repair'.

Try pushing the coil wire ends into the distributor and coil. I have had my coil wire back out on the distributor. Sounds to simple but it happens.....

Yeah, the search function here is crap. No worries.

Do you have a spark tester ?

Test for spark at the coil. Pull the coil to dizzy wire. Bend the wire back and try to position it where it is secure against the side of the coil and make a slight gap to one of the coil mounting bracket studs. Have a helper crank the car and watch for spark. No spark, coil or CDI is bad. Orange spark, spark is weak and won’t ignite the air/fuel in the cylinder.

If spark is good (blue/white), problem is between the coil and the cylinder. Bad cap, rotor, plug wires or plugs.

I’d get another coil. It’s cheap and, worst case, you have a spare coil. (Caution: I did have an MSD coil that was brand new turn out to be bad right out of the box so it does happen. Quality isn’t what it used to be.)

Thanks tirwin and everyone else its great to get some help !
So I have pulled the wire from the dizzy and bent it back to the coil and held it with insulated grips at a slight gap from one of the coil mounting studs as you suggested, and still no spark. I have purchased a new coil so now I have 2 and as you say always good to have a spare, did the test with both so unlikely to be the coil. what do you suggest the next step should be?
Once again thanks !

Hi pmax, yes I have a spark tester, it has a light that lights up if spark is Ok and it connects in line between the top of the spark plug and the leed .

OK, yes, try swapping the coil with a spare and test your current one as TT suggested. Good to have a spare one anyway.

Thanks every one especially pmax and tirwin .
Here is what I found so far, it would be good if someone could help me make some sense of it.
So I did the test as Tirwin suggested by disconnecting the wire from the dizzy and holding it (with insulated grips) at a slight gap from one of the coil hold down studs, no spark. So I got a new coil ( the proper one) and still no spark.
I also tested for voltage at the positive and negative wires at the coil and have no voltage with ignition on or engine cranking ! ( I thought I had voltage here before but old age must be catching up )
So I went back and disconnected the six pin plug at the bottom of the CDI unit and checked for power at terminal 15 with ignition on and have12.6 volts as I should .
(The other thing I noticed is that terminal A which, according to the Bentley manual, supplies power to the Coil from the CDI unit has continuity to ground when connected the coil, this may be normal as there is little resistance between negative and positive contacts on the coil , this may be normal as there is little resistance between negative and positive contacts on the coil .
So have I got a bad CDI unit, two bad coils or what else could it be ?
once again thanks for listening !

Thanks every one, especially pmax and tirwin .
Here is what I found so far, it would be good if someone could help me make some sense of it. I did the test as Tirwin suggested by disconnecting the wire from the dizzy and holding it (with insulated grips) at a slight gap from one of the coil hold down studs, no spark. So I got a new coil ( a proper one) and still no spark.
I also tested again for voltage at the positive and negative wires at the coil and have no voltage with ignition on or engine cranking ! ( I thought I had voltage here before but old age must be catching up )
So I went back and disconnected the six pin plug at the bottom of the CDI unit and checked for power at terminal 15 with ignition on and have12.6 volts as I should .
Terminal A that supplies power to the coil has continuity.
When I test for a pulse as per the Bentley manual across terminal 7 and 31d I get an reading with my meter on VAC fluctuating between 1.630 and 1.650 I am not sure if this is a pulse or not.
Can any one draw any conclusions from the above ? Once again Thanks !

If you want useful search results, use this link.

https://cse.google.com/cse/publicurl?cx=014238775269149376701:ojolaky8hjg

(unfortunately the auto-emoji generator insists on turning colon o into :o!)

thanks rdm , i have tried to post an other two replies and a post in answer to others in the last two days, but i am getting a message saying that my posts will not appear until they are checked by a forum monitor but nothing has happened yet.
Do u know whats going on ?

""Thank you for posting! Your post will not be visible until a moderator has approved it for posting. "

I have been getting the above for the last 3 days and none of my posts have been posted , is this normal ?

it seems to be happening with the longer ones even if they are within word number limits.

OK it is normal for posts to take a while before they get posted, must apologize again,
will eventually learn how this forum works.