76 930 No Spark

[kupcar]

I’m having an issue with a no spark condition on my 76. On a afternoon drive, the car basically was running great then while cruising at a steady 3500rpm the car shut off. Almost like the key was turned to the off position. Anyway, I tested for spark and nothing. I’ve done the forum search and I’m familiar with some of the possible things it could be. Unfortunately, electrical isn’t my strong suit. I have been methodically going through the various tests. This is what I know so far. The battery is good and I’ve cleaned the ground to the body. My fuses in the front panel are good and I cleaned the terminals. I do have power to the rear engine panel. I may have an issue with the delayed ignition cutoff relay. I do have power going into the relay(orange wire) but doesn’t seem to go to the CDI Box. I’ve been told to jump the relay. Did that in a test. Power goes to CDI box pin, so the box gets power. Still no spark. The box has been tested and verified good. The coil is new. What’s left, the distributor wire that connects to the CDI box? From what I’ve read the 76 has a clockwise rotating distributor and I need a different wire than the typical green replacement. Part number 930.602.911.00. Anyone have any suggestions or ideas? I’m getting better with my multimeter! How do a test the distributor wire? Continuity? Is there a trick for removal? I also took a picture of the delayed ignition cutoff relay. There is one spayed connector open and a round pin open as well. Is this correct? I also found a brown wire that is screwed into panel for what looks like some sort of ground. Maybe for the engine lid light or defrost ground? Just want to make sure it didn’t belong on the other spayed connector. Thanks for the help in advance. Oh, the car does crank, and all the electrical accessories function.

[356911930]

The CDI box can test good when cold. When a CDI box starts to go bad it usually shuts off after it warms up. You can take a bag of ice with you on your drive and when it shuts off you can put the ice on the CDI box and see if it recovers faster. I have heard that the early eight pin CDI boxes are stronger and usually do not fail as readily as the six and three pin boxes so your problem could be elsewhere.

Rahl

[kupcar]

Thanks Rahl. I’ve heard that as well. This is a 8 pin Permatune that I believe was installed by the previous owner many years ago. I thought that was my issue and that it was time for a new box. Not the case. The unit has been tested and has been verified as a good working box. It’s something else. I’m sure someone has had a similar issue. Wish I was better at diagnosing electrical wiring issues, but I’m learning fast.

[JSV798]

Six months ago my '78SC refused to start. So first confirmed no spark by using a spark plug resting on the engine. Then followed CDI checking procedure in Bently Manual; photo of relevant page:

PHOTO DIDN'T COPY. so see my contribution to this thread:

1978 SC won't start



My understanding of spark generation on this car is as follows: the distributor generates a small voltage pulse which you can check by following above. The CDI transforms this to 400 volts which is then relayed to the coil which ups it to 20,000 volts. There could be a problem anywhere on this route. For example there is a connector to the green wire behind the distributor so you can also check there for the pulse if you don't get it at the CDI end of the cable. In my case it was the green wire: Bentley suggests distributor is faulty in absence of pulse but in my case it was the green wire, confirmed by pulling the distributor and bench testing: distributor gave a pulse when rotated by hand.

Roy

[kupcar]

Ok, I have finally come back to this project. I actually don’t have any measurable voltage going to the cd box. No voltage to any of the 8 pins with the ignition switched turned to run position and during cranking. Where do I go from here? All the fuses up front look fine. Where does the power for the cd originate? Much thanks.

[john walker's workshop]

You said there was power to the delay relay, so pull it's plug off and make a jumper wire that bridges the two terminals in the plug that would be next to the little tube on the relay. Should get power to the CD then.

[RarlyL8]

Relays are notorious on these cars. If no power when jumping the relay move back to the ignition switch, they also are notorious for wearing out.

[kupcar]

Everyone, thanks for you patience and advice. I jumped the hot lead that was going into the delayed ignition cutoff relay to the red and white wire on the above pin. This gave me power to the 8 pin plug. Connected the cd box and gave it a crank, spark!!! Thanks John. Now what does that tell me? Do I have a ignition switch that has failed? Thanks for all the help. I’m learning as I go!

[john walker's workshop]

Dead delay relay. You would have had power to the relay or the jumper would not have worked.

[kupcar]

John, I thought that maybe that was the case last time I was working on this and I bought a replacement from our host. Hooked the new relay up and no spark. I’m happy to see spark but confused why I only get voltage to the cd box pin when I jump the relay. Jumping it gives me constant voltage to the cd box. Key off or on. That seems wrong. Hmm.

[spoke]

I've had 2 issues with spark on my '86 930 with Permatune.

First was the DME relay. I think that's the relay mentioned above. Jump the relay and the engine would run. Popped the lid on the relay to find a relay mounted on a PCB. Took that relay off and opened it up. The relay would work but the contacts had bent over time and would almost make contact. Thus the engine would start, then die, or not start at all. Bent the contacts and cleaned them and never had an issue.

Second one was broken insulation on the green wire to the distributor. This 2 wire interface comes from an inductive pickup in the distributor. I tested this by putting an ohm meter on the 2 wires at the Permatune and moved the wires around. The resistance went from a couple hundred ohms to zero. Below is a picture of the broken insulation. I bought a new wire and in the meantime got the wires separated and cleaned and applied JB Weld to hold them steady. Been running this for 6 months now until I replace the wire.

[kupcar]

Spoke, My green wire tests good for continuity. So that’s a plus. Green wire good, new coil, and cd box checks out. I’m not getting power to cd box unless I jump the ignition delay cutoff relay from the back fuse panel. Replaced the relay with a new one from our host. Still won’t work. Why don’t I have switched power to the cd box. Anyone have any ideas? Fuses were cleaned up front as well as the grounds.

[spoke]

I can only go by the schematics for the '86 930 as those are the only ones I have. The power to the CDI goes through the relay CONTACTS of the Delayed Action Relay directly from the alternator B+ wire. The Delayed Action Relay is turned on by the ignition key. Thus 2 sources of power to the Delayed Action Relay must be present.

Power for the CDI via the contacts of the Delayed Action Relay go between the L pin (to the CDI) and the 30 pin (from the B+ wire on the alternator; also connected directly to the battery). Jumping these provides direct power to the CDI.

Power to the CDI to operate the relay of the CDI comes through the S pin on the Delayed Action Relay from the ignition key. Do you have 12V on pin S of the Delayed Action Relay?

If there is no power (+12V) on the S pin on the CDI, it could point to an ignition switch issue. This is pin 15 of the ignition switch. Pin 15 of the ignition switch also powers fuses 7 and 8 of the fuse box 1. So (again, on the '86 930), fuses 7 and 8 should have 12V on them with the ignition switch in the on or start position.

Pin 15 of the '86 930 ignition switch also powers the sunroof. If you have a sunroof, does it operate?

Pin 15 of the '86 930 ignition switch also powers through Fuse 7 of fuse box 1 the rear window wiper, the horn, and the windshield wipers. Do these work?

Also, do you have a schematic for the '76 930?

[kupcar]

Spoke, thanks for the information. It will come in helpful. If I remember correctly, I don’t have any voltage to the S pin on the relay and 12.8 volts to pin 30. I will have to check fuses 7&8 for voltage with the ignition switch in the run position. I’ll also check power to the wipers and horn. It’s a non sunroof car, so no test there.
Unfortunately I don’t have a wiring schematic for the 76 930. I’m sure it would be helpful even with my electrical deficiencies. I’ve been looking online. Is the best source the 2 volume factory manuals or are there other alternatives? Thanks again to everyone for their time and help.

[356911930]

Kupcar,

I think I have a wiring diagram. Send me a PM with your e-mail address and I will send it to you. 13 meg so it may not send but I can try.


Rahl

[kupcar]

Ok, I back to playing with this problem. It’s been almost a year! Obviously not high on the priority list. I thought for sure it was an ignition switch issue. Installed a new factory switch, still no power to the cd box!!!
I’ve cleaned my grounds, cleaned and checked fuses, had the cd box tested and replaced the coil. I also replaced the delayed ignition cutoff relay. I’m not getting switched power to the box. Does anyone know where switched power to the cd box comes from? From starter?
It’s time to get this thing on the road. Summer is too short. Thanks in advance.

[spoke]

The only way I know of to fix this voltage issue to the CDI is to do a methodical debug using the schematic for your year car.

To state the obvious you have voltage at the battery but not at the CDI so you need to test for voltage starting at the battery and ending up at the CDI. The schematic is absolutely necessary to do this debug. Follow the wires/fuses/switches/relays starting at the battery and ending up at the CDI. Once you have the schematic someone here can help you read the schematic to find the next place to test.

[kupcar]

Thanks Spoke. I bought a wiring diagram specific to the 76 930 but I’m having difficulties tracing the wires. It’s not a factory diagram and maybe it’s not as detailed. I’ll keep trying to decipher things. I’m thinking it’s somewhere down line from the ignition switch. Wish I was better with the electrical portion of the car.

[spoke]

If you have any questions understanding the wire diagram, take a picture of the area of the schematic and post it here or send me a PM and I'll give you my email address. The schematic/wire diagram is nothing more than a roadmap of your car's electrical system. It's easy to get confused by all the wires and symbols but it is essential to solving these kinds of issues.