Strong Start and DEAD. Stranded without spark at coil!!

[911SauCy]

Drove the '78 to work this morning, ran hard and fast, didn't skip a beat.

Just went out to grab some lunch and take the long way back. Car started 100% normal, ran strong for about 20 seconds and just shut-off...like I turned it off. No sputter, no hesitation, just turned off.

I checked fuses, ground strap, plugs, coil wire, wires from alternator, CDI is making noise, cranked it more and all I was getting was a strong eu-de-87-Octane. I pulled the coil wire off and checked for spark (yes, I know it's a no-no) no spark.

I have a hunch as to 2 things it might be other than a bad coil.

Bad relay 911.615.115.00 (found under CDI cover) or possibly the tach limiter wire? The one that would cut the engine when rev limiter is hit, as the car cut out that abruptly.

HELP!!?? THOUGHTS!!??

[wwest]

Disconnect the battery, slow count to 10, restart...

????

[ischmitz]

You can measure the coil pretty easily with a DVM: Disconnect it and measure resistance between the two terminals (~ 1 -2 Ohm) and then measure resistance from one of the terminals to the center HV terminal (1 - 2 kOhm). That will tell you whether its the coil or not.

Next, the trigger signal from the distributor could be missing. This is a common issue when the green coax wire disintegrates due to heat and age. It can internally short. Inspect it for no cracks. Not really easy to measure unless you have access to an oscilloscope.

Next, the CDI box is suspect. If it whines that is not sufficient to tell whether it works. Its the other way round: if it doesn't whine it is bad.

Even when it whines it could be internally short (whine is higher pitch, around 4.5 -5 kHz, than normal, 3,5 kHz) You need a trained ear to be able to tell. Else it could have another defect that prevents it from releasing a spark.

Ingo

[911SauCy]

Will do

[theiceman]

I posted the same as Ingo but it didnt upload for soem reason , he is pretty well dead on .. my troubleshooting is simlter tho..

1. if its a silver brazillian coil .. thats the problem , throw it out ...

disributor pick up and rev limiter are possible but down lower on the list of probabilities ..

if you have a spare pop in another coil . if thats not it find a buddy and swap out the CDI BOX.

just like the phrase all that glitters is not gold .... all that whines is not always working ...

Good Luck .

[911SauCy]

Trigger wire doesn't look all that awesome...

Being that all of these parts are original, coil, trigger wire, cdi...I think I'm simply going to order the 3 and go for a "while you're in there" kind of refresh, instead of fixing one of the issues and chasing more down as they present.

[TheSt|G]

Why are you running 87?

[T77911S]

i would not do that. if anything, i would have the CD rebuilt replacing the old capacitor. as for the dist and coil, what you have is probably better than what is new. go get an MSD coil and just carry a spare coil and if you feel the need, carry a spare CD unit. as for the dist, i think NAPA carries the coil that goes inside but as far as replacing it on the road, that would be a bit of a task. at least you would have the part though.
clean up the wiring and make sure it is not brittle and cracked.

[Bob Kontak]

Originally Posted by TheSt|G

Why are you running 87?

Because he has 8.5:1 compression.

[Bob Kontak]

Originally Posted by T77911S

i would not do that. if anything, i would have the CD rebuilt replacing the old capacitor. as for the dist and coil, what you have is probably better than what is new. go get an MSD coil and just carry a spare coil and if you feel the need, carry a spare CD unit. as for the dist, i think NAPA carries the coil that goes inside but as far as replacing it on the road, that would be a bit of a task. at least you would have the part though.
clean up the wiring and make sure it is not brittle and cracked.

That's a big plus 1.

If you want to throw parts at it, go buy a new $18, 1967 Chevy coil and throw that on.

Next purchase S/B a multimeter.

Green wire is expensive and a PITA as you will need additional connectors. The coil thingie inside the dist is cheap but very easy to test. If you test resistance through that distributor coil (unplug the CDI six pin from the CDI and touch the green core and shield at the connection you have in the picture) it should be in the 575-ish range.

[911SauCy]

New random thought through reading...

Was reading on Perma Tune website. They say that if your coil goes bad, the CD box is destroyed...

True? (Just seems like that would "make sense" for them to say considering they're supplying new boxes.)

I am definitely going to buy a new coil, already got the multimeter.


Also, does the dist need to be removed to replace the trigger wire? Looks awfully close.

[T77911S]

yea, you cant get to the screw on the side to unplug it.

do you have a perma tune?
i prefer MSD. the new MSD has an LED light on the side that flashes when it gets the trigger from the dist. could be a VERY VERY big trouble shooting aide on the side of the road....or at home. MSD also has a dial in rev limiter.

i am not sure of exactly how yours is wired, but from the pic, is that how they did the 78?
looks like someone fab'd something to make it work. (IE, not original).

just as a thought. i wanted to keep my 930 wiring harness original. i had to replace the wires to the coil. instead of cutting the sheething on the harness i was able to pull in new wire using the old wire to pull it. sprayed a little silicon in there to help them slide.


from the pic, that part of the green wire does not look that bad. you may want to splice it there if you need to splice it.

[Bob Kontak]

Originally Posted by 911SauCy

New random thought through reading...

Was reading on Perma Tune website. They say that if your coil goes bad, the CD box is destroyed...

Legacy Permatune boxes do not stand up well against imperfections in your cars electrical system.

On the Permatune site there is a diagram of the six pin connector. Measure the ohms between trigger and shield wire. S/B 575-ish. If so, you can drop the green wire variable.

Also, if Permatune, she may fire up now. If it does, do not hammer on the car. That can beat on the box causing it to quit again on the way home.

[911SauCy]

Originally Posted by T77911S

yea, you cant get to the screw on the side to unplug it.

do you have a perma tune?
i prefer MSD. the new MSD has an LED light on the side that flashes when it gets the trigger from the dist. could be a VERY VERY big trouble shooting aide on the side of the road....or at home. MSD also has a dial in rev limiter.

i am not sure of exactly how yours is wired, but from the pic, is that how they did the 78?
looks like someone fab'd something to make it work. (IE, not original).

I'll try and exercise my sideways flat-head unscrewing capabilities...

No Perma Tune, just reading about options. Just thought it was strange as i check with a few buddies and read a lot on here, nothing eluded to a bad coil wiping out the CD box.

If it comes to needing a new ign, i'll be going with the MSD

There's plenty of "not original" I keep finding. Bought a green wire regardless, as parts prices continue to rise and eventually I'll make it right.

I really just want the car running again, season is coming to a close and I've done less than 600mi this year!

[911SauCy]

Originally Posted by Bob Kontak

Legacy Permatune boxes do not stand up well against imperfections in your cars electrical system.

On the Permatune site there is a diagram of the six pin connector. Measure the ohms between trigger and shield wire. S/B 575-ish. If so, you can drop the green wire variable.

Also, if Permatune, she may fire up now. If it does, do not hammer on the car. That can beat on the box causing it to quit again on the way home.

I found that diagram and am planning on testing tonight.

The car crapped out last Tuesday at work, was towed home DOA last Tuesday night

[Bob Kontak]

Originally Posted by 911SauCy

I found that diagram and am planning on testing tonight.

Just did some searches. Ohms s/b around 600. Thing is, I don't know where the cut-off is.

I would say no resistance or infinite resistance should raise an eyebrow.

Hey, you get what you pay for.

Also, I have never read of the coil pack in the distributor going bad. Your highest risk related to green wire/coil-pack is continuity/ground faults.

[911SauCy]

Originally Posted by Bob Kontak

Also, I have never read of the coil pack in the distributor going bad. Your highest risk related to green wire/coil-pack is continuity/ground faults.

Exactly. One of my "buddies" used to build SBC race engines and had never heard of that either.

He's now a pre-war motorcycle aficionado.

[ischmitz]

I would have the CDI tested rather than buying a replacement. There's a known failure mechanism where it stops working under temperature. And that can be repaired.

Cheers
Ingo

[911SauCy]

Originally Posted by ischmitz

I would have the CDI tested rather than buying a replacement. There's a known failure mechanism where it stops working under temperature. And that can be repaired.

Cheers
Ingo

I was going to go through the hosts repair service if need be.

[boyt911sc]

Originally Posted by 911SauCy

I was going to go through the hosts repair service if need be.

911SauCy,

I work a lot with CIS engines and if I ever need someone to check my CDI, I'll send it to Ingo. Or send it to someone you don't know.

Tony