Igintion Troubles CD box no noise??
 

'76 911S
random backfire/misfire progessively worse as engine gets warmer and goes away aparently when I stick my foot in it.
replaced the plugs wires coil points dist cap. all with new. no improvement.

duh..Hey I found a Tech article here that said to check the CD box first to see if it makes "the noise"

It makes zero noise. Key on right? There's 12V+ to the plug.
Is it possible for my car to even run without the noise? cause it does.
It doesn't look like the guts come out of the box with the four corner screws on the circuit board. I guess I'd be looking for an obvious bad connection.
Anyway does anyone think I should replace this now?

I read early S mans thread. (even tho I'm completely unqualified to do so)
I noticed that he shows the '76-7 box to be different from the rest. So if I replace the CD box with a bosch do I need to get only that exact version or will another 3 wire box do?

Are the MSD boxes easy to install?




poof pow bang.

bosch boxes whine, permatunes don't. which is yours? next check if the center wire in the plug has 12V with the key on.

MSD's are cheap, but don't last as long as the Bosch boxes, and often aren't repairable at all when they fail.

Some Permatunes are reviled, although there's a couple of models of these, and one is more reliable than the other. Apparently.

My '77 has a 6 pin Bosch. It makes a noise like an old-school flashgun charging with the ignition switched to "Run". Never heard of one not making the noise, but hey, if the car runs...

It's quite high-pitched - this is apparently the range of hearing that's the first to go if you used to put your head in the PA bins at rock concerts back in the day... Have you asked anyone else if they can hear it? :)

I'd be inclined to check the timing and/or fuelling before replacing the CDI, but, hey, if you got a spare, why not elminate a variable?

Sorry it's a bosch
yes, it has a full 12v with the key on. No noise
BTW John, I meant to get you the picture of my points distributor but I keep getting side tracked.

No spare CD/MSD. Plenty of other spare ignition parts!!:)

So are the guts supposed to come out? (?no user servicable parts?)
Is there a capacitor in there like a guitar amp that is going to kill me?

If it's not been opened, you can get it rebuilt.

If you open it, it's no longer acceptable as a core for rebuilding - so if you can't fix it, you're in a pickle.

Me, I know which end of a soldering iron gets hot, and I'm quite comfortable with DC and logic circuits, but that funky analogue stuff gets way too complicated for me way too fast. Read the recent thread on this forum regarding the trigger points etc. for the 6 pin box, and, if you don't understand a word of it, I'd suggest either picking up a replacement CDI box (either Bosch or MSD) or getting yours rebuilt...

They're available quite often on the classifieds. Or buy an MSD new for about the same money. I've not looked inside one, but some people are really quite disparaging about the build quality/design...

Alternatively, the Aussies make a direct replacment for the 3 pin and 6 pin Bosch units, as well as some interesting multi-channel stuff:

http://www.mwignitions.com/

They look to have about 5 dealers in the US, 2 of them on the West Coast.

If the misfire goes away when you "put your foot into it", then I would think that this indicates that your CDI is working, after all, no sparky, no goey.

So, ok, what does it take for an engine to go? Spark, fuel, air and compression.

Since the car does go at higher rpms (when you open the throttle plate), I think this would indicate that you have adequate spark, air and compression.

As your air flow increases, the valve metering fuel also opens. I think you have a fuel system problem of some sort. What are your fuel system pressures hot and cold? It could be that you have a fuel flow issues.

Hangin' my head in shame. I had promised I would only do stuff one thing at a time and well,,,,I got pissed and did 5 things (mostly re=establish grounds) and I don't know which one it was but I stopped the misfire/backfire.
At least I know which things they were tho.
So if it does it again I'll have it narrowed down. maybe........
So hangin' my head but my mouth is in the vicinity of a nice glass of chardonnay.

You know I think it was the points. I think they were too far closed. I (pre=chardonnay) eyeballed them and it looked like about half a gap so I stuck a piece of cardboard between them and well,,,it made the idle go up but no more backfiring/misfiring. I had trusted the mechanic from a few weeks ago to have had it right so I didn't dare mess with that since I'm so crappy with points. AND Paranoid now that I'm told my '79 engine in my '76S shouldn't have points and the distributor is turning the wrong way and the centrifugal weights won't fly and that it's all impossible. And nobody can tell me if I can use these pertronix E-ign's.

I drove it for about 30 miles and while I'm sure I don't have it just exactly right I bet I can get to work and back now. I filled it with gas to see how far off I really am. I used to get about 22mpg.

You know this place is pretty cool albeit overwhelming. There is so much knowledge and experience that is "complimentary" and "contradictory" that it makes a stooge like me just want to "go porschpostal". Gawd all those acronyms and electrical diagrams and part numbers and model numbers. It's too much for the common guy wanting to mess around a bit. Oh well....It is what it is.
Thanks to everybody.
Ho Ho Ho!!!!

PS..Now that I know my car has been in places that normal cars shouldn't go (ie. the parts being stirred around and all),,,,I'm going to name her "The Slut"
Yeah, The Slut...

Yes for sure I'll have to visit the fuel pressure flow issues too.
It still has the bouncy lurching accelerator pedal when I try to moderately accelerate.
But like I said. apparently these things will run under pretty rough circumstances like wrong way distributors.
Working on a direction.
Thanks

Send it to Ingo...he can test it and then let you know your options....email me for his contact information.

Errr. Wow.

You probably want to gap the points accurately. You definately want to check the timing after they've been gapped.

If your mechanic didn't do this "a few weeks ago", I think you need to either find another one or get used to doing it yourself.

For a '79 motor, that should be an SC distributor. Which turns the correct way, and doesn't have points, because it has an ignitor. 930 distributors turn "the wrong way" too. But the drive gear might be different, because they use the same crank/intermediate as the 3.2.

Mechanical advance working correctly on the distributor would probably make it run a lot better. I would think the bob-weights would still fly out, but the springs are unequal - so if they weren't swapped around, they'd be slower to close and faster to open than normal.

You should either hang out on the classifieds for a bit, post a WTB (wanted to buy) ad or, as you're in Oregon, see if Steve Weiner can help you out.

I'm sure you'd like having your ignition set up so you could use a regular book to set/check it..

new points should be re-gapped after a few hunderd miles. A good dose of Bosch points grease may see break in as long as 1.000 miles.

adjust points and adjust timing. Then recheck in 1,000 miles.

Since you opened up the point gap and it no longer has a random back fire/misfire, it is now time to check the ignition timing.
With the vacuum hose dis-connected and plugged, set the timing to Z1, 0 degrees, TDC at idle.

Will do!

Thank You Guys! Thank you very very much!

Not just "yes," but "Heck yes". You should go and give him some money immediately :D

Seriously, you're right next to an extremely knowledgable and helpful expert - who's pretty active on this forum too. Amongst his other talents, he also builds/modifies distributors.

Steve Weiner
Rennsport Systems
Portland Oregon
503.244.0990
http://www.rennsportsystems.com

If I lived in Oregon, I'd take my car to him like a shot.