CD Ignition Woes?

My '68 was the first year for the CD ignition, After 33 years has it expired? Here is the problem. The coil does not appear to be getting any spark. When touching bare metal there is a small spark when the ignition is turned off. Thats it. I am not hearing a whine at all. Any suggestions? If indeed it has died what should I replace it with? Thanks

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CM Wagner

1968 911 S Coupe
Light Ivory

Christian,

I just found 3 Perma-tune 3-wire units on eBay, 2 on a search for 'Permatune,' and a 3rd on a search for 'Perma-tune' ...

http://cgi.ebay.com/ebaymotors/aw-cgi/ebayISAPI.dll?ViewItem&item=556678269&r=0&t=0

http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=554910373

http://cgi.ebay.com/ebaymotors/aw-cgi/ebayISAPI.dll?ViewItem&item=555208921&r=0&t=0

You may want to try one of them.


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Warren Hall
1973 911S Targa

Hi there,
You're going to love this. I had a friend in town that had a porsche parts shop. I went in a few (six or seven) years ago saying that I think my cd box was out. He gave me a box of them and said that some might not work- so try all.
To make a long story short. It was my fuel lines that were clogged and burning out my fuel pump. So A few years ago, while I was moving, I found a box of cd units that I forgot to return. And the friendly guy was out of business. I don't feel bad- I gave him lots of body parts because I didn't have space to store them(on consignment). But I did try them all out and wrote bad on the ones that didn't work(he asked me to).
So, I've got a box of about eight. Put in your order if you want one, I will guarantee it will work...
Ed

WHat's the story with Permatunes?

A porsche CD unit costs almost a G-note. Why is permatune so much cheaper?

Will a CD unit going bad cause my car to miss at high rpms? My car runs fine below 5500 rpms, but abruptly cuts off above that. I've replaced plug wires, etc. and I am now suspicious of my CD box.

Thanks
Scott
1971 911e

Scott,

Is the miss present only under load, or can it be reproduced sitting in your driveway? If it can, I would suggest putting the engine on an ignition 'scope' or analyzer to see what happens with the waveform at high rpm vs at idle.


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Warren Hall
1973 911S Targa

Warren; As far as I can tell, it only happens under load. I can see what looks like fuel smoke out of the back when it happens.

As a possibly related symptom, my alternator light will glow very faintly, but not at idle. It would start glowing at about 1000 rpms. I took the alternator out and had it tested (ok), replaced my tranny ground strap, but not the alternator to engine strap (yet), had the battery tested (ok), and replaced the voltage regulator. The glow is now better and I can only see it when its dark outside.

I now feel kind of stuck. I have been gradually leaning out the MFI to see if maybe it helps. The plugs are very dark, but now wet. The car otherwise runs very well, but does take some cranking to start unless I activate the cold start spray into the intakes via my added switch.

Any ideas?

Scott,

I don't think the alternator 'faint' light is a problem ... most older cars do it, and I doubt if your CDI-unit is bad.

I would take the warm-up thermostat off the injection pump, disassemble and clean it, then reassemble and re-install. Then make sure the hose from the heat exchanger is not crushed or blocked. That thermostat needs to be cleaned anually, and it can get stuck because of 'inhaled' dirt, bugs, leaves, twigs, etc. If your plugs are black, they are fouled, and that alone can cause a high speed miss, so replace them ... I suggest NGK B-8ES, gapped at 0.028" - 0.032".

If you don't already have a copy of the 'Check, Measure, and Adjust' factory 'blue book' publication, it is available here on Pelican for download and printing:

http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

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Warren Hall
1973 911S Targa

I tried cleaning the warm up thermostat and installed a new "intra engine compartment" hose (actually a hose within a hose). How much air should flow through it? I can feel some air flowing, but it isn't much. I wonder if my hose underneath the car is plugged or if only a little air should flow through it.

I will replace the plugs with your suggestion. Can an over-rich condition cause a high speed miss such as this? Or do I need to look for other causes like a coil, etc.?

I'll go through the Check, Measure, Adjust manual. Thanks for the suggestions.

Scott

Hey Warren, How hard is to clean that thermastat. Is there any Danger of messing it up!!..ie are there any surprizes other than disks to clean, and keeping them in order..

Scott,

I guess the big question is whether the air you felt was hot after the engine has warmed up for ten minutes? If not, maybe the heavy rubber hose to the heat exchanger needs to be run through with a broom handle, and cleaned out with soapy water and a bottle brush.

And, yes, an over-rich mixture can cause a miss at moderate to high speed after the plugs are fouled.

72S,

The regulator is very easy to disassemble, easier than a one-barrel Solex carb! Assuming you don't leave out the spring, or put it on the wrong end of the housing, there is little chance of messing up. Wal-Mart sells enough Berryman B-12 Chemtool for $2.37 in a 16 oz can to do the clean-up twice!

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Warren Hall
1973 911S Targa

Thanks Warren, I give it a try..Wayne

The saga continues, early_s_man.

I have put in the ngk plugs you recommended, gapped as recommended. I also double checked my plug wires. My plug wires each have 1k ohms of resistance. They do not have the resistor end connectors on them. I saved all the resistor connectors from the old sets.

I still have the miss and my car turns over many times before starting (unless I force the fuel solenoid to inject fuel into the stacks, at which point it starts immediately). The car seems to run fine, until the miss kicks in.

Just to recap, I have replaced plugs, plug wires, voltage regulator, checked the alternator, leaned out and enrichened the MFI, replaced the tranny ground strap, and cleaned connections all over the engine compartment, all to no avail.

Should I be suspicious of my CD box? The miss occurrs at 5200 rpms and acts like a rev limitor has kicked in. Any insights on the miss? What happens when a CD box fails?
Could the lack of resistors on my spark plug wires cause problems with the CD box?

I'm starting to wear out on this one. Any advice is much, much appreciated.

Scott



[This message has been edited by wslynn67 (edited 03-15-2001).]

Scott,

It sounds like your wiring between the Thermo-Time Switch or the switch itself is bad or you would not have to crank so long!

I don't think the lack of resistors at the connectors is a factor.

Have you compared the air flow at the outlet of the heat exchanger for the warm-up thermostat on the injection pump with the minimal flow at the hose you noted before?

My suggestion at this point is to take the car to a shop and have an ignition scope check the output of the CDI-unit/system. The coil may be bad or failing, just as easily as the CDI-unit. It would be nice to know the amplitude of the pulses at the coil terminals ... 350-460 Volts is the normal range hot/cold.

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Warren Hall
1973 911S Targa

I forgot to add that I replaced the coil. I do get good air flow to the thermostat. This should just lean me out as the car warms up though, right? Wouldn't leaning out the MFI pump do the same thing, just not vary the mixture with engine temp?

What temperatures should cause my thermotime switch to turn on/off?

I'll try to get the CD output checked next. Thanks.

Scott

Scott,

I believe the ThermoTime switch opens somewhere between 107 and 112 degrees F.

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Warren Hall
1973 911S Targa