See Dr. Sturm reference at bottom of this page.

http://www.lunarpedia.org/index.php?title=Rocket_Pioneers,_Schemers_and_Drea mers!

Yes. The price of a brand new Perma-Tune unit as compared to a OE unit or used, of unknown quality OE unit. When an electronic component in a hot engine compartment lasts 10 years as my Perma-Tune has...I find it hard to complain about value (from what I have seen here on Pelican, unlike me, the majority do not keep the same 911 that long. If the choice is an OE unit that is already over 25 years old and costs twice as much...it seems the shiny new Perma-Tune is not a bad idea.

"If the choice is an OE unit that is already over 25 years old and costs twice as much
it seems the shiny new Perma-Tune is not a bad idea."

Not based on this forum for over ten years!
And the cost difference is NOT twice, and most likely the Bosch will be less.
Sounds like someone didn't do a thorough comparative price analysis.

Bottom line: Like suggested to others, buy a spare CDI - you're running on luck.

Back again.........drove the car home without a hitch, started to tidy things up after my troubleshooting session and guess what, the car fired up ran for a couple of minutes and then died.......no spark, very frustrating.

I slaved in another known good coil but to no effect, to say I am frustrated would be something of an understatement.

Sounds like an intermittent CDI unit.

I have been posting here for 10 years and an awful lot of bad info has been posted on this BBS from time to time....although usually it is corrected. I also recall that you (expert that you are), get a significant bit of argument from time to time (particularly regarding performance chips)...As I said, one of the best regarded, most experienced Porsche mechanics in the world put one in mine 10 years ago and it has performed very well. Seems that he thought it was a good idea...and the low cost and longevity proved him right. Any chance that your business rebuilding the Bosch units might influence your opinion a bit? Seems a bit inappropriate having you attack another's product here when you compete with him (but I know you have heard that before).

"Any chance that your business rebuilding the Bosch units might influence your opinion a bit?"

Not really. Most who know Porsche cars (pre 911 3.2s), e.g. independent Porsche
shops, that use CDI units have concluded the same over the years as have those
who also expressed their opinions in this thread. As was stated previously, the early
blue Perma-Tune which was used as an original equipment on 1976 911 was as
reliable as the Bosch.

It now appears that this thread starter may have an intermittent CDI.
One of the purposes of this forum is to provide members insights into potential
problem areas/parts that may be costly not only in the initial product purchase
but the additional costs related to a car breakdown, costly towing, or a lengthy
troubleshooting effort. Most members are capable enough to do searches beyond
this thread and verify whether statements made herein have any credibility or not.

Sorry to hear about your continuing problems....a quick shot of ether into the intake will tell if it's a fuel issue....cough...fuel problem, no cough...either fuel or spark.

No cough, I would suggest pulling a plug wire and checking for spark by attaching a new plug, ground ing it while someone cranks the motor....no spark?

I have not seen where you have paid assistance on this? If so....I would start on the aftermarket box....the guy from Permatune says he'll test it.

I would take them up on that and test BOTH the old coil and new.

CIS is pretty easy to cehck if you have the equipment. Shot in the dark....Is the fuel pressure to spec?

Just because you imply I am a bit slow or uninformed ...doesn't mean I will necessarily agree. As an engineer myself, I would have to expect that you must have some sort of failure statistics to base your claims on. Maybe you could share those. I'm sure the Perma-Tune dude would be interested as well. He was very polite while you trashed his product. It is exactly what we want on this BBS for manufacturers to come here and support their product and hear our concerns. If they do, they deserve fair treatment.

Obviously the factory units fail, because otherwise, you would be out of business. As a consumer, my Perma-Tune has never failed, yet you make fun of my assertation it was a good value??? It omly makes sense in one context...ulterior motive.

The fact that you have posted as a CDI expert and been running down Perma-Tunes and pushing your product here for the last ten years may just have just influenced the discussion a bit...repeat anything often enough, it becomes the accepted fact, but not necessarily true. Here is one from around 2003 vintage (there are many, many more):

http://forums.pelicanparts.com/porsche-911-technical-forum/122888-coils-coils-coils.html

Joe Bob is right...always suspect the most complicated and heat sensitive electronic part...that would be the Perma-Tune CDI unit...get it tested by the Perma-Tune guy if you don't have a part to swap in. Personally, I bet the problem is distributor-related.

I had the perma tune tested last week by Zims, it checked out good so unless it is intermitent......

I have confirmed that there is no spark out of the coil.

Can smell fuel after cranking.

Looks like I will be testing the "green wire" tonight.

"Looks like I will be testing the "green wire" tonight."

A simple test which will take less than a few minutes:

1. Use an ohmmeter to check for 600 ohms.
2. Have someone crank the engine and check
for about .200 VAC - .300 VAC (200mVAC - 300mVAC).

Also check with a test light for 12 volts input. Check that
there's a good connection from the CDI output to the coil.

Jim, I would be happy to walk you through troubleshooting real-time, if you would like, and will make myself avaiable to you tonight up to 10:00 PM Eastern time:

(631) 909-1011

Got in the car tonight and it started first turn of the key, in fact I have had it running all evening on and off with no problems so I'm afraid there was nothing to troubleshoot.

Dont know if I fully trust it so I will drive it around a bit tomorrow to see what happens.

200 yards from the house this morning and it stopped again...........

Do you have the ability to test for spark or fuel?

Yes,

I tested for spark the last time this happened and there was nothing.

Strong fuel smell after every crank. Lifted airflow plate and injectors scream with strong fuel smell. Confirmed fuel pump is running. I dont have CIS test gauges however.

It doesnt feel like a fuel issue.

Anybody near you that you can borrow a CDI box?

Like I said, I am here to help, all you have to do is spend $5 to send me the unit to test it. I even offered to help you trouble shoot the problem over the phone...

You can't ask for any better than that. Thanks for helping out here on Pelican.