911 w/ MSD ignition starting trouble

AlienTekniX · 02:55 AM

I have a Carrera RS clone that has 1970 911E 2.2 liter w/ CIS. It has the MSD 6A ignition system with the standard Bosch distributor. I overlooked the distributor as a problem because the MSD w/ the Bosch blue capacitor had what appeared to be a good spark, enough to even fire a couple of plugs to make me think the ignition system was fine. When in reality it was the rotor's resistor that had long since blown and the MSD + cap were able to arc across what was left of the resistor! My guess is the far greater voltage and the multispark system was enough to blow a quality bosch rotor in less then 6000 miles. So anyone with an MSD ignition system should quickly check the distributor condition as an intial diagnosis step.

Hopefully this helps someone. Thanks Rocc T. for spotting it.

Chuck Jones · 08-02-2006, 11:33 PM

THANKS: I recently installed the MSD 6A also...and didn't think to check the distributor..and when I did, I found that the rotor had "extruded" a ribbon of plastic from a longitudinal crack that opened dead center down the length of the plastic about 1/2 inch from the metal tip. Your helpful hint about checking the bosch rotor has merit. Chuck

RoninLB · 08-03-2006, 03:45 AM

good subject for a couple of newbies. I wonder if any MSD guys have ever had trouble with the stock Beru plug connectors. I only dumped rotor and Berus on instinct.

RoninLB · 08-03-2006, 04:07 AM

Quote:

Originally posted by AlienTekniX

My guess is the far greater voltage and the multispark system was enough to blow a quality bosch rotor in less then 6000 miles.

I don't have any hard info in my head but the delivered voltage is only what's demanded. This was a good subject awhile ago and maybe a pelicanhead will remember.. Then again I just saw Early_S_Man/Warren on another thread. If we're lucky he'll throw a comment.

welcome aboard... and set up signatures as an outline.

kach22i · kach22i's Garage

There are conditions/situation where your are supposed to use a rotor without a resistor and or fry the resistor on purpose and make it non-functional.

I 'm sorry I don't recall which cars require this, I kind of recall it messing up the tach reading or something for some.

AlienTekniX · 01:21 AM

The last post makes me wonder if the guys who Frankenstein'd my car together didn't actually try that. I have tach issues and am considering just getting a G-techpro SS soon and skipping any further mysterious tach problems.

My main issue is this though...
When testing for spark by grounding the white wire from MSD 6a box , I get a spark, BUT when I spin the starter no spark at all now. Before I had changed my rotor(with blown resistor) I got some intermittent starts but it just wouldn't stay running. Now I have a new rotor but I am not getting a spark when I spin the starter. Does anyone have a suggestion???
Is the blown rotor resistor indicative of an another issue in the distributor (blown condenser also now?)? or maybe on purpose as a tachometer hack and I need to look someplace else?

In case it helps, here was the blow by blow of the failure
1- night before ran perfect
2- jumped in warm afternoon, turned key started perfectly ran for 3-5 seconds then stalled
3- would not run again but intermittenent starts
4- pressed fuel plenum for injectors to spray fuel
(common need for my car during hot day/warm starts)
5-still intermitten starts
6- tried plenum again
7- turned key-extremely loud backfire or maybe resistor(or something else) blowing? (sounded like a shotgun)
(let sit for 30 mins for fuel to evap)
8-intermittent starts ( a little poorer)
9- found rotor w/ obvious damaged resistor ; changed rotor (checked MSD for spark- YES)
10- NO spark when turning starter; NO intermittent starts
11- ask for help

question sanity of purchase

AlienTekniX · 08-04-2006, 02:36 AM

Kach22i:

Does this paragraph ring any bells for any reason you might need to destroy the resistor:
from MSD .pdf:
FOREIGN VEHICLES
Due to the fuel injection systems, some foreign vehicles may require a special Tach/Fuel
Injection Adapter to use an MSD Ignition. See pages 7 for wiring and Tach Adapter
information.
Note: Vehicles originally equipped with a CD ignition control cannot use an MSD.

Andy Ring · 08-04-2006, 05:10 AM

I'm sure others here know way more than me, but I'll relate my MSD experience in case its a help:

I installed a MSD 6AL in my 69T. After a couple days, it stopped working. After fiddling around aimlessly for a couple days, I called MSD tech support and they told me that I no longer needed a condenser with the MSD and that the MSD would quickly fry one. I removed the condenser and she fired right up. I'd suggest calling their tech support line--they actually seemed to know quite a bit about Porsches.

RoninLB · 08-04-2006, 08:18 AM

I rewired the MSD install completely. Hot main feed from starter lug with 10ga wire. Used pn 8207 MSD coil mounted on elec console. Used Magnacore long coil to dizzy wire. I used MSD tach adaptor.. No condensor

The install is not completely according to the MSD instruction book.
This has been covered a few times here.

Otherwise remove dizzy trigger wire and check if points are operating and connected to dizzy ground.

kach22i · kach22i's Garage

Quote:

Originally posted by AlienTekniX
Kach22i:

Does this paragraph ring any bells for any reason you might need to destroy the resistor:

I'm going off what I read 1-1/2 years ago when I was still considering MSD. There was a great article I read which changed my mind about the whole concept, can't seem to find it now.

Listen to RoninLB, he got me through some of my ignition problems and knows his stuff. Nothing beats a fresh lay of your own wires.

RoninLB · 08:50 AM

MSD wiring advice (connectors)

http://www.pelicanparts.com/911/911...l_diagrams.htm.

http://forums.pelicanparts.com/porsche-911-technical-forum/152269-msd-yes-no-post1208543.html

http://forums.pelicanparts.com/porsche-911-technical-forum/213066-rotor-button-melting-why-2.html#post1832405
You want tall VW rotor, not the short one. JW says 72-77 VW rotor.

my non rev limit rotor written 04038/ 1 234 332 300 on box.
Pelican receipt pn Bos-04038

PERTRONIX PART NUMBERS---
Pertronix in a 1977 Euro Carrera 3.0
part#1867

also
MSD questions

Help with MSD install, please or Help For Dummies??

AlienTekniX · 08-04-2006, 05:46 PM

RoninLB: it was the points!
I just pulled an all nighter trying a few things when I decided to check the impedence of my points which turned out to be infinite!
I turned the ignition on and shorted the points, crackle! Coil fired!
Scraped points with needle nose pliers...
Put everything back together, vroom! First turn. Thanks everyone for kickin' me some info and listen to RoninLB he called it quick while I was sweatin' and experimenting.