78 911 sc FIX

[gshase]

THIS, A POST ANSWER TO MY BROKE SC. I HAD JUST REPLACED 6 INJECTORS AND SHE RAN FINE.....TWICE........NO START AT ALL.12V TO CD, .86VAC FROM IMPULSE GENERATOR ,AND ZERO V TO COIL .THE $ 100.00 BENTLEY MANUAL HAD SOME ANSWERS BUT , NO VOLTAGE CALL OUTS OR HOW TO TEST THE COIL. A SAD BOOK FOR THE MONEY. I LIVE IN THE D.F.W. AREA OF TEXAS AND I TOOK MY BOSCHE C.D. BOX TO ZIMS'S 1800 356 2964 WHERE THEY HAVE A GUY TO BENCH TEST IT . THE POWER CAP WAS BLOWN. $ 20.00 FOR A 100% ANSWER ON THE BENCH TEST. THANKS TO ALL FOR YOUR HELP.

[oneblueyedog]

i've had to buy 2 cd boxes (rebuilt) in the last 5 years. When this one goes (I suspect it already has) It's Permatune time. I'm sick of the Bosch units. The first one almost burnt up my cart limping 2 blocks from my house. The Cat melted and the rubber gasket caught on fire in the engine bay.

It was an intermittent problem when the car got hot. Only way we could diagnose it was to replace the cd box with a known good unit when it would start missing and bogging down. It was indeed the CD box. We replaced it and the transformer(coil). PIA!

Second time, after the car got hot the cd unit squeak would go off and on and the car would run like crap when the whine would go off. Easy diagnose. Expensive fix. I wish there were a publication on a dyi fix for these things. It couldn't be too hard to fix. It's 1970's technology. We can rebuild engines but not a cd box?

[Doug Zielke]

I'm sure Warren Hall could fix them, if he wanted to. He has posted the occasional details about the components. Maybe if you asked him...nicely.

If you think a Permatune will end your problems, you're in for a surprise.

[red-beard]

CD boxes can't be too difficult to build. In a box of engine parts I bought there was a Heath kit CDI complete with the build instructions.

James

[Wayne 962]

The Bosch units are very reliable. If you had two of them fail in a very short period of time, I would guess that there is something else in your electrical system causing them undo harm. If this third one fails, I would look at your wiring, instead of your luck...

-Wayne

[oneblueyedog]

Indeed I will since I have the engine apart. The wiring harness is suspect for all of the components. I unwrapped the complete harness and found insulation that was worn through in various places. Brittle wires were also numerous. They were only brittle where the wires came out of the sheathing. Needless to say I'm restoring the harness. Anyone have any suggestions on where to get sheathing and what tape to use?

I have to add that I have replaced the CD units with rebuilt ones. So I have to blame myself somewhat for buying cheap-going on buying three times.

My engine also ran hotter than most. It registered almost to the red on some of our 108 degree days around here. My friend's SC rarely goes over the middle of the temp range. Another reason I was curious about what was going on inside the engine. I found a bearing and journal damaged on one of the mains. The bearing and crank is at CE. I doubt it caused it as there was no heat damage. But metal had gone through the engine and it had been rebuilt on one side. It could have been timed incorrectly on that bank. Metal or dirt could have been introduced into the engine at that time. It could have clogged part of the oil cooler. I'm replacing it too. Heat destroys electrical components so maybe the rebuild will solve it eating CD units in various ways. All I know, I won't have to suspect the engine.

I'm not rebuilding if because of the CD unit though.

[Wayne 962]

Hmm, sounds like you have multiple problems. I would suspect the wiring for blowing up your CD boxes...

-Wayne

[Jared at Pelican Parts]

Spent all weekend working on something similar to this.

In the case of the SC cars, there is a green wire going from the impulse generator to the CD unit. I could not get spark to the ends of the wire leads. I went through everything on the system and eventually checked the resistance on the inner wire inside the sleeved green wire. Bingo... Replaced the wire and it fired right up.

[Wayne 962]

Electrical problems can be very frustrating, especially when they are intermittant...

-Wayne