Interesting, I noticed that cold starting is more difficult now. Then I traced the circuit and discovered the enrichment solenoid is powered off of fuse 2 also. That tells me that the blown fuse is a recent occurance - after I soldered in the jumper. Now I am wondering if that little missing copper trace on the circuit board was actually "blown"?

Michael

So it is the RPM Transducer that is blowing the fuse. After removal, the enrichment solenoid works fine. I removed the jumper and tested with the RPM Transducer installed (knowing that it would not work of course) and the fuse did not blow. So, this tells me that there is a short on the board - likely at a component since the rest of the copper looks sound. I double checked under magnification all of the leads on the components and they are all remarkable clean and solid.

In looking at what components are soldered to the suspect copper trace, D1's E is soldered to it. So given that D1 is between ground and +14V, if it fries, could it not be the suspect short I am chasing?

I also discovered that the solder joints on the ground terminal (#3) were cracked. Not sure if they were like this or if I did this in my testing.

If D1 is replaced with a Zener (8.2v 1N756A) as per previous posts, how does one determine the values of R5 & R6?

regards,
Michael

Ok, I made it to the electronics shop and got the 8.2v Zener and transistor for T4. Got these soldered in, replaced the jumper and the fuse is still blowing.

At this point, I have gone way past the time-satisfaction curve of doing it myself. I am going to locate a used or rebuilt unit and go that route. I know Otto is supposed to have them. Any other options? I wold like to keep the original case since the label is in great shape and the patina matches the other items in my engine compartment. I wonder if Otto does a case swap?

Cheers,
Michael

Well, I finally ended up sending the transducer to Otto's to have rebuilt. I overnighted it on Monday and he overnighted it back so I got it yesterday/Friday. Plugged it in, fired up the S and tested the circuit. It hunted! I think this is the first time in my ownership that this circuit has worked properly. It was a pleasure to drive without the pops and backfires!

Now on to the other items.

Also, unfortunatey, on the way home from picking up my dughter from camp, I lost all my oil - suddenly (see http://forums.pelicanparts.com/porsche-911-technical-forum/357088-dodged-bulllet-i-think.html). Still have not figured out what is wrong there.

Cheers,
Michael