Possible problem

[frankmar]

I finished full restoration of a 1969 911s. Everything was taken a part and put back toguether. The car is beautiful and really great to drive. But, I think the car has a bug somewhere. The car was a bit hard to warm up at the beginning compared to my 67. Then the car used to stall a couple of times in the first few miles until fully warm. It usually stalled going down hill lifting the accelerator at low speed. Then you could easily re start the car and keep going. But there was a time that the car stopped and I could not start it again. It burnt the coil and the CDI box. The coil was a silver one that looking at this site didn't seem too reliable. I changed the coil with a used black one and also de CDI box. After the change and using the startup procedure in the manual it worked really well and it did not stall anymore, the car idled higher when it was warm and it all seem fine. I've driven the car about 300 miles since then with no issues, but today the problem happened again it stalled in the first couple of miles going down hill. I started the car back with no issues. Is the problem back? :-)

Something that I find different compared to my 67 or 75 Carrera is that when lifting the throttle fully the tachometer needle goes to 0 and almost bounces of the lower point of the scale and then stabilizes.

[platas]

Frank, it sounds that theres something wrong with conections from the cdi, since you allready replaced it, maybe Ed could saher some light here.
I think you are going to have to take it to IBR, he is pretty good at locating these problems.

[edmayo]

Have you checked your ignition point gap?

[frankmar]

I checked the gap before when I had the first problem and it was fine. I was not able to reproduce the problem again. Maybe something to do with the fuel pump? Since it happens going down hill...

Also, I read that the 911s migth be a bit more prone to stall when cold than other Porsches.

[beh911]

Do you use the hand throttle during warm up?

If so,are you saying the car stalls even under the guidance of the hand throttle?

Trying to help you narrow down to an electrical or tune/adjustment issue.

[mikael]

Could the RPM relay be malfunctioning? It is supposed to cut fuel delivery when you're off the accelerator and RPMs are over a certain value (2300 I think), then open again when RPMs drop (to below 1300 iirc). Perhaps once triggered it doesn't open again?

[frankmar]

No the stall happens later without the use of the hand throttle. What Mikael says could be the problem... Do you have a picture of this part for a 1969s. Is that a silver cylinder?

[mikael]

The RPM transducer on my 72E was a square box, I assume that it would be the same on a 69.



Mine was not working properly so had been disconnected by adjusting the microswitch until it never engaged. I guess you could do that and see if the RPM transducer is the culprit. The transducer contains a couple of components with unprotected copper legs that tend to wither away, but are easy enough to replace. Here's a post describing what was done to mine: http://www.early911sregistry.org/for...438#post576438

[frankmar]

Hello Mikael,

Do you know where I could buy a new transducer box?

[frankmar]

I repro the problem again. Going down hill after warning up the car for about 5 minutes, probably still a little cold, second gear and about 2500 RPM without the accelerator or hand throttle engaged. I press the clutch and set the car in neutral and the car stalls. The RPMs go down quickly all the way down, it looks like the tach needle wants to bounce of the bottom :-). It seems almost like if you would turn the car off. Then you can start the car back without any problems.