Andy Antipas

I have been try to chase down my cold start problem on my '79 911SC RoW coupe. I have James Weber's book on CIS, which is very helpful.

- CO, idle, timing at factory specs.
- Engine starts from hot pefectly.
- The warm up regulator works per spec.
- Once engine catches/starts from cold it fast idles smoothly.
- Once engine is warm it drops to 950 rpm and stays there.

I wanted to check the cold start valve, but based on Pete's advice, I decided to check the thermo time switch, which is easy to reach.

I checked the the resistance from cold and once the engine was at operating temperature and here are the results:

Thermo time switch is made by VDO and is stamped 45C/9.5s

resistance from cold:

terminal G to ground = 23.5 (30-40)
terminal W to ground = 0.5 (0)
terminal G to W = 23.5 (30-40)

resistance at operating temp

terminal G to ground = 59.2 (55-85)
terminal W to ground = 97.4 (120-160)
terminal G to W = 38.6 (55-85)

Values in (__) are from Weber's book. It looks to me that my switch is out of spec and needs to be replaced, but would like to hear from the experts?

Thanks for the help in advance!

Best,

Andy Antipas
(also F1 fan)

Andy Antipas

Bump.

If anyone could offer some feedback it would be much appreciated!

Thanks,

Andy

TroyN

bump for Andy, also interested...

Superdave1

I have the exact same problem. Working on the fix for months. Several mechanics have had a look. Let me know if you come across a solution.

dave...

theiceman

i woul dcheck for you now problem but my car is blowed up .
I can at least verify the cold conditions for you .

PS the cold start injector would also be a possibility no ? and it would be a nightmare to get to