1977 Cold start and running problem

[glenncal1]

Hello-looking at a 1977 911 that has a very difficult time starting when cold and warming up. It runs and starts fine when the engine is warm. I am not real familiar with the CIS systems, any ideas?? TIA

[ruf-porsche]

cold start valve or thermo time switch. Maybe the warmup regulator. Need a little bit of more info such as how cold does the problem start, does it start ok on a warm day? Does it have the problem from sitting over night?

[glenncal1]

Thanks for the reply-will get some more details and post them.

[David]

I'd start by searching the forum. In leu of that I'd go buy a CIS pressure test gauge. Sounds like your WUR.

[kach22i]

It's an old car.......needs something called "warm up peroid".

It might drive you crazy trying to fix it (could be so many things). Is it so bad that you can't just live with it the way it is?

[IROC]

I agree with David (125shifter). I bet it's the warm up regulator. The best way to attack this is to buy a cheapo CIS tester (pressure gauges/lines) and check your control/system pressures, etc. This is alot better than simply replacing parts until it runs better.

Mike

[pohsche]

Buy guages. I have put it off for so long and know that I have them, my car runs like it is supposed to.

Alan Poh
'77 Carrera 3.0

[Paulporsche]

Search for WUR to find out more. This is very common w/ CIS cars of this vintage.

You can get the CIS gauges @ JC Whitney. Your control pressure chart can be found in the CIS book that came w/ the car.

Typically w/ these cars the cold control pressure increases over time, which causes a too lean mixture @ startup. This pressure can be reduced by a process known as "knocking the plug". Some even make the WUR more easily adjustable but that is not really necessary.

Other things may be involved, like vacuum leaks, AAR or AAV, but the WUR seems to usually be the culprit. If the car starts, it is not the Cold Start Valve.