CIS cold start problem
 

My 73.5 911 is extremely hard to start when cold. It had a hot start problem which I corrected by replacing the accumulator. In the last couple of weeks the cold start has become worse. It will initially start and die immediately. Then I have to crank and crank for 15 seconds to get it going. I have tried priming the system by leaving the key on for 10 seconds prior to starting but no luck. I dont want to start just replacing parts. I have thought maybe a check valve on the fuel pump, Cold start valve, and ???

Maybe warm-up regulator? Have you tested the fuel pressure?

http://forums.pelicanparts.com/porsche-911-technical-forum/52047-cis-cold-starting-problem.html?highlight=73.5

Is your hand throttle working? There is a plastic arm (in the center tunnel) that links it to the main throttle linkage. This arm can break. Also check the microswitch that powers the cold start valve. Also check your air box; is it cracked? Do you have a pop off valve? Jim

The Hand Throttle works fine. The micro switch is located where and how do I check it?

OOPs and yes I have a pop-it valve

"The Hand Throttle works fine." Does the gas pedal move when you pull the hand throttle?

"The micro switch is located where and how do I check it?"

It is located on the left side (driver's side) of throttle body just above the throttle linkage bellcrank on the left top of the engine. When you pull back on the hand throttle this switch should close and complete the circuit to energize the cold start valve. There will current supplied to this switch (and hence to the cold start valve) only while the starter is cranking.

Cheers, Jim

I have an SOS out on the board on a fuel pump check valve replacement for my 1973.5T/CIS. I had trouble early on with cold starting. If the hand throttle does not help, then you may have a number of problems. I went ahead and replaced my cold start valve and fuel accumulator for starters. I also replaced my warm up regulator as well which was pretty much the problem.

If your not very mechanically inclined like me, it may well be worth your while to have the fuel pressures and mixture (CO) checked at a shop to pinpoint the problem. With these older cars it can be anything out of wack (sensor plate, fuel distributor, injectors, WUR, cold start valve, fuel accumulator, old fuel filter, failing fuel pump, mixture setting, etc, etc). I have been exactly where you are now and fiddled with everything until I just took it to a shop and presto, warm up regulator!

You can go to the CIS troubleshooting chart in tech. articles for some extra help. Whatever transpires for the proper fix, replace the fuel filter more frequently (unless you have a new tank), check the points setting every oil change and from my own experience I add 10 ounces of Marvel Mystery Oil to the gas every three tank fill-ups. That tip came from a very reputable mechanic who cut his teeth working on these cars when they were new.

Best of luck
Bob