Hard starts on 911sc

[jerkan]

Completed checkout of my CIS and all is well and in spec including cold and warm pressures. The warmup regulator appears to be working fine and the car starts well after a few seconds and the AAR is taking over to raise the idle as it should for several minutes. When warm, the car runs great. My question is that when I first start the car, aka cold start, it hesitates for a few seconds and the idle drops way low,, almost dies, catches and then goes fine into the warmup cycle. It sounds like the cold start valve is not working. Any ideas out there on how to troublshoot this?

[vash]

naw, once the car starts the cold start valve is outta the picture. my car does the same thing, but i have the hand throttle to mask the stall. i totally suspect my mixture is rich. but it does run so damn good when hot. i think it is the payoff.

[konish]

jerkan,
Souonds like a rich mixture to me as well...although I'm guessing here. I have an 83SC with K-Lamda (different systme than yours), but the freq valve wasn't working. Anyway, my car did the same thing and leaning it out helped out some....getting the freq valve made all the difference in the world. having said that, it can't hurt to lean your CIS out just a bit and see if it helps...

R/
Dustin

[Erakad]

Got to admit, mine's a hard start too. But add the drop in rpm,etc, plus some backfiring. But, once hot she's a champ! Am I in the same bag with a fuel mixture problem?

[Hladun]

The car will initially fire as a result of the cold start injector. When you stop cranking (or after a few seconds of cranking) the cold start injector is off, so it's not the problem any more when the engine fires.

The problem is that it takes the air flow plate and fuel distributor plunger some time to move and that's where you get the rpm drop and possible backfires (too lean). The added internal friction and cold oil when the engine is cold keeps your rpm down for a while.

I think this is just a characteristic of CIS that you can't do much about. In it's favor, I've started my 78SC in -30 temperatures.

[bigchillcar]

jerkan,
don't know the history of your car, but is this a new condition you're experiencing? in other words, has it been running fine until sometime recently? i agree with the others...the cold start valve only functions to enrichen the mixture during cranking. then, the warmup regulator gradually leans the mixture out as the engine warms (thus heating a bimetalic strip internal to the wur effecting the leaning).

my car is a '74 with a hand throttle to permit a higher idle adjustment during warmup, but i know yours doesn't. however, i'm wondering if you're idle is set correctly. at 180 degrees, does your idle hit ~ 1000 rpm's as it should? perhaps the idle air bypass should be adjusted...may be too low right now. on the other hand, i agree with the comments that cis isn't its happiest when cold, period. if you suspect mixture, take it to a tuning shop and check your co percentage and rule it out. it's a good idea to have it done regardless.
ryan

[jerkan]

I previously had a problem with hunting during warmup and the high idle not kicking in. I got the fuel injection tester and set all my pressures and came to the conclusion that my accumulator was leaking and the cold control pressure was off. I made my WUR adjustable, set all the pressures for a 79 911sc and put in a new accumulator and it solved all the problems except for the initial start. Can't remember if it used to do that or not before the tuneup..I think it did. It used to backfire also and I had to start it several times. Now it does not backfire and does not require a restart, so the situation is definitely improving. the only thing that I have not tried is setting the CO to 2-3%. I have been adjusting it by the sound of the engine.

[jknapp]

Hi jerkan

I have an 81 911sc that recently started exhibiting the exact same symptoms. When I was researching I came across your thread. Did you ever get this resolved?

Thanks

Jeff