cold start/run oddities??? normal?

spinner37 · 10-17-2009, 10:46 AM

so i have a 77 911 that i bought about 3 months ago. i had it running pretty good. when temps are warm, it will fire, maybe quit. then fire again and run fine. this is first start of the day. it will idle to about 1600, then drop to about 14 then to about 1200 in about 1 minute. after that it starts first time all day, with the same rpm drops. runs good, still needs some fine tuning, but i put 300 miles a week on it

so now it is cold, 35 degrees. it will either 1) start and die 3 or 4 times, then start and run, rpms like summer or 2) turn over a few times, nothing, turn and fire but not start 3 or 4 times, then finally fire and run like always, high rpms that gradually drop. it does this after sitting a couple hours also, not just in the morning... any tips on this? i did search, and it seems it may be my cold start valve? i know the fuel pressure is off, will that casue this in cold weather? the other question, after driving 25 miles(city/highway) it is still not up to temp, the oil is only luke warm, if that, is this normal? it has 10 40 oil in it, i was thinking of going to 5 30 since it doesn not warm up??? any tips would be great, the heater works awesome at least!

psalt · 10-17-2009, 11:32 AM

Hello ?

No, not normal. You need to read up on your version of CIS and do some basic troubleshooting. Most cold start/cold running problems are caused by too lean mixtures and/or not enough ignition advance. If the engine fires, the CSV is usually not the issue. It is powered by the starter only in the crank position and is irrelevent after the key goes back to the ON position. The cold running mixture is controlled by the WUR, lower control pressure means higher air sensor plate deflection and more fuel delivery. You need to check hot and cold control pressure and system pressure before you can diagnose what is happening. Even if all the components are working and up to spec, you can still have cold start/running problems because CIS cannot compenstate for engine wear, lower compression and vacuum leaks. Then it takes some experience to find the best combination of settings for your engine and conditions.

Tips? Never use 10-40 or 5-30 in a 911 engine.

spinner37 · 10-17-2009, 12:23 PM

what oil do you recomend for cold weather, like i noted, the oil is getting only luke warm, so i thought lighter weight would be beneficial? thanks for the tip, i thought it might be the pressure, so that is what i will look at. maybe i can advance the timing slightly to help......is it normal for the motor to stay cool, that is what the"normal" part of the question was

HarryD · 10-17-2009, 01:26 PM

Can't help on the running issues but I would use a good quality 15W-40 oil. Many of the Diesel oils (Rotella, Delo, Delvac) are good selections. SWEPCO 15W-40 also comes highly recommened. If you have some time, check out Ultimate Motor Oil Thread or Why we hate CJ4/SM oils for some history.

spinner37 · 10-17-2009, 01:40 PM

i did read that thread before. i used castrol gtx whcih was recomended on that thread i think. hum, i still think 10 40 would be easier on engine wear and components if the car is running cold.....15 seems awefull thick for cold weather start ups..... anyways, any body help on the cold running, is that normal??? thanks again for any comments!

HarryD · 10-17-2009, 02:39 PM

Check for vacuum leaks.

Do you have a flapper valve in the air box? In my car, the glue started to fail and I had a small vacuum leak. When I fixed that, the problem of hard startign and erratic idle went away.

Several years prior, I had trouble starting the car. One day, I was looking behind the engine, and noticed that the electrical connection for the CSV had fallen off. When I reattached it, my car was much easier to start.

spinner37 · 10-17-2009, 02:50 PM

ok, i have a flapper i can check that, i will also poke around for anything loose. i think it has more to do with the cold weather though, it was fine when it was above 50 or so outside.... it has backfired a few times though, maybe something happened to the flapper....

Paulporsche · 10-18-2009, 05:10 AM

Spinner,

You have some more searching ahead of you.

It seems the most typical start/warmup/run problems w/ these cars comes from an out of spec warmup regulator (WUR). Search that and you will find volumes. A fuel pressure gauge is needed to check your control pressures, especially cold, which is important for starting and warmup. Your mixture setting is also important.

Check out Jim Williams. He has an excellent site on CIS.

Also check for vac leaks, as was mentioned.

But first, always make sure all ignition components are operating @ spec.

spinner37 · 10-18-2009, 05:34 AM

ignition is all new, can't find anymore vac leaks, might still be a small one. i need to buy the pressure gauges and check the fuel pressure, i have a feeling that is it. is it isupposed to run luke warm in cold weather?