Cold start problems? What cold start problems?

I looked and looked in my engine bay and can't find any WUR, thermo-time valve, enrichement screws ;)

CIS Hater :D

This thread needs a way to have it automatically reappear each season. :D

This is funny. I just went out and turned the 3mm screw a click back form the cold weather setting. I must be getting to know this CIS system now.

Are the PMO's any less sensitive to changes in atmospheric conditions? I've been considering switching to these for some time now. CIS works fine, now, until it's warm and sits for ten minutes, then on restart it won't idle right for a while unless I run it holding the accelerator for 2 minutes or so. EFI vs. CIS vs. PMO? ;)

We can't let the thred slip down the page!
I'm trouble shooting my CIS and this is valueable info.
I'm gonna print this thred so keep it coming.

I wish there was a pelican in RI that could take a look at it before I destroy my air box. If I have'nt already:rolleyes:

My car runs great after warm up. But cold starts require some skill. It starts right away then stumbles and dies. I have to do this about four times before it finally catches. I have to do it just right to avoid backfiring.

I think I'm too lean because my exhaust is very clean. Can't even smell exaust fumes very much. but it don't know for sure.

I'm gonna poke around with my acetyline for vacume leaks.
I just had the engine rebuilt and all the intake boots look good. I did have a sizeable backfire so I'm gonna check around the box also.
Pop off valve works fine but I don't know if it could take the backfire I had. Then again it happened in the garage so it was pretty load.

I guess the first thing I'll try is to richen the mixture a bit before I start it up cold and see if there is any improvement.
Any other ideas?

Brian, your cold start/running needs adjustment. PMO's are going to be expensive and you'll still have to deal with the cold starting on spring or fall mornings...unless the PMO's have a choke now.

Think of the CIS as a sophisticated carb...and your cold running conditions are a poorly adjusted choke circuit. There is not one thing that can be pointed at as the problem. Sounds like you just need a good tune up and analysis.

Ron...you need a good tune up and analysis too. Sounds like you have more air than you need on startup...could be lean setting or could be a leak of the AAV or AAR...or some other. Have you checked your fuel pressures?

We checked the fuel presures when the engine was put in.
I think they were 50psi cold and when warm around 30 psi.

We also tried another fuel pump for another un-related problem.

It should be the other way around. lower pressure cold, higher warm. What were your system and residual pressures?

From your description, try richening the mixture a bit and you might start easier.

Will do and thanks. I'm gonna get a gauge and go all through it. I'll let you know what I have for presures for sure.

It could be the other way around cause I was just enjoying the sound of my newly rebuilt engine being brought back to life . I brought the engine to a great wrench in boxes:D

souk funny you should mention this I just ordered a cis pressure tester and borrowed the 4 gas anaylizer from work . My car starts fine any time just when it warms up it runs a tad lean. I will get it up and running properly shortly.. Hey did you say you rebuild these WUR?? You have me interested

Bump. A couple of days early.

mwah , i have my gear (on the 924)wired up to a button on my dash
full control, and no hot start issues either, and no worries bout worn out thermotime switches or what not

and most of the time , i don't even touch that button , it just starts without

Souk - funny you should bring this up, my newly rebuilt engine in my 79SC 3.0L never has a problem starting with just a bump of the starter when warm/hot outside , or when the engine itself is warm/hot regardless of temp.

But our temps have just started to drop they are in the 40's at night now here in South GA and sure enough I am having a real problem with cold starts,

The engine trys to start but dies right away, I go through this for no kidding about 20 tries before it catches and then stumbles until it warms up, my exhaust smells like it it plenty rich.

I am leaning toward a bad WUR, it is the factory original one and looks it from the outside, I belive the cold start valve is working.

I found a company that sells rebuilt ones for $235 an I am thinking about getting one put on.

Todd

K9, sounds like a cold control pressure problem. Instead of spending $235 for a rebuilt WUR (which is a gamble), spend $75 on a pressure gauge and check it out. For an afternoon's labor, you can make your WUR adjustable, then you can set it exactly as it should be.

ianc

Gawd no don't think of the CIS as a sophisticated carb.

I'll admit it is better for cold starts (unless it blows up - but hey what's a big hole in a thousand dollar bill, anyway). But why buy a sports car that has the engine responsiveness of a tractor?

Of course, I'm a confirmed CIS-hater....

Randy Randy Randy,

In every way except instantaneous throttle response and ultimate high-RPM horsepower (NOT torque), the CIS is far and away superior to any carbs made. The world has moved on from 1965 for a reason,

ianc

I agree. But the world also moved on from 1975... so just jump to EFI...

Todd,

I wouldn't be so quick to swap out the WUR. Like Ianc said, get a pressure tester before you spend any more money. Does the car smell rich all the time? Or just during start up? You can be overly rich too. Sure the air is cooler, and one may think it should lean out. However, there are other things affected by the temps. The AAR and WUR are now slower to go to normal operations.

I would get the car running, then after it warms up (go drive it around) and check the idle mixture. Look for my thread on the "field adjustment" for the idle mixture.

Randy, throttle response difference is over rated. And the difference is hardly justification to swap out a perfectly good induction system. I've driven carburated cars, EFI cars, MFI cars and CIS cars. There is little I'm missing with my CIS car. Throttle response counts for naught when you mash the throttle at 3000 RPM or less. Anything I'm missing with my CIS car, I make up in shifting and drivng behavior. Put it in the power band and go!!!!!!! :D

Edit: Todd this thread is just over a year old :D :D :D

Souk -

Can you recommend a pressure tester set up and where to get it from ?

Thanks,

Todd SmileWavy

Thank you for all the info, Gentlemen. Think I'll buy the pressure gauge and books on Bosch fuel injection. Which one is the best? Edit: [Maybe covers my 944, too?]

Wayne sells a tester:

http://www.pelicanparts.com/cgi-bin/ksearch/PEL_search.cgi?command=show_part_page&please_wait= N&make=POR&model=911L&section=TOLtol&page=5&bookma rk=26&part_number=PEL-PP910450

As for a manual that covers CIS and DME...not on book is good enough for either in my opinion. I have a number of manuals that when put together would be adequate. As a start, I would recommend the Bentley manual. It's not perfect but it is good for CIS and other aspects of your 911 maintenance. Jim Williams his a great CIS primer...someone will come allong and post a link if I don't find it first...or you can search for his posts, and follow his link.


There are also other online sites good for learning CIS, some even have good downloadable PDF's.


One of these days, I'll write a book on CIS that pulls together all the available information....but that day will probably come when I retire...then there'll only be just a handfull of CIS 911's still running :( :D

Haha, don't be so sure, Souk.

I've been adjusting CIS cars since 1977. Look how many are still around today. With the care people on this BB lavish on these cars I wouldn't be surprised to see quite a few still around for quite a few years, as long as we can still get gas for them!

With a trusty 3mm allen, an occasional check for vacuum leaks, and a pressure gauge (optional-I just got my first one this year), along w/ the valuable info on this board, these cars should run for a good long time.

Just remember: spring/lean, fall/rich for those of us in northern climes. Usually no more than 1/8 turn is all it takes.

Maybe so Paul....rather I hope so :) Not that I think CIS is the only induction system out there, nor the best, but I like simple things that work well...simple for you and me :)

OK! Here is a collection of information that should be helpful:

CIS Diagram:

http://www.pelicanparts.com/911/911_...8-83/1-7-2.JPG

Mixture Adjustment w/o an analyzer:

http://forums.pelicanparts.com/showthread.php?threadid=232089&highlight=cis

Jim Williams' CIS Primer:

http://members.rennlist.com/jimwms/CIS/CIShome.html

CIS cut-away:

http://forums.pelicanparts.com/uploa...1130510551.jpg

Where did the CIS cutaway come from? I would like to get a copy large enough to read the print.

This Temperate Climate CIS thread should live on forever.

I know I'll read and probably post again in spring -- right here!

I've been thinking about doing just that!

Although I agree with Souk; the CIS is not the best induction system out there by far, but I like simple dependable things that work.

And Souk, that is a cool cutaway! Another vote for a larger version if you have one?

ianc

I did not create that picture, and I can't vouch for the text on it...(Edit: I should also add that the cut-away is not that of a Porsche 911 system, but it's close.)

It was posted in this thread (I don't know if Dr. Injection even posts here anymore. He never got back to me on the manual request :( )

http://forums.pelicanparts.com/showthread.php?threadid=164209

http://home.broadpark.no/~alejoha/kjetronic22.jpg

How timely is this post. I got in my car this morning, temp 30 deg F
Turned it over . Bang! tried it again. It would start and die, start and die. I pulled the air cleaner off and pushed the control arm up. I do this when it runs rough. The pop-off valve was completely blown off. I started it and the tach pegged. Not good. Took the other car to work. I believe this is all cold weather related. What caused the engine to rev so high? Is there somethind else that would cause this? It's going to be 65 tomorrow. The SC loves that temp.

You're bypassing the throttle (pop-off valve blow off right?), and there is enough fuel fed to the engine via the cold start sequence and your priming of the engine...so you essentially had an un-governed engine at that point....

...clean and prep as appropriate and reinstall the pop-off valve, richen the idle mixture a bit (1/8th turn to start with...). If that doesn't work...check for cracks in the airbox (cross your fingers). Good luck.

Souk,
Did I "break" something? Where would the cracks be?

Yep..you busted something.

Busted something as in pistons or valves?

bump

Don't worry Limble, you didn't damage anything majorly expensive. You will need to reinstall your popoff valve though,

ianc

I've got a question:

In the CIS diagram above there is a hose labeled 16 that attaches to part 54. On my '80 SC hose 16 is missing and the nipple on part 54 is exposed to free air. What does hose 16 and part 54 do?

From the looks of the diagram something on my CIS system is missing and possibly causing a vaccum leak.

-Scott

Hmm....I think I answered my own question. According to the CIS primer that nipple is exposed to atmosphere on '78-'79 and '81-'83 models. Somewhat strange though since my car is an '80.

http://members.rennlist.com/jimwms/CIS/WUR_photo.html

Hi Kaefer,

17a (which hose 16 connects to) looks like an altitude compensating device to me. I would try to locate 17a and see if the hose is plugged or not. It may also be that the WUR (#54) has been replaced on your car and the original did not have it.

ianc

That's one of the things that make Porsches like a rubic's cube: they made small changes just about every year to the CIS.
The hose you are talking about it a vaccum line to the warm up regulator #54 (control pressure regulator is the correct name).
On a 1980 US SC you don't have one, I don't either.
On some earlier years they had one, and on some later years they had one, but on a 1980 they didn't.
Thje decel valve (#7) is different also.

I saw this a while back and was saving it for a thread like this:

The world is divided into three types of CIS Owners, which one is you?

1) The guys with working CIS systems out driving their cars so they won't reply.
2) The guys that tinker with their CIS systems and have them royally screwed up and keep you running in circles with suggestions.
3) The guys that have spent a fortune on Webers, PMOs, EFI etc will tell you they're great to justify their expenditure to themselves.

Your choice. ;)