David0514

Hi, I was wondering how difficult a partial engine drop would be on a 77 911? Also would I need any special tools. I am considering replacing the cold start valve. Has anyone been able to do this without lowering the engine or would it just be easier to lower. Also, could I be opening a can of worms by doing this? Everything is great right now except the car starts poorly. The first two attempts the car starts and immediately dies, the thir or fourth it keeps running but barely. While it is sputtering it will backfiring. After about thirty seconds or so, the car will even idle better but you can still tell by listening that the idle is reving up and down very slightly. After about two minutes or so, the car will idle great at 9000 and continues to idle great until the car is started from cold again. Warm starts not a problem. What I have done includes tinkering with the WUR (adjusting) which help a bit, Mixture control unit adjusting screw, new air, oil and gas filters, new plugs. Anyone else experience this problem. The car is a 3.0 Euro not that it probably matters. Any help really appreciated. Also the car runs excellent when run for over a few minutes. Thanks in advance.

Chris Martin

I have a similar problem with my car starting hard when cold so I am interested in your post. I'm sure you have read the trouble shooting procedure for the cold start valve, the temp sensor must be working and wired correctly first.

This site and Pelican both have partial engine drop info, here's the one from Pelican <a href="http://www.pelicanparts.com/techarticles/911_partial_engine_drop/911_partial_engine_drop.htm" target="_blank">http://www.pelicanparts.com/techarticles/911_partial_engine_drop/911_partial_engine_drop.htm</a>

Please keep us posted on this!

Tom F

It sounds to me like your warm up regulator, not the cold start valve. You can get at the cold start valve without dropping the engine if you remove the heater blower and hoses, and snake your arms around the airbox. Symptoms of a bad could start valve, or bad thermo time switch, are hard starting (slow to catch), and near impossible to start in really cold weather. But, once you get it going, it should run okay even with a bad cold start valve. Bad warm up regulator will start up fast, but die immediately, or run rough until warmed up. At least that's been my experience with failures (at different times) of the thermotime switch and the warm up regulator.

FWIW, I've never had a cold start valve fail in hundreds of thousands of miles of driving Bosch injected cars, but it must happen sometimes.

1980SC

Dave -

Don't drop the engine just yet. Since you say the engine fires immediately, I doubt your cold start valve is the problem. The reason your car does start right up is because that valve is dumping in fuel. The warm up mixture is too lean for the engine to continue running.

Have you tried to lower the WUR's pin until it surges from being too rich?

Do you have a thermovalve? The K-basic CIS uses a thermovalve to keep vacuum away from the WUR while the engine is cold. If the thermovalve is missing, or stuck open, then your WUR will see vacuum at idle, and lean the mixture out. That's fine when the engine is warm, but not during the warmup phase.

You could have a vacuum leak somewhere. That can cause leanness during warmup, but not be noticeable once the engine is hot.

Check these things out and seriously consider a CIS fuel pressure tester.

Rob
1980SC euro

Bill Gregory

There's a write up on tech.rennlist.com on how to do a partial engine drop, by Walt Fricke. I've used the process many times, it's real easy in fact. Maybe a little scary at first, but follow the directions, and you'll see how easy it is - No special tools needed. I even used that to replace a blown airbox. So you can do alot on the CIS engines without dropping the engine.

Kevin G

If I had to explain the problem my 79sc was having your words did it perfect. Went through the process of tracking everything that could be the problem. Should have started with testing for air leaks first, the problem was bad manifold boots. The manifold boots crack with age and suck air, when the car was warm the problem went away. Good luck.

Kevin 79sc

Jeff Curtis

Kevin had a great suggestion...a cracked airbox could be the culprit as well - I had one, drove me nuts until I took everything off and found that the airbox had cracked along a seam.

Got a replacement and my SC ran great after that!

Just a suggestion of something else to look for...the other suggestions of CIS troubles were perfect too.

Good luck in finding the problem...let us know what you come up with.

David0514

Thanks for all your advice. Kevin, or anyone else that can help. When you say manifild boot, is that the seal between thge throttle body and where it attaches to whatever it attaches too. And to check for leaks, when i get the car to run on it's own no matter how rough it is idling at first, is that when I should spray carb cleaner around the throttle body and see if the engine performance changes. I have adjusted the WUR, I even took the step to put an adjusting screw on it. I am still yet to find a perfect balance between lean and rich. I may be backwards but lean would cause it to do what it is doing now (when the pin is higher in it's cylinder) and rich would cause it to start better but the engine would have a tough time finding idle (the rpm's bounce up and down until either it balances out or the engine dies. Adjusting the pin I have had both situations, but I can not remember if it started that much better when the WUR was richen. I will check tonight. For now if someone could let me know if I am checking the correct area for a manifold leak that would be most helpful. I will try spraying carb cleaner also. Oh, and if you could tell me when I should spray that would be helpful too. I apoligize for my novice questions, I never did any tinkering with cars until I bought this car a year and a half ago. Thanks in advance.

RANDY P

If you don't have a gas analyzer, spend a few dollars getting your CO checked and set before anything else gets changed. Mine was like that too when it was too lean.

rjp

David0514

I believe the WUR was the problem. I adjusted it a bit more and got to start a lot better than it was. No leaks anywhere, I sprayed carb cleaner all over the place when the engine was warm with no effects. That's a relief. Anyway, thanks for all your help.
David