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Car Forum / Porsche / Porshe 911 / May 2004Porsche 911SC 1978 not running when warm issue. Help.
I have a 78 911SC with 70000 original miles. It has never given me a days problem for years until yesterday. After driving 10 miles, I started her up to go home. She started, went into the cold-start cycle with a high idle, but when the cold-start cycle ended and she returned to normal idle she died. Would not start again. There is gas and abple battery power. Got towed home. :( I tried to start her at home and she starts running, and immediateley dies like there is no fuel. In the morning she started perfectly but died again after cold-start idle cycle. Any ideas? Must this not be the warm idle regulator? Warm control pressure? Cold start valve? Help? Martin Folb Martin - I think the best thing I can recommend is to check your fuel pressure. That should give you a real good idea of what's going on. Unlike the normal running injectors, the cold start valve is electronically actuated. It may just be that you have insufficient pressure to open the injectors to keep the engine running once the cold start valve closes. When it first starts, is it responsive to the throttle or does it just idle? regards,  SignatureMark Hald '77 Carrera 3.0 http://members.rennlist.com/hald > I have a 78 911SC with 70000 original miles. It has never given me a > days problem for years until yesterday. After driving 10 miles, I [quoted text clipped - 11 lines] > > Martin Folb > Martin - > [quoted text clipped - 7 lines] > > regards, Mark, when it starts, it runs for +- 2 minutes at 2000 rpm and then drops down to 900 at which point it starts coughing and then dies as if its running out of gas. During the 2 minutes I can rev the engine as normal it seems. It appears to be just fine. > > I have a 78 911SC with 70000 original miles. It has never given me a > > days problem for years until yesterday. After driving 10 miles, I [quoted text clipped - 11 lines] > > > > Martin Folb Martin - A device which comes into play during warm-up is the Warm Up Regulator [WUR]. It applies a control pressure to the system pressure regulator in the fuel distributor. When cold, the WUR supplies a lower control pressure, thereby allowing the fuel distributor to flow more fuel to the injectors, richening the mixture. When the WUR warms up, it raises the control pressure seen by the system pressure regulator, leaning the mixture. I suppose, if the WUR's control pressure were too high, or if the system pressure regulator were faulty, it could be leaned to the point of fuel starvation. I would definitely suggest checking your fuel pressures. There are a number of tests you can do to isolate problems such as this. mark > > Martin - > > [quoted text clipped - 28 lines] > > > > > > Martin Folb Responsive during cold start. Runs like normal up to 4-5000 rpm. Then dies once 2 minutes have passed and the idle drops to 900 rpm. I tested the relay and pump for operation. They seem fine. When I raise the air flow sensor plate the pump goes on. > Martin - > [quoted text clipped - 23 lines] > > > > Martin Folb Turns out it was a faluty CDU unit. Im getting a Permatune. Thanks all for your help. Martin > I have a 78 911SC with 70000 original miles. It has never given me a > days problem for years until yesterday. After driving 10 miles, I [quoted text clipped - 11 lines] > > Martin Folb If it the CDI unit it is probably a cold solder joint. You can have the unit rebuilt. > Turns out it was a faluty CDU unit. Im getting a Permatune. > [quoted text clipped - 17 lines] > > > > Martin Folb 2 Questions: what's a CDU unit and what's a CDI unit? Usually CD stands for Capacitive Discharge and it's a module/unit. At least that's what DartAuto.com calls it: Permatune CD Units for Porsche 911 It's not a "Capacitive Discharge unit unit". What's a CDI? Capacitive Discharge I? What's the "I"? Capacitive Discharge is exactly what it sez,i.e., a blocking oscillator, etc. is used to store a high voltage on a capacitor and then discharged via an SCR to deliver 0.5 joule to the spark plug. The attack time of the spark is measured in microseconds and the voltage doesn't get a chance to leak away through oily deposits on the plug's center ceramic post. Just very confused by the terms and want to learn. > If it the CDI unit it is probably a cold solder joint. You can have the > unit rebuilt. [quoted text clipped - 22 lines] > > > > > > Martin Folb Username munged by FixNews CDI Capacitive discharge Ignition > 2 Questions: what's a CDU unit and what's a CDI unit? > [quoted text clipped - 5 lines] > > Capacitive Discharge is exactly what it sez,i.e., a blocking oscillator, etc. is used to store a high voltage on a capacitor and then discharged via an SCR to deliver 0.5 joule to the spark plug. The attack time of the spark is measured in microseconds and the voltage doesn't get a chance to leak away through oily deposits on the plug's center ceramic post. > Just very confused by the terms and want to learn. > [quoted text clipped - 29 lines] > http://www.newsfeeds.com - The #1 Newsgroup Service in the World! > -----== Over 100,000 Newsgroups - 19 Different Servers! =----- Thanks, I should have known that. Sigh... > CDI > > Capacitive discharge Ignition > > > ... what's a CDI unit? Username munged by FixNews for what it's worth, I have an article on building your own CD ignition on my web page, www.home.labridge.com/~wnoble > Thanks, I should have known that. Sigh... > > > CDI > > > > Capacitive discharge Ignition |
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