Help with cold start issues

[Mike80911]

Hello everyone I have a 1980 911 SC that has a cold start problem as you can see by the video when the car is cold and I start it the engine will sputter and die when I try to give gas it will pop and sputter It starts right up when I turn the key but will not run as you can see in the video it will run when I give gas but even with my foot on the pedal and the RPMs at 3000 it will just die. Any advise on causes would be helpful I am having trouble finding anyone who wants to touch it around here no one wants to work on an SC everyone wants to work on the newer models. If there is anyone nearby who wants to come help I will gladly pay you for your time and knowledge. Thanks for any help
Mike



Direct Link:

http://s249.photobucket.com/albums/gg230/1996softail/?action=view&current=IMG_0299.mp4

[Mike80911]

I can't get the video to work directly so please use the link to see it thanks

[bfunke]

I'm no expert on FI but I would check the cold start valve and the control pressure regulator. Also be sure your filters aren't clogged.

[Walter_Middie]

Mike,

You don't mention how it runs after it warms up.

Typically, your running issues are caused by vacuum leaks and/or the WUR is not supplying the correct amount of fuel for the temperature the engine is at.

You can diagnose by yourself, but you'll have to invest in some tools, such as a CIS fuel pressure tester:

Pelican Parts - Product Information: TOL-TA33865

This tool, and the Pelican brain trust, can tell you what part of your CIS needs attention.

If you would rather have a professional mechanic look at it, someone one this board will most likely recommend a local NY mechanic that can work on these cars. I know when I first got my car, I was surprised to find that a regular mechanic or the dealer would not even want to get near my car. I even found a foreign car repair place with supposedly ex-Porsche mechanics - after seeing some of their work, I wouldn't let them even wash my car.

One of the nicest things about these cars is the fact that there are small repair places that specialize in air-cooled Porsches, and provide excellent service. The only problem is finding them. Once you do, you are set.

[pete3799]

May be a combination of timing and fuel mixture.
The popping sounds like a timing issue.

[Mike80911]

Walter it was running decent when warm but now it seems not to run good even when warm I checked for vacum leaks when I spry near the WUR the idle goes up but I do not see any vacum lines in that area maybe it is just getting sucked into the air cleaner I am not really sure. It stalls every time I come to a stop when driving now also. If I am not mistaken the cold start valve supplies fule to start the car only and as I said the car starts right up after turnung the key and waiting a second then starting so that should be functioning properly right?

[pete3799]

Should be at least one vacum line going to the WUR some have 2.
See if you can get it to idle by turning the idle screw. It's to the right of the throtle linkage
the head of the screw is about the size of a dime. Once you get it idling, unscrew your oil fill cap and see if your idle drops. If not you have a vacum leak somewhere.

[Bob Kontak]

Do you have an oxygen sensor? It may be the relay, if so.

[Mike80911]

Pete thanks for that advise I think I saw the idle srew back towards the rear of the CIS with the large head and the spring is that correct I will try that tomorrow and see what happens but I cannot see any vacum lines on the WUR just 2 lines that look like pressure lines and the wiring that is all I see and as for an O2 sensor there is a dash light for it but I have not looked underneath to see if it is in fact there yet.

[pete3799]

Counter clockwise to increase idle. 950 RPM is were you want it.

[Bob Kontak]

The relay is under the passenger seat. Hooked onto the big box. You don't have to remove the seat to get to it.

Take it out and examine the contacts - the wires can push back into the female connector.

You can read this thread for more info and if you wish read how you can jumper the the middle posts on the relay and plug it back in to test if it is your problem.

911 SC running "flat" and no idle

This is a $13 fix for a new relay so worth you time to review.

[Mike80911]

I will check that also tomorrow thanks Bob

[Walter_Middie]

If I am not mistaken the cold start valve supplies fuel to start the car only

This is correct - if your engine starts right up, the cold start valve is most likely working. It only adds extra fuel while the starter is energized. As soon as you let the key spring back from the start position to the run position, the cold start valve quits.

[boyt911sc]

Mike,

If you have the time and interest to do the CIS troubleshooting for your car, there are plenty of help available in this forum. All you have to do is give us a good information about the problem/s and feed back to some suggestions. If the car was running before and gradually deteriorated to difficult to start, something has changed.

At this point, do not touch or play around with the mixture screw!!!! You'll make a bad situation worst. You have ignition (sparks), compression, fuel and air as demonstrated by the video. The question is do you have the right amount of fuel (pressure) and air (metered) to sustain the combustion?

Most lean condition problems in CIS is not the lack of fuel but too much air due to air leak (vac). Use a fuel gauge to check your control and system pressures. Next pressurize the system for air leak/s. If the car was running OK before and gradually deteriorated to a point that it is not starting or running any more means something has changed to cause this effect.

Could you post a picture of the WUR and its connections? Your problem is minor and easy to solve. Lastly, do you have power to the interior and glove compartment lights ? Keep us posted.

Tony

[Mike80911]

Thanks Tony I will take a pic of the WUR and post it tomorrow during the daytime since I bought the car it has had this cold start issue but now it has gotten worse I replaced the plugs, cap and rotor did the plugs and cap change one at a time so as not to screw up firing order and set the plugs at .28 as per the Haynes manuel The car was converted to a convertible way back in 83 so the inteior lights are not there as for the glove box I will check is this all connected to a certain circuit that might have a bad fuse?

[millhaus]

I just rebuilt my 930 and had a similar issue. Try adjusting the mixture more rich (clockwise) and see if it starts. you may have to turn the adjustment screw quite a bit. Keep trying and see if it gets any better (I.e. less RPMs needed to get it started or keep it running)

More than likely you have a vacuum leak in the CIS system or as mentioned one of the many parts (WUR, Aux air valve) not working properly.

Good luck

[pete3799]

I wouldn't fool with the mixture just yet till you figure out the problem.
As Tony stated you need to check for vac. leaks and check your fuel pressures (warm & cold)
before you start messing with the settings.

[Bob Kontak]

Originally Posted by boyt911sc

Lastly, do you have power to the interior and glove compartment lights ? Keep us posted.

Forgot to mention that symptom in my O2 relay post - Thanks Tony.

[boyt911sc]

Originally Posted by millhaus

I just rebuilt my 930 and had a similar issue. Try adjusting the mixture more rich (clockwise) and see if it starts. you may have to turn the adjustment screw quite a bit. Keep trying and see if it gets any better (I.e. less RPMs needed to get it started or keep it running)

More than likely you have a vacuum leak in the CIS system or as mentioned one of the many parts (WUR, Aux air valve) not working properly.

Good luck

millhaus,

Meshing with the fuel mixture will only add more variables to the current problem/s!!!! Leave it alone and fix the cause of the problem (vacuum leak). Testing the other CIS components as you suggested is a good one to follow.

You could simply test for air leak/s and stop guessing. If the pressure test shows that there is minimal pressure drop and could maintain a positive air pressure for a while, then the system is in good condition. Once you have confirmed that the engine is air-leak free (which is very difficult to achieve), you have eliminated one variable from the problem. Then focus next on the fuel delivery system.

The sudden change to 'too lean condition' in CIS is not the lack of fuel but the presence of extra air (unmetered) in most cases. The FP is easy to check. But if people doing the diagnostic use the right procedure to determine the cause of the lean condition, test result will lead you directly to the root cause of the problem. HTH.

Tony

[Nick Triesch]

THIS HAPPENED TO MY FRIENDS 85 911 AND AFTER MUCH TESTING, IT TURNED OUT TO BE THE BRAIN. aFTER A NATION WIDE SERCH, HE FOUND A USED ONE FOR $700 AND INSTALLED IT AND CAR STARTED AND WORKED PERFECT FOR MANY YEARS. NICK