Cold starting issues

[camelotr]

Hello,

Now that the temperature lowered, I have cold starting problems. The car only starts after long cranking, with some movement of the gas pedal. Still it is running rough and apparently very rich.
I checked the fuel pressures.
- system pressure: 6.4bars
- control pressure cold (17degrees): 1.2bars
- hot pressure: 3.7bars

These values look correct for me. What else can be the problem?

[smurfbus]

You can try to adjust co crew small steps to see if it helps. Normally colder means more air and leaner but the wur cold circuit may be affected for more fuel too?

[Dmitry at Pelican Parts]

Originally Posted by camelotr

Hello,

Now that the temperature lowered, I have cold starting problems. The car only starts after long cranking, with some movement of the gas pedal. Still it is running rough and apparently very rich.
I checked the fuel pressures.
- system pressure: 6.4bars
- control pressure cold (17degrees): 1.2bars
- hot pressure: 3.7bars

These values look correct for me. What else can be the problem?

Check out this tech article on starter issue. I hope it'll help you resolve the issue.

Porsche 911 Starter System Troubleshooting | 911 (1965-89) - 930 Turbo (1975-89) | Pelican Parts DIY Maintenance Article


-Dmitry

[camelotr]

Originally Posted by Dmitry at Pelican Parts

Check out this tech article on starter issue. I hope it'll help you resolve the issue.

Porsche 911 Starter System Troubleshooting | 911 (1965-89) - 930 Turbo (1975-89) | Pelican Parts DIY Maintenance Article


-Dmitry

Many thanks for Your help Dimitry. Unfortunately my problem is a bit more complex.
I now set the wur up, so that it starts the car 99% on the button, no matter how hot or cold is the engine.
Only one time do I suffer from hard starting: the very first time in the morning. When I try to start it the starter is working at speed, the engine turns over as it should, we have spark (at least when I remove the plug, and put it against the engine, it works), but the engine will not start. Just when You release the key, it is likely to start, sometime not. But after 3-4 attempts of cranking-releasing the key, the engine will start. Of course it will suffer from fuel overload (the cold start valve did its job properly), and the car will smoke blackish for a few sec, but after it, it will clear up and the idle will settle.
After this, the car will start any time on the button for the whole day. No matter how long I leave it undisturbed.

[911nut]

You may have a bad thermotime switch that isn't enabling the cold start injector.

[T77911S]

the TTS is a good check. also check wires on starter. the CSV gets its power form the starter
you really need to state the year but based on your pressures it looks like you have non-lambda.
17degrees I take it is CEL.

a tune up can help.
turn the key on and push down on the mixture adjustment for 2-3 seconds then start it.,
mixture might be too lean.
air leak making mixture lean

[camelotr]

Ok. Thermo switch is working. BUT while I removed the connector of the tts, and asked a friend to turn the ignition key, the engine fired up instantly . This engine is getting more fuel, not less than it needs. I am a bit puzzled...
It is 17 degrees (62.5F) now in the workshop. Cold control pressure is set even a bit higher than factory spec (1.6 bars instead of 1.0-1.4bars), which should result leaner condition than normal. Still...
On the AFR is around 11 when cold, and lowers to 13.6-13.8 when hot at idle.

From what temperature should the tts activate the cold start valve?

[camelotr]

Originally Posted by T77911S

the TTS is a good check. also check wires on starter. the CSV gets its power form the starter
you really need to state the year but based on your pressures it looks like you have non-lambda.
17degrees I take it is CEL.

The engine is '87 EU spec (no lambda), and yes 17 degrees is Cel, eq to 62.5F. Sorry for missing that.

[RarlyL8]

CSV should activate below 45°. Verify the CSV is not leaking or firing at a higher temperature. After that verify your injectors are not leaking.

[JFairman]

The CIS or k-jetronic TTS has an internal thermostat that heats up and should disable it after cranking the starter motor for more than a few seconds so the motor is not flooded.
Sounds like that function is not working on yours and it may be spraying fuel continuously every time the starter motor is cranked. If this is happening the motor will be flooded with way too much fuel after 3 to 5 seconds of starter motor cranking.

A simple low cost work around if you don't want to buy an expensive new TTS is just disconnect it from the starter motor power completely and wire the CSV to a generic engine starter button from an auto parts store. (Some of those are cast aluminum and look pretty nice and some have a water proof rubber cover over the button so they can be installed in boats or equipment that get rained on regularly)

Then to start the motor when it's cold hold down the generic starter motor button for a second or two while cranking the starter motor and it should start.
If the motor is warm do not touch the new CSV button you installed because the motor does not need the extra fuel to start.

When I worked at a street car shop on BMW's in the eightees we used to do this on CIS BMW 320i's when the TTS went bad and the customer didn't want to spend the money on a new one.

FWIW, you could also install the manual CSV activation button in the spoke of an after market steering wheel and hold it down with your thumb for more fuel injected into the intake manifold under the throttle body during high rpms and boost if the motor can use more fuel.