Cold Start Issue 79SC

[Johnb911]

I have read more than enough threads to be confused.

here is the issue

Took out motor.
New hoses, gaskets etc on CIS.
Valve Adjust.

Put back together.
No Leaks that I can find.
Pull the oil cap and it starts to stumble.

Won't cold start unless I prime with the sensor plate.
Runs after that.
Needs AFR adjustment.

Fuel pump DOESNOT run when I tur on the key.
Injectors fire when I lift the plate when key on.
All connections are connected. Right I think.

It always always started in about a full crank without any peddle.
Perfect as perfect.
Idle high for a minute then settle down to 950 ish.

I know you are going to say check pressure.
i don't have a set of gauges right now.
Can we assume it's fine for now as it obviously must have been before.

What else could it be?

If I have the connection on the cold start valve mixed up with something else on the back of the motor could this due it?

HELP.

[psalt]

Fuel pump DOESNOT run when I tur on the key.

Hello John,

This is normal, fuel pump should not run with the key in the ON position unless the engine is running and lifting the air flow sensor. You are on the right track, troubleshoot the cold start valve circuit. The CSV gets power from the starter when cranking, the ground comes from the Thermo time switch. Try grounding the wire at the Thermo time switch, then attempt a cold start. The CSV is only relevent when cranking, the TTS is there to prevent flooding from too much cranking by disconnecting the ground circuit. Keep this in mind when testing.

[T77911S]

If I have the connection on the cold start valve mixed up with something else on the back of the motor could this due it?


my first thought was yes. but as i think about it. all the connectors have 12v on them and they would keep the CSV on all the time, making it run very rich. good cold start, bad warm running, unless you adjusted the mixture.

check power to CSV as said above. i would pull both wires off the thermo time switch (TTS). one side is 12v to heat it up. the other is the 12v from the CSV. remove the wires to isolate and not get a false reading.
one will have 12v all the time, the other when starting. you need 2 people.

[kmhemi]

I had the same problem. I had a broken connection in the plug for my cold start valve. I relpaced the plug and now its fine. I'd check the cold start valve plug and the one on the back by the air sensor plate they might have gotten mixed up. and check the voltage at the CSV.

[Johnb911]

Thanks guys.

Im sorry but the CVV is on the drivers side chain housing correct.
I will try this Sunday after my weekend list is complete of course.

[ruf-porsche]

Originally Posted by psalt

Fuel pump DOESNOT run when I tur on the key.

Hello John,

This is normal, fuel pump should not run with the key in the ON position unless the engine is running and lifting the air flow sensor. You are on the right track, troubleshoot the cold start valve circuit. The CSV gets power from the starter when cranking, the ground comes from the Thermo time switch. Try grounding the wire at the Thermo time switch, then attempt a cold start. The CSV is only relevent when cranking, the TTS is there to prevent flooding from too much cranking by disconnecting the ground circuit. Keep this in mind when testing.

Hmmm strange I can hear the fuel pump run for about 2 seconds when I turn the key to the on position.

[Johnb911]

I meant continue to run.
I had read in a thread that if you have some of the plugs mixed up on the CIS this may happen.

[psalt]

Hmmm strange I can hear the fuel pump run for about 2 seconds when I turn the key to the on position

You might be hearing the CDI. Some EFI ECU's do this, but what part in an CIS 911SC could do this ?

I had read in a thread that if you have some of the plugs mixed up on the CIS this may happen.


The CSV is triggered by the ground connection, mixing up the plugs gives you no CSV. The Thermo time switch heater does not get 12 volts all the time, it is powered by the same yellow wire as the CSV, which has 12 volts only when cranking. The TTS is on the left side chain cover, the CSV is behind the airbox, a mirror helps to see back there.

[Johnb911]

Didn't have achance to check the yellow wire yet but found something else.

When I started the car tonight I went to the fron and noticed my battery was bubbleing a little.

Not cool I thought.

checked voltage 19.5

Can I assume I have a bad regulator?

Mine is on the side of the engine bay.

Can I check this thing to confirm somehow?

[Mysterytrain]

I think you should make sure the cold start valve electrical connection is correct I believe that connection can be easily mixed up and create issues. The cold start valve also needs a good working thermo switch and connection [ located on the left chain cover ]. The switch provides ground in the cold start injector circuit.
Also check that the fuel cutoff connector is plugged into the switch, if not the fuel pump will run as soon as you turn the key...not good.

[ruf-porsche]

Originally Posted by psalt

Hmmm strange I can hear the fuel pump run for about 2 seconds when I turn the key to the on position

You might be hearing the CDI. Some EFI ECU's do this, but what part in an CIS 911SC could do this ?

I had read in a thread that if you have some of the plugs mixed up on the CIS this may happen.


The CSV is triggered by the ground connection, mixing up the plugs gives you no CSV. The Thermo time switch heater does not get 12 volts all the time, it is powered by the same yellow wire as the CSV, which has 12 volts only when cranking. The TTS is on the left side chain cover, the CSV is behind the airbox, a mirror helps to see back there.

Nope the sound is coming from the front where the fuel pump is located, not from the back where the CDI is located.

[boyt911sc]

Originally Posted by Johnb911

Thanks guys.

Im sorry but the CVV is on the drivers side chain housing correct.
I will try this Sunday after my weekend list is complete of course.

John,

That's the TTS on the driverside chain housing. CSV is located at the backside of the engine just below the throttle body.

Tony