911SC Cold Hard Start issue

[Tk209]

Hi all

New to the forum and have search through a couple similar posts but nothing really matches my issue and of those that are similar, there seems to be no resolution.

Ive tried to upload a photo of the car, do let me know if it hasn’t work (posting from my phone).

My SC has a cold start issue. If it is completely cold it won’t start on its own, cranks fine etc but won’t get going. Bought this car in the summer and this has only come about with the cold(ish) weather. It’ll start up if I have previously lifted the air intake sensor plate (fuel pump does prime (whining sound)) or if I use some cold start spray. Once it starts the idle oscillates for a few seconds then it sits at about 1100, then down to 900 after about 2-3 mins. It then drives perfectly.

If I come to a stop and turn of the ignition it will never start first turn of the key, it will however instantly start on the second turn (providing the car is still relatively warm)

Battery is always on trickle so it’s strong and healthy.

Any ideas/advice?

[LIRS6]

Welcome -

what year?

here are some threads for your consideration:

https://forums.pelicanparts.com/porsche-911-technical-forum/1049314-cis-question-cold-start-valve-test.html

https://forums.pelicanparts.com/porsche-911-technical-forum/1042965-78-cis-cold-start-issue.html

https://forums.pelicanparts.com/porsche-911-technical-forum/1033806-persistent-cis-problems.html

Jason

PS - Search tool is your friend

[bluelectron]

Use the search function, there is lot of information on this forum. I had similar issues and may still have (will find out after the thaw) but your best bet is to buy a good set of CIS pressure gauges. I threw out a lot of money going to mechanics who did not solve the problem.

Other experts may chime in but I would begin with testing the fuel pump check valve and fuel accumulator.

[Tk209]

Originally Posted by LIRS6

Welcome -

what year?

here are some threads for your consideration:

https://forums.pelicanparts.com/porsche-911-technical-forum/1049314-cis-question-cold-start-valve-test.html

https://forums.pelicanparts.com/porsche-911-technical-forum/1042965-78-cis-cold-start-issue.html

https://forums.pelicanparts.com/porsche-911-technical-forum/1033806-persistent-cis-problems.html

Jason

PS - Search tool is your friend

Hi mate. Thanks for these. Year is 1983

[r lane]

Gauges are a must if you are going to work on this car. I would first test the coldstart valve and the thermo time switch. If they pass, then the check valve and on and on and if it is a lambda car, then more things to consider. Bob

[Johner]

Hi

It's worth getting the CIS gauges as suggested by others as without them you can't troubleshoot effectively. Don't skimp on these as the cheap ones can give erroneous readings and you can waste lots of time that way (I made that mistake). Systematically testing the components is key. The symptoms alone may indicate several potential causes so you need to eliminate them one by one.

It's also worth reading up as much as you can so you understand the basics of the system. CIS Troubleshooting for Dummies is really helpful as is the CIS primer linked in the early post of that thread. I think that has a troubleshooting guide which gives possible causes for different symptoms and how to test each component. There may be more than one thing going on which could explain why you can't find an exact match to your symptoms.

There are some simple checks of possible causes you can do without the gauges; cold start valve as linked above, thermotime switch and associated wiring can be tested independently and could be causing your problem. Also check the igntion components as they can also contribute to the problems.

There are plenty of people here who have been through this and will help you troubleshoot if you post the results of any tests you do.

Good luck

John

(By the way, your photo didn't post)

[Johner]

Hi

It's worth getting the CIS gauges as suggested by others as without them you can't troubleshoot effectively. Don't skimp on these as the cheap ones can give erroneous readings and you can waste lots of time that way (I made that mistake). Systematically testing the components is key. The symptoms alone may indicate several potential causes so you need to eliminate them one by one.

It's also worth reading up as much as you can so you understand the basics of the system. CIS Troubleshooting for Dummies is really helpful as is the CIS primer linked in the early post of that thread. I think that has a troubleshooting guide which gives possible causes for different symptoms and how to test each component. There may be more than one thing going on which could explain why you can't find an exact match to your symptoms.

There are some simple checks of possible causes you can do without the gauges; cold start valve as linked above, thermotime switch and associated wiring can be tested independently and could be causing your problem. Also check the igntion components as they can also contribute to the problems.

There are plenty of people here who have been through this and will help you troubleshoot if you post the results of any tests you do.

John

(By the way, your photo didn't post)

[Bob Kontak]

Originally Posted by r lane

I would first test the coldstart valve and the thermo time switch.

If the cold start function is working, you can have several things way off and the car will still start. There is so much atomized fuel delivered through the cold start valve that it is an EPA nightmare.

Start there.

[bluelectron]

Originally Posted by r lane

Gauges are a must if you are going to work on this car. I would first test the coldstart valve and the thermo time switch. If they pass, then the check valve and on and on and if it is a lambda car, then more things to consider. Bob

Any tips on how to remove the CSV. Almost seems like one would have to be a contortionist to remove it. I gave up after struggling for a while.

[boyt911sc]

Originally Posted by bluelectron

Any tips on how to remove the CSV. Almost seems like one would have to be a contortionist to remove it. I gave up after struggling for a while.

Blue,

It will be very helpful if you have seen how the CSV is installed on the airbox. The CSV is held by two (2) 5-mm Allen bolts and will need a 4-mm Allen wrench for removal. Get a long piece of string about 3 feet long and tape it to the 4-mm Allen wrench. Why? If you dropped the Allen wrench during the removal, you will be lucky to retrieve it. It would be there some where behind the motor. You will be spending more time looking for the missing wrench than the actual removal of the CSV.

This is my suggestion, get camera endoscope to help you do this job. It costs less than $50 to get a decent one and will pay for the first usage. A partial drop will help those guys with big forearms. I can reach and remove the CSV in situ simply because I have skinny forearms.

For testing the CSV, you will need a fuel line extension and electrical wires with connectors to conveniently test and observe the actual operation of the CSV. BTW, do not forget to look for the o-ring of the CSV. Keep us posted.

Tony

[bluelectron]

Originally Posted by boyt911sc

Blue,

It will be very helpful if you have seen how the CSV is installed on the airbox. The CSV is held by two (2) 5-mm Allen bolts and will need a 4-mm Allen wrench for removal. Get a long piece of string about 3 feet long and tape it to the 4-mm Allen wrench. Why? If you dropped the Allen wrench during the removal, you will be lucky to retrieve it. It would be there some where behind the motor. You will be spending more time looking for the missing wrench than the actual removal of the CSV.

This is my suggestion, get camera endoscope to help you do this job. It costs less than $50 to get a decent one and will pay for the first usage. A partial drop will help those guys with big forearms. I can reach and remove the CSV in situ simply because I have skinny forearms.

For testing the CSV, you will need a fuel line extension and electrical wires with connectors to conveniently test and observe the actual operation of the CSV. BTW, do not forget to look for the o-ring of the CSV. Keep us posted.

Tony

Thanks Tony, will try this after the thaw. Great tip on the string, I would have only thought of it after dropping the wrench.