1981 911 SC newbie cold start problem

[SanDiegoMike]

Hello! This is my first real post so bear with me. I have a 1981 911 SC. I found out early this morning that it had a major cold start issue. I warmed it up for a few minutes but as I went to shift and give it gas it would sputter and die like the gas pedal was not being pushed. The PO says he was setting the car up for autocross and disconnected the choke? I am not sure that makes sense but am here to learn. The fuel injectors also need to be cleaned or replaced. This car was a gift from the owner for a real estate deal I did not take a commission on. He showed up and dropped it off to me so no pre sale inspection. I am going to check the forum now but would appreciate anyone pointing me in the rite direction. Looking forward to meeting everyone and learning this car!

[Bob Kontak]

Hi Mike,

How do you know the injectors need cleaned?

Does it sound "decent" when the car idles?

There is no choke on an 81. There are throttle air bypass components. Can you take your cell phone and shoot a pic of the right side of the engine - take a pic or two of the plumbing and hoses and such on that right side. "Go Advanced" and figure out how to upload these pics after you send them to your e-mail and save them on your computer.

One thing at a time. You also may have odd fuel pressures and you will be urged to buy a set of pressure gauges. You will need them if you are interested in maintaining the car. Vacuum leaks are also a big issue with CIS.

Also, try idling the car for 20 minutes and see what happens.

[GaryR]

Mike, as you got it for "free" I would suggest taking it to a good shop (ask here for recommendations) and have them go through it. It could be fuel, could be electrical, and it's a bit much to bite off for your first project. I will say it isn't a "cold start" issue as it started cold, then ran badly. If the cold start system wasn't functioning it simply won't start well (if at all) when cold.

Once you get the car running properly take on small projects so you can enjoy the car in the meantime. Just my $.02.

[blyguy]

Hi Mike, I'm local and can help out. I went through the same thing with my 83 SC. Some things to check first are the fuel supply - filter and pump need to be ok. How does the car run when warmed up? If its a purely cold start issue (which in San Diego means 55-60 degrees F haha) you can start with the (warm up regulator) WUR and fuel distributor adjustment. It takes some fiddling around and having a pressure tester is key to diagnosing the WUR.

Shoot me a PM if you'd like

Bryant

[tom1975]

Disconnect the o2 relay under the passenger seat,
If you don't have rpm change it's probably the relay.
Buy one for $ 10
And you solve the problem,
You must bosche relay no:
0332019150
Carefully look and read this thread:
81 SC Oxygen Sensor Relay
Good luck

[Bob Kontak]

Originally Posted by tom1975

Disconnect the o2 relay under the passenger seat,

Your advice kicks major ass, but only if it's the problem.

You sure it's the problem based on the input? Seriously?

[SanDiegoMike]

Thanks everyone.
Bob- PO said that the shop he had taken it to recommended replacing the fuel injectors. I will take pictures in the morning and upload all. After 20 minutes the car idles nicely. It lacks the power I have felt in others cars I have driven at higher RPM. You can put the pedal to the floor and just get a slow steady acceleration. When you step on it you just don't get much of a response. Do you recommend any brand of gauges?

Gary- I met a gentleman at cars and coffee that a lot of guys in the Porsche o club use. He can look at it on Monday. Agreed, not a good first project. On another note, the battery died today. When AAA came out they said it was 8 years old and replaced it. After they tested the system and told me the alternator is not charging the battery. I might have to tackle that first.

Tom - Thanks for that. The PO gave me a few boxes of parts and there was a box that had a relay for the O2 sensor.

Thanks everyone for taking the time to reply. I will post any results.

[timmy2]

A bad alternator can cause poor cold starts. Injectors may only need o-rings and cleaning.
Lots to do with a new to you car and not a lot of maintenance history.

[SanDiegoMike]

Thanks for the input Tim. There will be a lot to learn on this one. I was a 944 guy before and this is a totally different beast. Looking forward to learning. I am pretty sure I will have a few ouch moments

[tom1975]

Originally Posted by Bob Kontak

Your advice kicks major ass, but only if it's the problem.

You sure it's the problem based on the input? Seriously?

hi
Yes i am serious , cold problem and bad performance 99% it's the o2 relay .
I am of course talking about my experience, I had a similar problem.
The reason I suggested checking the relay is that the test is very simple, inexpensive (only 10$)
Worth to do it before starting to dismantle half the vehicles and spend large sums on replacement parts do not always need to be replaced.
This relay has many influences on the behavior of the engine from problems with the cold start to the bad performance of the engine.
good luck

[timmy2]

Welcome aboard SanDiegoMike,
Almost every question about these cars has been answered on this board.
Learning to use the advanced search is your best bet to get started.
Here's a good one for you :
Long term & Commonly Neglected Maintenance

[tom1975]

Thanks everyone.
After 20 minutes the car idles nicely. It lacks the power I have felt in others cars I have driven at higher RPM. You can put the pedal to the floor and just get a slow steady acceleration. When you step on it you just don't get much of a response.



Tom - Thanks for that. The PO gave me a few boxes of parts and there was a box that had a relay for the O2 sensor.


.

Change the relay !
I am 99% this is your problem
Make sure that the other relay in the box that you have from the po is good ,appropriate and functional
Check on the new relay diagram that the two 87 terminals connected like the original relay .Good luck

[boyt911sc]

Originally Posted by tom1975

hi
Yes i am serious , cold problem and bad performance 99% it's the o2 relay .
I am of course talking about my experience, I had a similar problem.
The reason I suggested checking the relay is that the test is very simple, inexpensive (only 10$)
Worth to do it before starting to dismantle half the vehicles and spend large sums on replacement parts do not always need to be replaced.
This relay has many influences on the behavior of the engine from problems with the cold start to the bad performance of the engine.
good luck

Tom,

The OXS does not come into consideration during a cold start and comes into play after the engine temperature gets close to 200°F. Second, the FV (frequency valve) could be tested without running the engine. If the FV is pulsating/vibrating during the FP test run, then the OXS relay is working. If you want to check the FV/OXS/ECU combo, use a dwell meter. Test and confirm.

Tony

[tom1975]

Quote de tom1975

hi

Yes i am serious , cold problem and bad performance 99% it's the o2 relay .

I am of course talking about my experience, I had a similar problem.

The reason I suggested checking the relay is that the test is very simple, inexpensive (only 10$)

Worth to do it before starting to dismantle half the vehicles and spend large sums on replacement parts do not always need to be replaced.

This relay has many influences on the behavior of the engine from problems with the cold start to the bad performance of the engine.

good luck

Tom,



The OXS does not come into consideration during a cold start and comes into play after the engine temperature gets close to 200°F. Second, the FV (frequency valve) could be tested without running the engine. If the FV is pulsating/vibrating during the FP test run, then the OXS relay is working. If you want to check the FV/OXS/ECU combo, use a dwell meter. Test and confirm.



Tony

Hi tony
So how you explain that I have a problem with cold start that every time when I start the car the engine turn off and a lot of backfire from the air filter comes out and I need to press and pump the gas pedal several times to make him work and after he warm it's work good but with less power on the Road ,I buy anew o2 relay and the problem solved !!!???
To make sure than I solv the problem ,After I replace the relay I take the old one and put him again and the problem come back , so it's not a Coincidence.

[timmy2]

Tom,
All Tony is saying is the OP should test and confirm what is and isn't working on his car.

What works for your car may not work on someone else's car. The systems controlling cold start idle are integrated as a system and without testing each component one cannot be sure which component has failed.

Some people have even fixed their relays instead of replacing them.

[SanDiegoMike]

Originally Posted by timmy2

Welcome aboard SanDiegoMike,
Almost every question about these cars has been answered on this board.
Learning to use the advanced search is your best bet to get started.
Here's a good one for you :
Long term & Commonly Neglected Maintenance

Great read!

[tom1975]

Tom,

All Tony is saying is the OP should test and confirm what is and isn't working on his car.



What works for your car may not work on someone else's car. The systems controlling cold start idle are integrated as a system and without testing each component one cannot be sure which component has failed.



Some people have even fixed their relays instead of replacing them.

Ok
By the way my ox sensor is disconnect I cancel it

[SanDiegoMike]

Originally Posted by Bob Kontak

Hi Mike,

How do you know the injectors need cleaned?

Does it sound "decent" when the car idles?

There is no choke on an 81. There are throttle air bypass components. Can you take your cell phone and shoot a pic of the right side of the engine - take a pic or two of the plumbing and hoses and such on that right side. "Go Advanced" and figure out how to upload these pics after you send them to your e-mail and save them on your computer.

One thing at a time. You also may have odd fuel pressures and you will be urged to buy a set of pressure gauges. You will need them if you are interested in maintaining the car. Vacuum leaks are also a big issue with CIS.

Also, try idling the car for 20 minutes and see what happens.

[schumicat]

red fan car in SoCal...did your car have a Motor Meister rebuild by chance? you may want to give it back (just kidding). the cold start system is fairly complicated...google Jim CIS primer and read up. if you can hear a buzzing when car is running (coming from behind the air intake housing) it means the frequency valve is working (part of the system with the 02 relay - if you can unplug that relay with no change the relay is probably bad).

[boyt911sc]

Mike,

In the last picture, is that Swage fitting set-up for the hydraulic chain tensioner? At first glance, I thought the engine was a 'turbo' with the solid heating tubes. Was the previous owner a plumber? Just kidding. Welcome to the club.

Tony