Reinstalling oxygen sensor system

bsimonson · bsimonson's Garage

Hi!

I'm new to this forum and also to Porsche ownership. Nevertheless I've bought a US 1980 911 SC and I really like it! I have just started a blog, only one post so far but a least there are some pictures of it there.

My plan is to drive it as much as possible this summer and come fall I will attempt more serious work on it, whatever needs being done.

But before I can enjoy it I need to reinstall the oxygen sensor system as the previous owner made an attempt to convert the fuel injection to euro-spec, only to realize at the last moment that the new metering head he planned on using did not fit. I decided to buy the car anyway as I can get good help with electrics from family and also has some experience myself.

I've read a bit about the O2 sensor system on this forum and in the Bentley book. I won't be able to connect the oxygen sensor itself because the car has an SSI exhaust but I need rest of the system to control the frequency valve.

Spent some time in the garage today trying to refit the wire harness for the temperature/throttle switches and FV. I'm not sure on how to route the wire for the temperature switch as it is quite short when the other connections are connected and I don't want it to near the really warm parts. And I can't find where to fit the six-pin connector on the harness at all. It might have been cut out but I'm not even sure where to look for it. This is the one I mean:

Any advice or pictures of how it is supposed to look would be very helpful!

Cheers, Björn (from Sweden)

psalt · 06-12-2010, 09:05 AM

Hello Bjorn,

Welcome to the list. The plug goes to a jack near the left side shock tower. The wire to the temp switch on the right chain case snakes around #4 & #5 intake runner, then cuts across the top of the fan shroud under the airbox.

grahamkissack · 06-12-2010, 10:57 AM

Paul (Psalt) sent you a pm.

Thanks, Graham

don gilbert · don gilbert's Garage

Smart thing to do Graham, hooking it back up. I have an 02 with ssi, get the bung at any parts store and drill hole and weld it on. You can get a Bosch one wire at most stores for under 20 bucks. Your engine will like it, your fuel mileage will go up, and drivability will be much better below the 35 degree throttle switch. Is the ecm still under the seat, As Paul said, the conn. is behind your blower motor by rt shock

bsimonson · bsimonson's Garage

Wow guys, great replies, thank you! I'm a bit busy today but will have a look at it tonight I hope.

I have the control box that's under the seat and also the relay, but not the box that's right next to the big box in your picture Don. Is that related to the O2 system? If it's an 81-83 model maybe it is the cold acc. CU?

Also, I don't have the original wiring from the box to the rear plug so I will have to make a new harness for that.

I'm also pretty sure that the test connector contacts are no longer where they should be. Looking at the wiring diagrams in the Bentley book I can see no real reason to have them at the back rather than under the passenger seat. Wiring the ground to G2 seems a lot easier than going all the way to the back, but maybe I'm missing something?

/björn

don gilbert · don gilbert's Garage

That is a cold weather enrichment device, only on 82-83 cars. (your not missing anything, that thing is worthless)

bsimonson · bsimonson's Garage

Going out to the garage straight from work today do to the bulk of the installation. I looked one more time at the wiring diagrams this morning and realised that there is one connection to the warm-up regulator / control regulator (depending on what diagram you look at - the one in chapter 2XX or the one among the other wiring diagrams at the end of the Bentley book).

The thing is that that wire is not part of the harness I have, so how/where do I connect that wire to the regulator? Maybe it is obvious when I look at it IRL but any descriptions to aid my work would be much appreciated.

Cheers, Björn

bsimonson · bsimonson's Garage

Some progress has been made with the install so I've put up a post about it in my blog.

Decided to have the test connectors under the seat rather than in the back, I guess time will tell if that was a good or bad decision.

Cheers, Björn

bsimonson · bsimonson's Garage

Great day today, I was able to start the engine with the O2 system connected for the first time! Still need to route the wires to the engine through the rear wall but nice to know that everything is OK.

One question: The wiring diagram in the Bentley manual had the red (power) wire for the test connectors routed from fuse 22, which does not exist in my car (only up to 21). Any ideas where it is supposed to go? Not critical at this point but nice to have when I find someone who can dial in the system.

Some more pictures in my owning a 911 SC blog

psalt · 06-19-2010, 09:19 AM

when I find someone who can dial in the system....

Find an old analog dwell meter, read the archives, then look in the mirror.

bsimonson · bsimonson's Garage

Quote:

Originally Posted by psalt

when I find someone who can dial in the system....

Find an old analog dwell meter, read the archives, then look in the mirror.

lol, yeah that sounds like a plan. Will probably need to adjust the mix too, as I don't know the status of that at all. So, if whoever I find to do that can do both, I'll let them, otherwise I'll give it a shot myself.

bsimonson · bsimonson's Garage

Finally got the time to finish the oxygen sensor reinstall. Posted a few pictures in my blog about owning and driving a 911 SC.

The car runs but is a bit hesitant when cold (didn't run it for long so not sure about when it is hot) and I can smell fuel at times, so as some people have mentioned it is probably a bit rich. I intend to get a proper adjustment with a exhaust measurement but I would like to make a bit of an adjustment before that. What would be a good start, is half a turn CCW to much? I have no experience with adjusting the mixture so any advice is welcome.

Cheers, Björn