O2 (Lambda system) relay question??

RickKlem · 06-09-2003, 05:28 PM

I'm installing a 80 3.0L into my car and I had to install the Lambda (O2) stuff. I found a wiring diagram for this system and it shows a " relay" connected to the frequency valve. It also connects to the wur. Does anyone know if I need this relay or is it already on my car 1977 2.7 911?

If I do need it what is the part number?
Thanks
Rick

mb911 · mb911's Garage

You definitly need it as it operates the frequency valve. Feel free to contact me any time you like I have done the same project and can tell you my nightmares (ongoing)
bimn@genevaonline.com

Ben
77 911 81 3.0

78targa · 78targa's Garage

I don't have the part number for the relay readily available, but I can get it this weekend for you.
It should be located next to the Lambda unit under the passenger seat. It is the little black square box with a single mounting hole in it.

Yes, your car will not run properly without it.

Do a search on this board for "Lambda Frequency Valve." I did an engine swap from a 1980 to a 1978 (and vica versa) last month. I tried really hard to pry the Lambda portion from the engine, but in the end the most economical solution was to transfer it over. What a pain in the @#^%!@#^ .

John Walker was very patient in his explaination as to what mods I would need to perform in order to remove it. I think the post covered the options fairly well, in case you are interested.

If you have any questions involving the transfer, where the system hooks up, ask away as it is still fresh in my mind.

78targa · 78targa's Garage

Go figure, I just remembered I have a copy of the receipt in my desk.

Pelican part# 821-951-253 (0-332-019-150) Oxygen Sensor Relay (80-89) 911

Last year's price put it at $11.20.

RickKlem · 06-13-2003, 03:25 AM

Casey and Ben

Thanks so much for the info, I ordered one today from our host. Also thanks for the offer of technical support on this adventure. I may take you up on the offer.

Regards
Rick

mb911 · mb911's Garage

Casey,

What exactly does that relay do you spoke of? I thought we were talking about the frequency valve relay which is the small 1X1 realy that really does not have a mount. This part on my car is in question because my engine swap has not gone so smoothly. The car starts fine and runs fine not under load but if you give it the gas it it kind of takes of like my wifes minivan versus what it should. Does this relay cause enrichenment?

RickKlem · 06-13-2003, 04:43 AM

Ben

I think that it supplies power to the control box for the lambda system which is located under the passenger seat , this is where the relay would be located as well.

I only know this because of info that I obtained from the PelicanParts folks. But I'm not an expert, I'm leaning about this stuff myself. Lets wait and see what Casey has to say.

Rick

john walker's workshop · 06-13-2003, 07:35 AM

without the freq valve functioning the system goes way rich, and the car feels like it's dragging an anchor. the relay plug would be in the lambda wire loom, which would be the best way to do it, rather than fabbing a loom.

Lorenfb · 06-13-2003, 07:46 AM

The Porsche CIS unit has two relays, a small 1X1 used to power
the CIS unit and the freq. valve. The larger 1X3X3 is the fuel
enrichment relay. The sensor plate switch energizes the small
relay just like the fuel pump relay once the engine runs.

Get a good wiring diagram.

Good luck
Loren
Systemc.com

mb911 · mb911's Garage

What do you experince when the enrichment relay does not work? I believe mine is junk. It looks to have water damge and does nothing pluged in or not. I can tell you the frequency valve works fine and all the fuel pressures are perfect. The car goes like a vw rabbit versus what it should. Could this be my problem? What exactly are the symptoms that I would be looking for? The lambda brain appears to function as a definite difference when pluged in or not. I think this might be the last peice in my huge jig saw puzzle. If this is my culpret where can I get one at a reasonable price?

Thanks
Ben

78targa · 78targa's Garage

Well I guess everyone beat me to a reply on that one. All said it better than I ever could!

Ben, look earlier in this thread as I posted the part number and price from our host for the relay.

I like John's description of what happens when one of these components stop working: "car feels like it's dragging an anchor."

These things can fool alot of people. Two car owners back on my 911 had the relay by the Lambda unit go out. They replaced plugs, plug wires, alternator...a whole mess of things. Decided to dump the car because they thought it was getting ready to die! The guy I bought the car found the problem in the relay and fixed it for a little over $10.

Lots of problems from a failure of such a small part.

78targa · 78targa's Garage

John,

If you are still looking over this post, I have a question. Would the frequency valve function at all if this relay was bad? I would think if the relay was not working then the frequency valve would not be modulating.

Is the default way to check proper function just to reach behind the CIS and grab the valve to see if it is vibrating?

Of course if it isn't getting power the dome light circuit should be checked as well.

mb911 · mb911's Garage

Casey,

The part number you gave was I believe for the frequency valve relay. I called pelican today and they said the other relay was $190.00 bucks. I took mine apart to see what it was all about and it basically is a circuit board with some prom chips in it etc. I did just replace that relay and worked perfect after that. But the car just dos not seem to go like it should. It revs up fine and cruises fine but never rips like one would think. My 914-6 would kick its a@#. As far as the relay we are talking about the one that is bolted to the lambda brain and is the larger of the two relays next to the brain?

Thanks
Ben

78targa · 78targa's Garage

Hmm,

I only have one relay next to my brain. It is the $10 one. The engine is from a 1980. Might that be the diference. I am not sure about the expensive relay you referred to.

You mentioned that you car drove like a dog at high rpms. Have you checked the advance on your distributor? Should be advanced 5 degrees at idle and 30 to 35 (no more than that) at, I believe, 5000 rpms.

If your spark isn't advancing properly that could cause your high end power loss rather easily.

Lorenfb · 06-13-2003, 08:57 PM

The enrichment relay provides max. accel when you "hit" the
throttle. W/o it, the car will probably be your VW Rabbit.
Get a new relay and find the water leak.

Good luck
Loren
Systemsc.com

mb911 · mb911's Garage

Thanks guys I am going to to get a new relay. As far as the water leak it must of been in the shed where the engine was kept before I bought it. you might remember this was the engine that was suppose to be a good runner(ebay) . Well it wasn't; new head,valve job,rings,head studs, ignition box, and whole mess of odds and ends. This is the last chapter of my nightmare.
Thanks
Again
Ben

mb911 · mb911's Garage

Ok update . I just adjusted timing as it turns out it was retarded. The car now will get pretty sideways and takes off well but still concerned about that relay. Can anybody tell me how to test it to see if it works?

Thanks
Ben

Bart911Man · 06-14-2003, 02:28 PM

Hi mb911,

I have a US '80SC.

Since this O2 sensor / relay stuff didn't make lots of sense to me I had my lokal mec (an early Porshe Goeroe) tune the engine with the O2 sensor disconnected and the relay out.

He ensures me that my car is the fastes SC he ever drove (stock engine except for the tuning). Next thing is a lambda bypass and other exhaust optimisation.

Bart.

mb911 · mb911's Garage

I have thought of backdating to the earlier SC CIS but really would like to get this operating correctly. I still think my 914-6 would take it but the car seems much better. I pulled the plugs and they still look lean and I think it has to do with the relay.
Ben