CIS Troubles

[transformer]

I just cannot get my 1980 911SC to run right. It does not have power on acceleration so I checked the frequency valve and it is not buzzing. The resistance is 2 ohms and the connection is good. The car starts right up in the cold and does not stumble. Other than the bad acceleration the car runs great.

I bought a new OXS relay and noticed that it was not working and found fuse 18-5A blown, replaced the fuse and tried staring and the engine now takes longer to start and stumbles to stall.

I have replace the O2 sensor, thermo time switch, thermal switch, OXS relay and have tested the throttle switches, the O2 sensor, and they are OK.

The Frequency valve still does not buzz with the new OXS relay and I have run out of options.

[emcon5]

Does your dome light work?

Tom

[transformer]

I know the front trunk light does are they on the same circuit?

[emcon5]

Yeah, same fuse. Make sure the fuse didn't blow again, I had a defective OXS relay that shorted internally and would blow the fuse immediately.

Also make sure it is the correct relay, IIRC there is another relay that looks identical, but is wired differently internally.

Some troubleshooting advice here:
http://forums.pelicanparts.com/porsche-911-technical-forum/200561-1982-911sc-targa-cis-frequency-valve-chech-post1701553.html

[don gilbert]

you have to use the metal cased porsche relay, it is not the same as your standard five pin relay that you can get at any parts store. (some will work but not for very long) check your connection at the f/valve, it comes loose easy if the clip is gone, check the ecm gang connection behind the blower assy. clean your ecm ground under the pass seat, if no help, look at bently and follow the circut, could be a bad ecm ( i went through 3 before i found a good one)

[unclebilly]

See the for sale section, I have a complete cis system for sale off of a good running car.

[transformer]

Thanks for the help, The relay I replaced the metal case one is plastic. Also how do I know if the ECM is working and is it under the passenger seat?

[emcon5]

Originally Posted by transformer

Also how do I know if the ECM is working and is it under the passenger seat?

Yes, it is under the passenger seat.

Read the thread I linked above.

Tom

[don gilbert]

first you need the correct relay, and a dwell meter for accuracy, but you can feel the f/valve buzzing when you lay your hand on it. You need to read the Bentley to get a better understanding of how your 02 system works, its pretty simple, and clean all the gounds under the seat good, that fixes thing somtimes, but you need the right relay.

[don gilbert]

one more thing, at wot, your f/valve lowers the pressure in the lower diff chambers of your fuel dist. , which richins you mix, if not working, watch out for a lean situation. (not good)

[pjo046]

Hi!

You say that the engine is running fine, it's just the acceleration that isn't as it should be? Check your distributor to see if the mechanical advance is working. If this is stuck, your ignition won't advance much as the rpms increase, and thus the engine won't develop much power. This problem is present on my distributor, that's why I am mentioning it. Take the cap of your distributor, and ensure that the rotor can be rotated a bit. If not, your mechanical advance isn't working.

For a more thorough explanation on how to fix the problem (if it turns out your distributor isn't working as good as it should), just check out my thread on timing the ignition as several members have shared their wisdom there.

[Gunter]

Originally Posted by unclebilly

See the for sale section, I have a complete cis system for sale off of a good running car.

Uncle,

Your system is for a non-Lambda engine (No FV) and will only work on '77, '78 and '79 US or '78-'83 Euro engines.

It will not work for a US '82 or any US '80-'83 SC where Air Care is required.

[unclebilly]

Originally Posted by Gunter

Uncle,

Your system is for a non-Lambda engine (No FV) and will only work on '77, '78 and '79 US or '78-'83 Euro engines.

It will not work for a US '82 or any US '80-'83 SC where Air Care is required.

You should buy it from me...

[transformer]

I tested the the 35 pin connector and and I got the following reads:

5- open-problem?
6- grd
8- 12v
15-12v
16-grd

On the OXS relay connector:

30-12v
86-grd, problem?

with the OXS relay unpluged the car starts and runs smooth, when plugged in the motor shutters and stalls.

Same thing happens wehen the OXS control unit is disconnected and the OXS relay is plugged in.

Could the ground on 86 on the OXS relay be the problem?

[emcon5]

From the other thread:

Originally Posted by john walker's workshop

relay test. with 3 jumper wires,
ground 85,
12V to 30,
then jump 12V to 86 to activate it. it should click.
the relay should then be giving 12V to 87 which goes to the computer, and 12V to 87b, which goes to the frequency valve and enrichment relay.

following this advice, you could simply give 12V to the 87 and 87b terminals (both at the same time) on the relay plug to see if the frequency valve starts to buzz. engine needs to be running when this is done or you won't notice anything.

30 is hot
85 is ground
86 is the trigger, comes from the Lamda brain.
When the relay is active, you should get 12V from 87 and 87b

The wiring diagram is here:

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_Part6-1.jpg
http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_Part6-2.jpg Relay is on page 2

[emcon5]

Originally Posted by transformer

I tested the the 35 pin connector and and I got the following reads:

5- open-problem?

Missed this one. Loren's comments from the other thread, plus a look at the wiring diagram say that it is a problem.

Originally Posted by Lorenfb

This thread has become too complex!

It's VERY simple to checkout the Lambda control unit on a 911SC:

1. It must have a ground on pins 5 & 16 on the 35 pin Lambda connector.
2. It must have +12 volts on pins 8 & 15 (freg valve), (key on).
3. If you ground pin 15 with the engine running, it goes rich and idles poorly (unit disconnected).
This checks the freq valve.

If the above check out, the Lambda unit is bad. If you need it tested/rebuilt, send it to Pelican.
If they don't, use the diagram on this thread for wiring/relay troubleshooting.

That's it. It's that simple. Let's not make it a life time project!

For more info check out this web site (www.systemsc.com) on the Diagnostics page.

[don gilbert]

if you unplug the relay and the idle changes, then your f/valve is working. the whole purpose of the 02 system is to keep the fuel mix at stoich at idle and part throttle, and it does this by increasing and relieving the fuel pressure in the lower chambers of your fuel dist. at a very fast rate, the f/valve is just an inline injector that bleeds of press. when the ecm tells it to

[transformer]

I tested the circuit leaving the Lambda control to the engine and pin 5 of the control is not grounded and there is a ground either on the WUR or pin 30 on the fuel pump relay.

Does anybody know where the most common grounded wire problems occur?