Can't measure due cycle/dwell...help!
 

I've tried two meters so far. One digital and one analog and can't get a reading off either.
Both are two lead meters. I'm connecting the black to ground and the other lead to the green/white wire on the test port. What am I doing wrong, or what might not be working correctly? Could the test port be kaput? Thanks.

I was able to find an earlier thread where this is discussed - hope you find it a bit helpful.

http://forums.pelicanparts.com/porsche-911-technical-forum/479271-dwell-test-port-fv-duty-cycle-question.html

Thanks Dmitry,

This is the way I hooked my meter up (per the thread) and I get no reading.

fv duty cycle
 

if the system is not working you wont get a reading. lift the sensor plate slightly or disconnect the fuel pump safety switch connector with the key in the on position and you should here the FV buzzing. i am assuming you are working on a lambda cis system, if its an 80-83 sc , and you dont here it buzzing see if your interior light is working, the oxy system and interior light are on the same fuse

I did a little more troubleshooting tonight. I can hear a buzz from the FV (I'm assuming the fuel injectors don't give off the same kind of buzz?). I removed the passenger seat to take a better look at the lambda system. I checked all the connections and they are clean. With the car running, I disconnected the O2 relay and nothing changes. The weird thing is if I disconnect the O2 sensor in the engine bay the idle changes (drops a little but doesn't run rough really)? What gives?

FV duty cycle
 

what year is the car , also to answer your question about the harness i have seen a few with broken wires behind the protective boot of the test port

Car is an 82 US SC.
Is it possible to measure duty cycle directly at the lambda box off of pin 17?

i would do a continuity test first

you said you disconnected the relay under the pass seat, there are two relays on 81-83 sc the large one is accelleration enrichment and the little one is power supply. if you disconnect the little one or just unplug the control unit while it is running there should be a substantial drop in idle speed and throttle response should be sluggish and engine down on power if the system is working. as far as testing at the control unit you should be able to but you would have to remove the cover for the terminals

+1

Made a video many years ago demonstrating this. Near end you can hear muffled backfires.

<iframe width="560" height="315" src="https://www.youtube.com/embed/5tdpCYyvqSc" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

I definitely have no change when I unplug the O2 relay. No change in idle, no clicks, nuthin'. I ordered a new one today. Just to be safe I got the Porsche one. The one currently in the car is definitely original. My car has cold start and warmup issues. I found an old post on search where Pete Zimmerman indicated that erratic cold starts and warmup issues were also classic signs of a bad O2 relay.
I'll also plan to do step by step electrical checks of the lambda system. There Amy be other issues besides the relay one.

did you check the interior light fuse

Check the circuit. OXY Fuse for starters. Is the trunk light on when you lift the hood? You don't need step by step if basic.

Hi Bob and proporsche...the fuse is good. All the trunk and interior lights work.

Hi Bob and porschyard...the fuse is good. All the trunk and interior lights work.